B vitamins and cardiovascular health: mechanisms, clinical evidence, and precision prevention strategies

Abstract

Background

Cardiovascular diseases is the most common cause of mortality in the world. B vitamins (B₁–B₁₂) control how mitochondria make energy, how nitric oxide is made, how one-carbon is used, and how genes work. A deficiency leads to hyperhomocysteinemia, oxidative stress, and endothelial dysfunction, all of which are important to vascular disease. Observational studies consistently associate low B-vitamin levels with an elevated risk of cardiovascular diseases; nevertheless, randomized supplementation trials have demonstrated only modest reductions in significant events.

Methods

This narrative review summarizes molecular, epidemiological, and clinical evidence on the role of B vitamins in cardiovascular health. Special focus was paid to functional biomarkers and gene-nutrient interactions that affect how well a therapy works. The literature was identified through targeted searches of PubMed, Scopus, and Google Scholar. Priority was given to high-quality evidence, including mechanistic studies, observational cohorts, randomized controlled trials, meta-analyses, and major review articles relevant to cardiovascular outcomes.

Results

Functional indicators, such as methylmalonic acid and holotranscobalamin, offer superior accuracy compared to blood levels in assessing vitamin status. Nutrigenetic interactions, particularly the effects of folate and riboflavin on methylenetetrahydrofolate reductase polymorphisms, exhibit blood pressure-lowering and stroke-preventive advantages. The clinical efficacy of B-vitamin supplementation is highly dependent on baseline nutritional status and regional food fortification policies. For example, folic acid supplementation significantly reduces stroke incidence in populations who lack mandatory folate fortification, whereas trials conducted in folate-sufficient cohorts generally demonstrated no added cardiovascular benefit. Recognizing this population-specific variability helps explain the historical discrepancy between the strong mechanistic potential of B-vitamins and the mixed results observed in large-scale clinical trials.

Conclusion

While adequate B-vitamin status remains mechanistically essential for cardiovascular homeostasis, the clinical benefits of routine supplementation are nuanced and highly population-dependent. Consequently, ubiquitous supplementation is unlikely to produce extensive advantages. A precision strategy that combines biomarkers, genotype stratification, and population context can help find their therapeutic potential. Future methods should integrate diet with precision cardiology to enhance vascular prevention.

Introduction

Cardiovascular diseases (CVD) remain the leading cause of mortality globally. It results in approximately 19 to 20 million fatalities annually, constituting nearly one-third of all deaths [1]. Despite advancements in medical therapies and preventive measures, the incidence of cardiovascular diseases (CVD) continues to rise due to an aging and expanding population [2]. Hypertension, diabetes, dyslipidemia, obesity, and smoking remain the principal modifiable risk factors for the prevention of heart disease. Nevertheless, increasing evidence highlights the importance of additional, non-conventional factors, such as nutritional status and micronutrient accessibility, in affecting vascular health and cardiometabolic outcomes.

Among these non-conventional factors, the B-vitamin family has attracted increasing interest. The eight B-vitamins: thiamine (B₁), riboflavin (B₂), niacin (B₃), pantothenic acid (B₅), pyridoxine (B₆), biotin (B₇), folate (B₉), and cobalamin (B₁₂) are essential, water-soluble cofactors that modulate vital aspects of human metabolism. Their metabolic roles include mitochondrial oxidative phosphorylation, fatty acid β-oxidation, one-carbon metabolism, and methylation processes vital for DNA synthesis and epigenetic regulation [3]. Although these functions are fundamental to overall cellular metabolism, only some of these pathways directly influence cardiovascular physiology. B-vitamins influence the bioavailability of endothelial nitric oxide, the equilibrium of redox processes, inflammatory signaling, and the remodeling of blood vessels, either directly or indirectly. In many cases, their cardiovascular effects arise from both direct vascular mechanisms and indirect improvements in systemic metabolic health. Deficiencies in particular B-vitamins have been associated with diverse cardiovascular phenotypes, such as hyperhomocysteinemia, arterial stiffness, compromised mitochondrial energetics, and dyslipidemia [4, 5].

The growing recognition of B vitamins as modulators of cardiovascular health raises important scientific and clinical questions. Epidemiological studies have frequently reported that inadequate B-vitamin levels are associated with an elevated risk of coronary artery disease, stroke, and heart failure [4, 6]. Clinical supplementation trials have yielded mixed results: some report improvements in endothelial function and reductions in stroke incidence, particularly in populations without folate fortification [7, 8], whereas others failed to demonstrate hard outcome benefits in the statin era [9]. This inconsistency may partly reflect the challenge of distinguishing direct cardiovascular effects from broader systemic metabolic influences of B-vitamin status. At the same time, mechanistic advances have revealed novel roles for B-vitamins in pathways such as epigenetic regulation, NAD⁺ metabolism, and gene nutrient interactions, highlighting that their cardiovascular effects are likely context-specific and influenced by genetic, metabolic, and environmental factors [10].

Despite these mechanistic and clinical advances, recent literature lacks a unified synthesis that bridges the historical focus on homocysteine with emerging paradigms in precision cardiology. Previous reviews have frequently examined B vitamins in isolation or focused exclusively on broad population-level stroke prevention. Therefore, a critical knowledge gap remains regarding the integration of novel functional biomarkers (e.g., holotranscobalamin and methylmalonic acid) and nutrigenetic interactions (such as MTHFR polymorphisms) across the entire spectrum of B-complex vitamins. To address this gap, this review aims to synthesize molecular insights, preclinical data, demographic research, and clinical trial results to rigorously evaluate the role of B-vitamins in cardiovascular health. We seek to examine each vitamin from B₁ to B₁₂ to elucidate their biochemical foundations, the vascular and metabolic ramifications of deficiency, and their therapeutic potential in prevention and treatment.

Biochemistry and physiology of B vitamins

B vitamins are water-soluble nutrients essential for numerous metabolic and physiological activities. They perform essential functions as coenzymes in metabolic processes such as energy production, DNA synthesis, maintenance of redox equilibrium, and preservation of brain health. This section discusses the various functions of B vitamins, their synergistic interactions inside the body, and recent studies that associate them with cardiovascular health and disease (Fig. 1).

Fig. 1.

Summary of major biochemical functions of individual B-vitamins in cardiovascular physiology. Thiamine (B1) supports ATP generation, riboflavin (B2) regulates mitochondrial redox reactions and nitric oxide synthase activity, niacin (B3) provides NAD⁺ for energy and lipid metabolism, pantothenic acid (B5) forms coenzyme A, pyridoxine (B6) regulates homocysteine catabolism, biotin (B7) supports carboxylase reactions, folate (B9) underpins nucleotide synthesis and DNA methylation, and cobalamin (B12) remethylates homocysteine to methionine

Vitamin B1 (thiamine)

Thiamine (vitamin B1) is crucial for cardiac metabolism, serving as thiamine pyrophosphate, a key cofactor for the pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes. The myocardium predominantly depends on aerobic metabolism; thus, even minor deficiencies hinder oxidative phosphorylation and ATP synthesis, resulting in energy depletion, lactate buildup, and ultimately, contractile dysfunction. Soukoulis et al. found that thiamine deficiency adversely affects myocardial energetics and induces acidosis, which are mechanisms responsible for the cardiac manifestations of wet beriberi and play a role in the progression of heart failure [11].

Furthermore, thiamine pyrophosphate serves as an essential cofactor for transketolase, which is a critical enzyme in the non-oxidative branch of the pentose phosphate pathway. This pathway is vital in generating NADPH, which is required for maintaining intracellular redox homeostasis, regenerating reduced glutathione and supporting endothelial nitric oxide synthase (eNOS) function. Consequently, the impaired transketolase activity during thiamine deficiency limits the antioxidant capacity of the myocardium thus exacerbating oxidative stress and contributing to the structural and functional myocardial impairments that are seen in heart failure [12].

Animal studies have corroborated these metabolic disturbances. McCandless et al. revealed that rats experiencing dietary thiamine deficiency had a gradual depletion of myocardial ATP stores, resulting in significant declines in cardiac contractility [13]. Similarly, Han et al. showed that cardiomyocytes exposed to low amounts of thiamine exhibited mitochondrial dysfunction, impaired contractile reserve, and heightened susceptibility to stress, whereas supplementation preserved ATP production and improved myocardial performance [14]. All of these findings point to the importance of thiamine in preserving the heart’s mitochondrial integrity and energy metabolism.

In clinical practice, thiamine deficiency is often associated with the administration of loop diuretics, which enhance urine excretion. Sica et al. stressed that patients who are on furosemide for a long time are especially vulnerable, which suggests that a lack of thiamine may make systolic dysfunction worse in this group [15]. However, Teigen et al. reported that the incidence of laboratory-confirmed thiamine deficiency in stable outpatients with heart failure was comparatively low, with no correlation identified between deficiency, diuretic dosage, or left ventricular function, suggesting that the clinical significance of deficiency may vary by context [16].

Numerous interventional studies have assessed the therapeutic thiamine supplementation. Shimon et al. indicated that patients with chronic heart failure administered high-dose furosemide exhibited enhancements in left ventricular ejection fraction (LVEF) and clinical symptoms subsequent to intravenous thiamine treatment, followed by oral maintenance therapy [202]. Conversely, Smithline et al. saw no substantial advantage from the acute administration of thiamine to hospitalized patients with decompensated heart failure, underscoring variability in response based on patient selection and timing [17]. Mousavi et al. recently performed a double-blind randomized trial involving patients with systolic heart failure. Their findings indicated that, although there was no significant improvement in overall left ventricular ejection fraction (LVEF), supplementation did enhance septal and lateral tissue velocities and decrease peripheral edema, implying functional advantages beyond ejection fraction [203].

He et al. conducted a meta-analysis that synthesized these findings, concluding that although thiamine supplementation reliably rectified biochemical deficiency, its effects on clinical outcomes, including LVEF, ventricular volumes, natriuretic peptide levels, and functional status, were minimal and statistically insignificant [18]. Nonetheless, epidemiological data from Wen et al. indicate that increased dietary thiamine intake correlates with a markedly diminished risk of heart failure and cardiovascular mortality in extensive population cohorts, underscoring the potential preventive significance of sufficient thiamine levels [19].

The existing evidence suggests that thiamine deficiency can lead to significant myocardial energetic failure and structural remodeling, especially during diuretic treatment. Although supplementation has shown biochemical rectification and certain functional enhancements, outcomes across clinical trials are inconsistent. Comprehensive, well-structured randomized controlled trials are essential to ascertain if targeted thiamine supplementation should be routinely included in heart failure care, especially for patients utilizing loop diuretics or those at elevated risk for nutritional deficiencies.

Collectively, these findings highlight that thiamine deficiency directly impairs myocardial energetics and redox balance, processes that are central to the development and progression of cardiovascular diseases.

Vitamin B2 (riboflavin)

Building on the role of thiamine in myocardial energy metabolism, riboflavin further supports cardiovascular function through its involvement in mitochondrial respiration and redox homeostasis. Riboflavin serves as the precursor for FMN and FAD, essential cofactors for numerous human flavoenzymes critical to mitochondrial energy metabolism and redox regulation. Lienhart et al. documented the “human flavoproteome,” highlighting the presence of FMN in complex I and FAD in complex II among several energy-producing enzymes, emphasizing the influence of riboflavin levels on cellular respiration [20].

Beyond its established role in mitochondrial flavoprotein metabolism, riboflavin contributes to cellular redox regulation through the glutathione system. Powers et al. demonstrated that riboflavin, as the precursor of FAD, is required for the activity of glutathione reductase, the NADPH-dependent enzyme responsible for regenerating reduced glutathione (GSH) from its oxidized form (GSSG) [21]. In line with this, Olfat et al. showed that impaired riboflavin status reduces glutathione reductase activity and promotes a shift toward an oxidized intracellular environment [22]. Given that GSH represents the predominant intracellular thiol antioxidant and a key determinant of endothelial redox balance, disruption of this pathway contributes to oxidative stress, endothelial dysfunction, and cardiovascular pathology [23]. Furthermore, Forman et al. highlighted the central role of the glutathione system in maintaining vascular homeostasis [24]. Collectively, these findings indicate that riboflavin influences vascular and myocardial health not only through energy metabolism but also via direct modulation of the glutathione redox cycle. These redox-dependent mechanisms complement the role of riboflavin in nitric oxide signaling and mitochondrial bioenergetics. Förstermann et al. showed that all nitric oxide synthase isoforms, including eNOS, require FMN and FAD, establishing a mechanistic link between riboflavin biology and vascular tone via NO bioavailability [25]. A recent review summarizes how FAD/FMN-dependent pathways connect riboflavin to energy metabolism and redox equilibrium across tissues [26].

Based on these biochemical findings, Peng et al. found that riboflavin improves pathological cardiac hypertrophy in mice by increasing myocardial FAD and activating short-chain acyl-CoA dehydrogenase (SCAD). This leads to better ATP production and less fibrosis; however, knocking down SCAD had the opposite effect [27]. Concurrently, Xu et al. demonstrated in a heart-failure model that riboflavin elevates FAD, activates SCAD, mitigates oxidative stress and cardiomyocyte apoptosis, and engages DJ-1–Keap1–Nrf2 signaling, together resulting in cardioprotection [28]. Wang et al. previously showed in streptozotocin-diabetic rats that oral riboflavin enhanced left-ventricular systolic and diastolic function, increased SOD and HO-1 levels, and reduced lipid peroxidation and connective-tissue growth factor, indicating synergistic bioenergetic and antioxidant advantages [29].

Evidence for vascular protection is also evident beyond the heart. Yu et al. reported that oral riboflavin enhanced endogenous superoxide dismutase activity and reduced abdominal aortic aneurysm formation in rats, evidenced by decreased reactive oxygen species and DNA oxidation in the aorta wall, thus providing direct support for antioxidant-mediated vascular effects in vivo [30]. At the inflammatory interface, Ahn et al. demonstrated that riboflavin attenuates NLRP3 and other inflammasome activities, thereby diminishing IL-1β/IL-18 secretion in macrophages and in mouse peritonitis, establishing a connection between riboflavin and the inhibition of caspase-1–dependent signaling and mitochondrial danger signals that contribute to vascular inflammation [31].

Clinical investigations demonstrate a significant, genotype-specific impact on blood pressure. Wilson et al. documented in a focused randomized trial that hypertensive individuals possessing the MTHFR 677TT genotype exhibited substantial reductions in blood pressure with low-dose riboflavin, corroborating FAD’s function as the MTHFR cofactor; a 4-year follow-up substantiated the persistence of this response [32]. Ward et al. found that the 677TT genotype increased the risk of hypertension at the population level, and that improved riboflavin status mitigated this heightened risk, suggesting a nutrigenetic interaction [33]. Rooney et al. demonstrated that persons possessing the 677TT genotype exhibit elevated brachial and central (aortic) pressures compared to non-TT counterparts, underscoring a hemodynamic phenotype potentially influenced by riboflavin status [34].

These mechanisms suggest that riboflavin status may influence vascular tone, oxidative stress, and endothelial function, all of which are key determinants of cardiovascular disease risk.

Vitamin B3 (niacin)

In addition to redox regulation, niacin contributes to cardiovascular health through its central role in NAD⁺ metabolism and lipid regulation. Niacin (vitamin B₃) is the dietary precursor for nicotinamide adenine dinucleotide (NAD⁺) and its phosphorylated form NADP⁺, which are essential cofactors in redox metabolism, mitochondrial respiration, and lipid biosynthesis. Pirinen et al. showed that giving niacin supplements to people with mitochondrial myopathy greatly increased systemic NAD⁺ levels, increased mitochondrial gene expression, improved oxidative metabolism, and even decreased the amount of fat in the liver. This is strong evidence for niacin’s ability to improve mitochondrial function in humans [35].

In the liver, niacin plays a pivotal role in lipid regulation. Ganji et al. found that niacin reduced the buildup of lipids caused by palmitate in cultured human hepatocytes by blocking the expression of diacylglycerol acyltransferase-2 (DGAT2), lowering reactive oxygen species, and lowering interleukin-8 secretion. This suggests that niacin has both anti-steatotic and anti-inflammatory effects [36]. Supporting these experimental findings, Zhou et al. analyzed population data and found a U-shaped association between dietary niacin intake and the prevalence of metabolic dysfunction–associated steatotic liver disease, with an optimal intake around 23.6 mg/day conferring the lowest risk [37].

Niacin’s cardiovascular advantages were established decades ago as a result of its unique lipid-modifying properties. Pharmacologic doses lower LDL cholesterol and triglycerides while considerably increasing HDL cholesterol, resulting in a general improvement in lipid profiles. In the ARBITER 2 trial, Taylor et al. discovered that adding extended-release niacin to statin medication not only enhanced HDL-C levels but also led to regression of carotid intima-media thickness, a hallmark of atherosclerosis progression [38]. Similarly, Villines et al., in the ARBITER 6–HALTS study, reported that niacin plus statins was superior to ezetimibe plus statins in halting carotid atherosclerosis progression, reinforcing niacin’s vascular protective effects [39]. Earlier, the HATS trial demonstrated that simvastatin combined with niacin, with or without antioxidants, produced regression of coronary lesions and markedly reduced cardiovascular events compared to placebo or antioxidants alone [40].

However, enthusiasm was dampened in the modern statin era. In the AIM-HIGH trial, Boden et al. examined high-dose extended-release niacin in individuals with pre-existing cardiovascular diseases, low HDL-C levels, and well-regulated LDL-C levels while on statins. Although niacin improved HDL-C and triglycerides, it didn’t reduce the cardiovascular events any more than it already was. The trial was discontinued early due to lack of efficacy and concerns about increased ischemic stroke risk [41].

In addition to its lipid effects, niacin affects inflammation and age-related metabolic deterioration. Mechanistic investigations indicate that niacin can regulate sirtuin-1 (SIRT1) activity and suppress NF-κB activation, therefore diminishing vascular inflammation and oxidative stress [42]. Importantly, sirtuins are NAD⁺-dependent class III deacetylases, thereby establishing a direct biochemical link between niacin-derived NAD⁺ availability and cardiovascular regulation. As reported by Imai et al. [43], sirtuin activity is tightly dependent on intracellular NAD⁺ levels, positioning niacin as a key regulator of these enzymes. Among sirtuins, SIRT1 plays a central role in vascular homeostasis through deacetylation of multiple protein targets. Mattagajasingh et al. [44] demonstrated that SIRT1-mediated deacetylation of endothelial nitric oxide synthase (eNOS) enhances nitric oxide bioavailability and improves endothelial function. In addition, Yeung et al. [45] reported that SIRT1 suppresses pro-inflammatory signaling through deacetylation of nuclear factor-κB (NF-κB). Furthermore, Rodgers et al. [46] showed that SIRT1 regulates mitochondrial biogenesis and energy metabolism via activation of peroxisome proliferator–activated receptor gamma coactivator-1α (PGC-1α), while also modulating antioxidant defenses through forkhead box O (FOXO) transcription factors. Collectively, these findings indicate that niacin, through its role in NAD⁺ synthesis, may exert pleiotropic cardioprotective effects via SIRT1-mediated deacetylation pathways, extending beyond its classical lipid-modifying properties.

Beltrà et al. showed in cancer cachexia models that niacin administration restored NAD⁺, mitochondrial function, and enhanced survival, highlighting its therapeutic potential in extreme metabolic stress [47]. In parallel, Lapatto et al. demonstrated that supplementation with the niacin derivative nicotinamide riboside safely elevated NAD⁺ levels and enhanced mitochondrial activity in both healthy and older persons, indicating its potential in mitigating age-related metabolic decline [48].

Overall, niacin sits in a unique position in cardiovascular medicine: as a traditional lipid-altering agent with proven atheroprotective effects in the past, and as a contemporary NAD⁺-boosting nutrient with possible functions in mitochondrial health, hepatic lipid control, and vascular inflammation. Although large outcome trials such as AIM-HIGH have limited its broad therapeutic application with statins, continued interest in NAD⁺ metabolism and new precursors such as nicotinamide riboside suggest that niacin will remain relevant in cardiovascular and metabolic research. Together, these pathways position niacin as a modulator of lipid metabolism, inflammation, and mitochondrial function, linking it directly to cardiovascular disease mechanisms.

Vitamin B5 (pantothenic acid)

Complementing these metabolic pathways, pantothenic acid supports cardiovascular function through its role in coenzyme A-dependent energy metabolism. Pantothenic acid, also known as vitamin B₅, is the sole dietary precursor of coenzyme A (CoA), a molecule indispensable for fatty acid β-oxidation, the tricarboxylic acid cycle, and the biosynthesis of cholesterol and acetylcholine. Because of its central role in intermediary metabolism, CoA is especially important in the myocardium, where mitochondrial respiration must adapt rapidly to meet high energetic demands. Czumaj et al. emphasized that pantothenic acid deficiency compromises this pathway, impairing mitochondrial function and cellular metabolism in energy-intensive tissues such as the heart [49].

Experimental research has demonstrated the metabolic consequences of pantothenic acid deficiency. Smith showed that animals receiving pantothenic acid-deficient diets had big drops in tissue CoA levels, with a 38% drop in heart muscle. These animals had impaired fatty acid oxidation, reduced glycogen reserves, and decreased endurance under stress, underscoring the dependence of cardiac function on adequate CoA availability [201]. Building on this molecular connection, Audam et al. found that specifically blocking pantothenate kinase, the enzyme that slows down CoA biosynthesis, worsened ventricular dysfunction in pressure-overload models. This directly linked CoA depletion to maladaptive cardiac remodeling [50].

While interventional cardiovascular trials are absent, epidemiological evidence indicates a beneficial correlation between vitamin B₅ level and cardiovascular diseases. Sun et al. investigated plasma pantothenic acid concentrations in individuals undergoing coronary angiography and identified a significant L-shaped correlation with coronary heart disease. People with plasma vitamin B₅ levels in the third quartile (34.9–44.0 ng/mL) had a 58% lower risk than those in the lowest quartile, and people with levels in the highest quartile (≥ 44.0 ng/mL) had a 51% reduced risk. The benefit was most pronounced in persons with lower baseline levels and was especially significant among current and past smokers, indicating that adequate vitamin B₅ levels may reduce atherosclerosis risk in susceptible populations [51]. These findings suggest that adequate pantothenic acid levels are important for maintaining myocardial energy homeostasis and may influence cardiovascular disease susceptibility.

Vitamin B6 (pyridoxine)

Beyond energy metabolism, vitamin B₆ plays a key role in amino acid metabolism and homocysteine regulation, linking it closely to vascular health. Vitamin B₆, primarily in its active coenzyme form pyridoxal-5′-phosphate (PLP), participates in numerous enzymatic reactions, including transamination, decarboxylation, and the metabolism of homocysteine. Deficiency of PLP has long been linked to hyperhomocysteinemia, a recognized risk factor for cardiovascular diseases, because elevated homocysteine promotes endothelial dysfunction, oxidative stress, and vascular inflammation. Minović et al. highlighted that PLP deficiency results in defective one-carbon metabolism and homocysteine accumulation, leading to atherogenesis and cardiovascular risk [52].

Epidemiological studies support this link. Lin et al. found that Taiwanese adults with plasma PLP < 30 nmol/L had an 85% greater risk of coronary artery disease than those with higher levels, even after controlling for confounders such as smoking and cholesterol levels [53]. Likewise, Hu et al. found in a large Chinese cohort that plasma PLP was inversely associated with coronary heart disease risk, with each doubling of PLP associated with a 28% lower risk overall and a 37% lower risk in women [54].

Mechanistic work in animal and cellular models supports these observations. Stach et al. showed that vitamin B₆ deficiency caused endothelial dysfunction through increased expression of vascular adhesion molecules (VCAM-1) and pro-inflammatory cytokines (IL-6), whereas PLP supplementation reduced these inflammatory pathways and improved endothelial function [55]. PLP also inhibited NLRP3 inflammasome activation and IL-1β production in the same study, suggesting its protective effect against chronic vascular inflammation.

Vitamin B₆ may also affect oxidative stress and thrombosis. In vitro studies indicate that deficiency enhances ROS and platelet aggregation, while PLP supplementation has antiplatelet and endothelial-protective effects. Reeve et al. offered supporting evidence in animal models, demonstrating that pyridoxamine, a natural form of vitamin B₆, decreased age-related arterial stiffening and improved vascular function in old mice, indicating a potential role in vascular aging [56].

Population-based studies corroborate these results. Huang et al. analyzed NHANES data and found that greater dietary vitamin B₆ intake was associated with a significantly lower prevalence of CVD, with men in the highest intake quartile having 23% lower odds of CVD and women 27% lower odds, compared with the lowest quartile [57].

Although there are limited RCTs on B₆ alone, the combination of B₆, B₁₂, and folate supplementation has been associated with vascular benefits. Schnyder et al. demonstrated that this combination reduced plasma homocysteine and enhanced endothelial function in patients with coronary artery disease, suggesting a synergistic effect of B-vitamins on cardiovascular protection [58].

The vascular effects of combined B-vitamin supplementation differ mechanistically from those of individual vitamins due to their coordinated roles in one-carbon metabolism and homocysteine clearance. As reported by Lonn et al. [59], combined supplementation with folic acid, vitamin B₆, and vitamin B₁₂ significantly reduced plasma homocysteine levels in high-risk cardiovascular patients, although this did not translate into a proportional reduction in major cardiovascular events. Mechanistically, folate and vitamin B₁₂ facilitate the remethylation of homocysteine to methionine via methionine synthase, whereas vitamin B₆ serves as a cofactor for cystathionine β-synthase in the transsulfuration pathway, promoting its conversion to cysteine. This complementary metabolic interaction enables more effective homocysteine reduction than monotherapy. In line with this, Martí-Carvajal et al. [60] demonstrated in a Cochrane systematic review that while combined B-vitamin therapy consistently lowers homocysteine levels, its impact on cardiovascular outcomes remains variable, suggesting that biochemical improvement does not always translate into clinical benefit. Collectively, these findings indicate that the vascular effects of B-vitamin supplementation are largely dependent on their integrated metabolic actions rather than isolated effects, underscoring the importance of considering these vitamins as a functional biochemical network in cardiovascular prevention.

Vitamin B7 (biotin)

In contrast to other B vitamins, the cardiovascular role of biotin is less well defined and appears to be primarily indirect through metabolic regulation. Biotin is an essential coenzyme for carboxylase enzymes that are involved in the synthesis of fatty acids through acetyl–CoA carboxylase, the catabolism of amino acids, and gluconeogenesis through pyruvate carboxylase. In metabolically active organs such as the heart and liver, these pathways directly contribute to energy homeostasis. The Linus Pauling Institute overview emphasizes the central role of biotin in these fundamental metabolic processes and suggests that it may have broader systemic implications, such as vascular function [61].

In a high-fructose diet model of metabolic syndrome in rodents, Aguilera-Méndez et al. researched the effects of biotin supplementation in experimental settings. They showed that biotin improved insulin resistance, suppressed hepatic lipid accumulation, reduced oxidative damage, and prevented associated increases in blood pressure, thereby supporting a protective metabolic role with potential vascular implications [62].

At the molecular level, recent mechanistic reviews, such as those conducted by Sakurai-Yageta et al., have underscored the emerging functions of biotin in metabolic regulation and inflammation at the molecular level. In particular, biotin supplementation has been demonstrated to suppress the production of pro-inflammatory cytokines, potentially through the modulation of pathways such as mTOR. This suggests that there are indirect benefits for vascular health and inflammation [63].

Although there’s growing interest in biotin’s broader biological roles, strong evidence connecting biotin directly to endothelial nitric oxide production, vasodilation, or flow-mediated dilation in humans is currently lacking.

Vitamin B9 (folate)

Folate represents one of the most extensively studied B vitamins in cardiovascular research due to its central role in one-carbon metabolism. Folate underpins one-carbon metabolism: as 5-methyltetrahydrofolate (5-MTHF), it donates a methyl group to homocysteine via methionine synthase, sustaining DNA synthesis/methylation and keeping homocysteine in check, processes that are central to vascular health. Pushpakumar et al. reviewed how folate deficiency drives hyperhomocysteinemia and endothelial injury, while classic human studies by Blount et al. and Linhart et al. showed that folate depletion causes uracil misincorporation, DNA strand breaks, and impaired thymidylate synthesis mechanisms that can compromise endothelial cell proliferation and repair [64–66].

Building on this biology, Antoniades et al. demonstrated in human vessels that 5-MTHF rapidly improves endothelial function by restoring tetrahydrobiopterin (BH4) bioavailability and re-coupling eNOS, thereby reducing vascular superoxide; complementary biochemical work by Stroes et al. showed that folate can directly normalize dysfunctional eNOS, clarifying a homocysteine-independent route to better NO signaling [67, 68]. In people, folate consistently improves conduit-artery physiology. Woo et al. reported that folic acid enhanced brachial artery flow-mediated dilation (FMD) in adults with hyperhomocysteinemia, and subsequent trials plus meta-analyses confirmed clinically meaningful FMD gains with folic acid supplementation [69–71].

Translational and experimental data point to anti-inflammatory and anti-atherosclerotic actions. In ApoE−/− mice, folic acid supplementation slowed atherosclerotic lesion development and altered methylation of athero-relevant genes such as MCP-1 and VEGF, while in diet-induced hyperhomocysteinemia, folate lowered aortic VCAM-1 expression, consistent with reduced endothelial activation [72, 73].

Critically, outcome trials and population data align with these mechanistic and physiological benefits. In the China Stroke Primary Prevention Trial (CSPPT), Huo et al. found that adding folic acid to antihypertensive therapy reduced the risk of first stroke by 21% among hypertensive adults without folate fortification, an effect that was strongest in those with low baseline folate [74]. After mandatory grain fortification in the United States and Canada, Yang et al. observed an accelerated decline in stroke mortality versus England/Wales (no fortification at that time), supporting a population-level vascular benefit [75]. Meta-analytic evidence further shows a modest reduction in stroke risk with folic acid supplementation, particularly where baseline folate status is low or fortification is absent [76].

Finally, developmental data suggest early-life vascular relevance: Martin et al. reported that newborn microvascular endothelial function correlates with folate status and birth weight, linking maternal fetal folate sufficiency to healthier neonatal vascular physiology [77].In sum, these strands molecular, physiological, animal, trial, and population converge on a cohesive picture in which folate (and specifically 5-MTHF) supports vascular integrity by sustaining nucleotide synthesis and methylation, enhancing NO bioavailability via eNOS/BH4 biology, and dampening endothelial activation; where background folate status is low, supplementation appears to translate these mechanisms into measurable reductions in stroke risk. These converging mechanisms establish folate as a key regulator of endothelial function and stroke risk, particularly in populations with low baseline folate status.

Vitamin B12 (cobalamin)

Closely interacting with folate, vitamin B₁₂ plays a complementary role in one-carbon metabolism and vascular function. Vitamin B₁₂ is central to one-carbon and mitochondrial metabolism: Mascarenhas et al. detailed that humans have only two cobalamin-dependent enzymes, methionine synthase (for homocysteine remethylation) and methylmalonyl-CoA mutase (for propionyl-to-succinyl-CoA conversion), so deficiency predictably raises homocysteine and methylmalonic acid (MMA), perturbing vascular biology [78]. Building on this mechanism, Hofmann et al. showed in hyperhomocysteinemic mice that vascular inflammation is amplified via NF-κB signaling, linking B-vitamin insufficiency to endothelial activation and atherogenesis [79].

Translating the mechanism to humans, Chambers et al. reported that folic acid plus vitamin B₁₂ lowered free plasma homocysteine and improved brachial artery flow-mediated dilation in patients with coronary heart disease, consistent with homocysteine-mediated endothelial dysfunction [80]. Willems et al. likewise observed improved coronary endothelial function after combined folate and cobalamin therapy in coronary disease [81]. Beyond combination therapy, Kwok et al. conducted a randomized, double blind, placebo-controlled crossover trial in vegetarians with low B₁₂, showing that cobalamin alone improved brachial FMD and reduced carotid intima media thickness over 12–36 weeks, an effect accompanied by rises in serum B₁₂ and falls in homocysteine [82]. Complementing these findings in a B₁₂-deficient elderly cohort, Kurt et al. found that folate plus B₁₂ improved coronary flow reserve while lowering homocysteine, reinforcing a functional vascular benefit where deficiency is present [83].

On the mitochondrial side, Schleicher et al. reviewed how B₁₂ deficiency drives accumulation of MMA and homocysteine with downstream oxidative stress and bioenergetic impairment pathways relevant to endothelial health [84]. Epidemiologically, Wang et al. reported that higher circulating MMA, often a sensitive marker of tissue-level B₁₂ deficit, was independently associated with cardiovascular diseases presence, plausibly via oxidative and mitochondrial mechanisms [85].

Lastly, cerebrovascular correlates align with this biology. Tangney et al. linked higher MMA and related B₁₂ markers with lower total brain volume and with cognitive performance; homocysteine’s cognitive associations were attenuated after accounting for white-matter hyperintensities and cerebral infarcts on MRI, supporting microvascular involvement [86].In an interventional context, Smith et al. (VITACOG) showed that homocysteine-lowering with high-dose folate, B₆, and B₁₂ slowed brain atrophy in older adults with mild cognitive impairment, a result consistent with protection of vulnerable small-vessel territories and metabolically active tissue [87].

Taken together, these findings highlight vitamin B₁₂ as a critical determinant of vascular health through its roles in homocysteine regulation, mitochondrial function, and endothelial integrity.

A detailed comparative summary of the biochemical roles, deficiency phenotypes, and clinical evidence for B vitamins (B1–B12) is presented in (Table 1). The evidence discussed in this section is derived from experimental and observational studies. Therefore, while these findings provide valuable mechanistic insights, they should not be interpreted as definitive evidence of clinical benefit, and their translation to cardiovascular outcomes in humans remains context-dependent.

Table 1.

Summary of biochemical roles, cardiovascular pathways, deficiency effects, and clinical/epidemiological evidence for B vitamins (B1–B12)

Vitamin	Biochemical role / cofactors	Metabolic & vascular pathways	Deficiency phenotypes	Clinical/trial findings	Epidemiological evidence
B1 (Thiamine) (11–18)	Cofactor (TPP) for PDH, α-KGDH, transketolase; ATP synthesis	Mitochondrial energetics; lactate metabolism; endothelial NO bioavailability	Wet beriberi, HF, acidosis, contractile dysfunction	IV/oral thiamine improved LVEF in CHF; mixed RCTs; possible tissue velocity gains	Cohorts show higher intake linked to ↓ HF and CVD mortality
B2 (Riboflavin) (19–29)	Precursor for FMN, FAD; flavoproteins in ETC, NO synthase	Oxidative phosphorylation; redox balance; MTHFR cofactor	Impaired respiration, endothelial dysfunction	Animal models: improved hypertrophy & HF outcomes; ↓ oxidative stress	MTHFR 677TT genotype: BP lowering with riboflavin supplementation
B3 (Niacin) (30–39)	Precursor for NAD+/NADP+; sirtuin regulation	Lipid metabolism, mitochondrial respiration, NF-κB inhibition	Dyslipidemia, pellagra	↑ HDL, ↓ LDL/TG; ARBITER & HATS: atheroprotection; AIM-HIGH no benefit in statin era	U-shaped association with liver steatosis; protective dietary intake
B5 (Pantothenic Acid) (40–42)	Precursor of CoA; fatty acid oxidation, TCA cycle	Mitochondrial bioenergetics, lipid metabolism	Energy depletion, impaired FA oxidation	No major RCTs; animal data: CoA depletion worsens HF remodeling	Coronary angiography cohorts: L-shaped protective association
B6 (Pyridoxine) (43–49)	PLP cofactor in transamination, homocysteine metabolism	Homocysteine clearance; vascular inflammation modulation	Hyperhomocysteinemia, endothelial dysfunction	RCTs: B6 + B12 + folate ↓ homocysteine, improved FMD	Large cohorts: PLP inversely associated with CHD risk
B7 (Biotin) (50–52)	Cofactor for carboxylases (acetyl-CoA, pyruvate, propionyl-CoA)	Gluconeogenesis, FA synthesis, and amino acid catabolism	Dermatitis, insulin resistance, and hypertension (animal)	Rodent studies: ↓ BP, improved insulin/lipid metabolism	Limited direct human vascular evidence
B9 (Folate) (53–66)	5-MTHF donor for homocysteine→methionine; DNA synthesis	Homocysteine regulation, eNOS coupling via BH4	Megaloblastic anemia, vascular dysfunction	CSPPT: ↓ first stroke by 21% with folic acid; improves FMD	Population fortification: ↓ stroke mortality; cohorts link to ↓ CVD
B12 (Cobalamin) (67–76)	Cofactor for methionine synthase, methylmalonyl-CoA mutase	Homocysteine remethylation, mitochondrial metabolism	Megaloblastic anemia, neuropathy, vascular dysfunction	Improves FMD in deficiency; ↓ CIMT in vegetarians; combo therapy benefits	Epidemiology: MMA levels predict ↑ CVD risk; deficiency linked to stroke risk

Pathophysiological Connections between B vitamins and cardiovascular diseases

B vitamin levels have been linked and implicated to have a role in cardiovascular health and disease progression. B vitamins influence cardiovascular health through several mechanisms, as B vitamins affect homocysteine metabolism and levels, epigenetics, oxidative stress and inflammation, and lipid metabolism (Fig. 2). The cardiovascular effects of B vitamins are mediated through several well-defined molecular pathways rather than generalized metabolic processes. Key mechanisms include endothelial nitric oxide synthase (eNOS) coupling and nitric oxide bioavailability, mitochondrial oxidative phosphorylation, redox regulation via the glutathione system, and epigenetic modulation through DNA methylation. In addition, signaling pathways such as NF-κB–mediated inflammation, Nrf2-dependent antioxidant responses, and homocysteine-induced endoplasmic reticulum stress further link B-vitamin status to vascular dysfunction. These mechanisms provide a more precise framework for understanding how B vitamins influence cardiovascular disease pathogenesis, whether directly through cardiovascular mediation or indirectly through affecting cardiovascular risk factors.

Fig. 2.

Mechanistic Links Between B-Vitamins and Cardiovascular Disease. Integrated schematic illustrating four principal mechanisms through which B-vitamins influence cardiovascular health: (1) homocysteine metabolism (B6, B9, B12) (2), DNA methylation and epigenetic regulation (B9, B12) (3), modulation of oxidative stress and inflammation (B2, B3, B6), and (4) maintenance of lipid and energy metabolism (B1, B3, B5)

The principal mechanistic pathways through which B vitamins influence cardiovascular outcomes are summarized in (Table 2).

Table 2.

Overview of mechanistic pathways linking B vitamins to cardiovascular outcomes, with population and trial evidence. References as in text

Homocysteine metabolism (77–86, 131–144)	B6, B9, B12	Remethylation & transsulfuration; ↓ homocysteine	Endothelial protection, ↓ stroke incidence	Elderly, CKD, folate-deficient populations	HOPE-2, CSPPT, VISP; meta-analyses confirm ↓ homocysteine, mixed outcomes
Epigenetic regulation (87–90)	B9, B12, B6	DNA methylation via one-carbon metabolism	Vascular remodeling, aneurysm risk	CAD, AAA cohorts	EPICOR & case-control studies: altered methylation with low intake
Oxidative stress & inflammation (23, 91–95)	B2, B3, B6	Antioxidant pathways (Nrf2, SOD), NF-κB inhibition	Reduced ROS, ↓ arterial stiffness, improved HF outcomes	Diabetic, hypertensive, metabolic syndrome populations	RIBOGUT, AIM-HIGH, animal models
Lipid & energy metabolism (96–102)	B1, B3, B5	ATP production, lipid oxidation, NAD+ metabolism	Improved contractility, atheroprotection (historical); mixed in statin era	HF, MI patients; metabolic cohorts	ARBITER, HATS, AIM-HIGH, VITACOG
Special populations (113–162)	All B vitamins	Nutrient absorption, homocysteine clearance, energy pathways	Elderly: ↑ CVD risk with deficiencies; pregnancy: ↑ CHD risk in offspring	Elders, vegans, bariatric, CKD, pregnancy	HOST, DIVINe, FAVORIT, observational pregnancy cohorts
Precision nutrition & genetics (183–195)	B2, B9, B12	Genotype-guided supplementation (MTHFR, TCN2)	Targeted BP reduction, ↓ stroke risk	MTHFR TT carriers; genetic risk groups	Mendelian randomization & nutrigenetic RCTs

Homocysteine pathway

Homocysteine is a non-essential sulfur-containing amino acid generated as an intermediate in methionine metabolism, which ultimately contributes to glutathione synthesis [88]. The processes of remethylation and transsulfuration of homocysteine are both dependent on B vitamins 6, 9, and 12.

In remethylation, homocysteine is converted back to methionine and requires the aid of folate and vitamin B12 as cofactors [89]. Meanwhile, in transsulfuration, homocysteine is irreversibly converted to cysteine using two enzymes, both of which require vitamin B6 as a cofactor [90]. Inadequate levels of B vitamins have been linked to impaired homocysteine clearance, resulting in elevated plasma homocysteine levels, also known as hyperhomocysteinemia [91]. Hyperhomocysteinemia is linked to endothelial dysfunction, oxidative stress, and prothrombotic effects, all of which subsequently worsen CVDs [92].

Among the proposed mechanisms, disruption of homocysteine metabolism represents one of the most direct and well-established links between B-vitamin deficiency and cardiovascular pathology. At the molecular level, elevated homocysteine induces endothelial dysfunction through multiple B-vitamin–dependent pathways. Homocysteine promotes oxidation of tetrahydrobiopterin (BH4), leading to endothelial nitric oxide synthase (eNOS) uncoupling and a shift from nitric oxide to superoxide production, thereby impairing vasodilation. This process is particularly sensitive to folate availability, as 5-methyltetrahydrofolate (5-MTHF) stabilizes BH4 and supports eNOS coupling [93, 94]. In parallel, homocysteine increases intracellular levels of asymmetric dimethylarginine (ADMA) by inhibiting dimethylarginine dimethylaminohydrolase (DDAH), resulting in competitive inhibition of eNOS and further reduction in nitric oxide bioavailability. Vitamin B₆ deficiency further exacerbates vascular injury by impairing cystathionine β-synthase (CBS) activity in the transsulfuration pathway, reducing cysteine and glutathione synthesis. This leads to depletion of reduced glutathione (GSH), accumulation of reactive oxygen species, and activation of redox-sensitive pathways such as NF-κB, promoting endothelial inflammation and expression of adhesion molecules including VCAM-1 and ICAM-1 [95, 96].

Litvinov et al.’s study shows how hyperhomocysteinemia directly modulates platelet function and blood clot contraction [97]. When homocysteine was moderately increased, this enhanced platelet-driven contraction, but with time, it led to impaired contractility and platelet exhaustion, causing larger unstable clots to be formed. Wu et al.’s study suggests a mechanism in which homocysteine disrupts endothelial redox homeostasis by inducing oxidative stress of the endoplasmic reticulum [98]. This was demonstrated in their experiment, as mouse models with hyperhomocysteinemia showed an upregulation of endoplasmic reticulum oxidase called Ero1α, and elevated levels of ICAM-1 and VCAM-1. Wu et al.’s cell cultures also demonstrated over-oxidation and redox imbalance when treated with homocysteine, showing how oxidative stress can be linked to homocysteine levels [98].

In Wang et al.’s animal study, homocysteine was shown to aggravate myocardial ischemia-reperfusion injury, as shown by using rat models and treating them with homocysteine. Results demonstrated mitochondrial dysfunction, excessive ROS production, and the activation of the ERK1/2 signaling cascade. When the ERK1/2 signaling cascade was inhibited, cardiac dysfunction was reduced, suggesting that homocysteine promotes oxidative stress through that pathway [99].

The management of hyperhomocysteinemia can be managed through the supplementation of B vitamins, as they are important regulators of homocysteine metabolism. In Maruyama et al.’s randomized controlled trial, low-dose supplementation with folate, B6, and B12 significantly reduced homocysteine levels in Japanese adults with metabolic syndrome [100]. Zamani et al.’s meta-analysis further supports this, as 21 different randomized trials were used, and their analysis showed that folic acid supplementation improved endothelial function significantly, as reflected by improved flow-mediated dilation [71]. Clarke et al.’s meta-analysis supported that as well. Their meta-analysis, involving over 22,000 individuals, demonstrated that B vitamin supplementation reduced homocysteine concentrations by 25 to 30% [101] (Fig. 3).

Fig. 3.

Homocysteine Pathway and B-Vitamin Regulation. The methionine–homocysteine cycle and its dependence on B-vitamins. Folate (B9) and cobalamin (B12) act as cofactors in the remethylation of homocysteine back to methionine, while pyridoxine (B6) is required for transsulfuration of homocysteine to cysteine. Deficiencies in these vitamins impair clearance and lead to hyperhomocysteinemia, which promotes endothelial dysfunction, oxidative stress, and thrombosis, thereby contributing to cardiovascular disease

Methylation and epigenetic regulation

Despite DNA methylation being a systemic regulatory process, its cardiovascular relevance arises when these modifications affect vascular-specific genes involved in endothelial function, inflammation, and atherogenesis. B vitamins 9 and 12 play a central role in one-carbon metabolism, which is necessary for methyl-group donation in the DNA methylation process. DNA methylation is an epigenetic process in which gene expression is altered without affecting the DNA sequence itself. Folate is converted to methyl-tetrahydrofolate, which donates a methyl group to homocysteine in the remethylation cycle, producing methionine [102]. Vitamin B12 is required as a cofactor in this cycle, and vitamin B6 indirectly influences methylation through its role in the transsulfuration pathway [90]. Deficiencies in folate or B12 could disrupt this process, thus altering methylation patterns and vascular gene regulation.

Disruption of folate- and vitamin B₁₂–dependent one-carbon metabolism reduces S-adenosylmethionine availability, leading to altered DNA methylation of vascular genes such as MCP-1 and eNOS, thereby promoting endothelial inflammation and atherogenesis.

Evidence suggests that altered DNA methylation is associated with cardiovascular pathology [103]. Sharma et al. investigated through a case-control study how individuals with confirmed coronary artery disease had significantly higher global DNA methylation in comparison with the healthy controls. Vats et al. also demonstrated through a cohort study how abdominal aortic aneurysms had higher DNA methylation than the age-matched controls, and that there was a correlation between baseline aortic diameter and DNA methylation, demonstrating how epigenetic dysregulation contributes to aneurysm initiation and vascular wall remodeling [104].

The effect of B vitamins on methylation patterns has been confirmed in various studies. In the EPICOR study, Fiorito et al. detected methylation at genes involved in one-carbon metabolism and homocysteine pathways, and they were able to identify more methylated regions in individuals with MI than in the controls. Their study also demonstrated that lower B-vitamin intake was associated with unfavorable methylation profiles, suggesting a link between dietary B vitamins and epigenetics [105]. Findings suggest that the cardiovascular impact of B-vitamins on methylation is context-dependent and may reflect both direct vascular gene regulation and broader systemic epigenetic effects.

Oxidative stress and inflammation

Oxidative stress and inflammation are central processes in the progression of cardiovascular diseases, and several B vitamins have a role in their regulation. Riboflavin and niacin influence oxidative stress through defined molecular pathways, including FAD-dependent glutathione reductase activity and NAD⁺-dependent SIRT1 signaling, which regulate Nrf2-mediated antioxidant responses and suppress NF-κB–driven vascular inflammation. Regarding riboflavin, the RIBOGUT trial conducted by Bourgonje et al. involved healthy volunteers who were given riboflavin supplements for two weeks, and any alterations recorded in serum free thiols were then used as markers of oxidative stress [106]. Changes in albumin-adjusted free thiol levels were inversely associated with changes in C-reactive protein (CRP), suggesting riboflavin may influence inflammatory balance in healthy individuals. Xu et al. demonstrated, using a murine transverse aortic constriction heart failure model, how riboflavin supplementation improved cardiac function and reduced oxidative stress [28]. In Xu et al.’s experiment, riboflavin activated short-chain acyl-CoA dehydrogenase and upregulated the DJ-1–Keap1–Nrf2 signaling pathway, which reduces myocardial fibrosis and apoptosis.

Niacin has also been investigated for its anti-inflammatory potential. In a systematic review and meta-analysis of 15 randomized controlled trials, Rad et al. demonstrated how niacin supplementation is associated with reductions in CRP and TNF-α and increased levels of adiponectin and leptin [107]. Additionally, in an NHANES cohort study involving CVD patients, individuals with the highest dietary niacin intake had the lowest CVD and all-cause mortality [108].

Pyridoxine has shown similar effects on oxidative stress and inflammation. In an experimental study of diabetic cardiomyopathy, Mutavdzin Krneta et al. treated streptozotocin-induced diabetic rats with pyridoxine for 28 days and observed significant improvements in cardiac oxidative stress parameters [109]. It was observed that cardiometabolic disturbances were reduced, and lactate, malate dehydrogenase, and catalase levels were all shifted toward a profile consistent with improved mitochondrial metabolism, demonstrating how pyridoxine counters dysfunction in the diabetic heart. Studies with human subjects, such as the Boston Puerto Rican Healthy Study by Shen et al., report similar evidence [110]. The higher the pyridoxine levels were, the lower the concentration of CRP, homocysteine, and oxidative DNA damage. Evidence from both experimental and clinical studies highlights the important role of riboflavin, niacin, and pyridoxine in oxidative stress & inflammation, and subsequently cardiac health.

Some of these antioxidant and anti-inflammatory effects may reflect generalized improvements in cellular redox status rather than direct targeting of vascular tissues, which may contribute to the inconsistency observed in clinical outcomes.

Lipid and energy metabolism

Energy production and lipid balance are critical for cardiovascular health. The heart requires a continuous supply of ATP, and any disturbances in mitochondrial energy generation could affect contractility, pump function, and eventually lead to heart failure [111]. Thiamine functions as a coenzyme in carbohydrate metabolism and ATP synthesis, making it essential in cardiovascular health. Thiamine deficiency has been associated with several CVDs, including MI, conduction defects, and heart failure [112]. Yamada et al. demonstrated that ischemia-reperfusion rat models that received pretreatment of thiamine pyrophosphate had preserved left ventricular contractile function and no excessive mitochondrial fission, and thus were protected against ischemic injury [113]. Vazquez et al.’s animal study demonstrated how thiamine deficiency reduced energy state in the liver, affecting ATP generation, glucose levels, and serum lactate [114]. Their results also showed metabolic and genetic changes, including modified mRNA of carbon metabolism, indicating how serious thiamine deficiency is. Clinical evidence also suggests potential benefit from thiamine supplementation, such as Yue et al.’s analysis of 1782 MI patients from a database. Their results reported that thiamine supplementation during hospitalization of MI patients reduced their in-hospital, 30-day, and 90-day mortality [115].

Regarding lipid balance and metabolism, niacin plays a significant role. In a meta-analysis of twelve RCTs, Saboori et al. found that niacin supplementation reduced apolipoprotein B levels significantly, while increasing apolipoprotein A1 [116]. These shifts highlight niacin’s ability to improve lipid transport; however, not all studies have favorable outcomes. In Ronsein et al.’s study, which analyzed samples from AIM-HIGH and CPC trials, results show that niacin therapy increased HDL-associated proteins linked to atherosclerosis, such as clusterin, which is why clinical benefit is not apparent despite HDL-C levels improving [117]. Thus, niacin has the potential to modulate lipid metabolism favorably, but its benefit is dependent on other parameters and treatment context.

This suggests that improvements in lipid profiles do not necessarily translate into direct cardiovascular benefit, particularly in the context of contemporary medical therapy. Thus, while certain B vitamins such as thiamine or niacin play an essential role in energy and lipid metabolism, most of their cardiovascular effects are due to systemic improvements and metabolic efficiency rather than direct effects on vascular structure or function. This mechanism demonstrates how B-vitamins affect cardiovascular risk factors, thus indirectly affecting cardiovascular health.

Clinical and epidemiological evidence

Clinical and epidemiological studies have provided mixed evidence regarding the benefits of B vitamins. Cross-sectional and case-control studies have provided evidence linking B vitamins to cardiovascular outcomes. Wald et al. in their meta-analysis demonstrated that individuals with lower folate and B12 had higher plasma homocysteine, which was consistently associated with a greater risk of CVD [118]. This is consistent with the mechanism of B12 and folate affecting homocysteine metabolism, and with the lack of B vitamins, homocysteine increases. Shen et al., in their case-control analysis within the Boston Puerto Rican Health study, demonstrated how pyridoxal was significantly associated with lower CRP levels and oxidative damage, suggesting B6’s effect on inflammation and cardiovascular health [110]. In Jin et al.‘s and Sowndarya et al.’s cross-sectional studies, both demonstrated how increased B-vitamin supplementation , whether riboflavin, folate, or B12, has positive effects on individuals’ health [119, 120].

Prospective cohort studies further support the evidence presented above. Zhang et al., in their analysis of over 115,000 participants in the UK biobank, demonstrated how higher folate and B6 intake is associated with lower CVD incidence and mortality [121]. Jeon and Park’s cohort also supported similar results, as higher dietary B6 was associated with significantly reduced CVD risk in men [122].

However, these observational findings should be interpreted with caution, as they are inherently susceptible to residual confounding and often lack detailed characterization of baseline nutritional status, regional dietary patterns, and fortification exposure, all of which may significantly influence cardiovascular risk estimates.

It is important to note that some populations have a higher risk of being B12-deficient, like vegetarians, thus resulting in a higher incidence of hyperhomocysteinemia and CVD. This was observed in Pawlak et al.’s study, noting that cardiovascular benefits from plant-based diets might be offset due to B12 deficiency [123]. These findings support the view that adequate dietary intake of B vitamins plays a role in CVD incidence and mortality.

RCTs, however, have provided less consistent evidence, and these discrepancies appear to be strongly influenced by differences in trial context. In the HOPE-2 trial, 5500 high-risk patients used folic acid, vitamin B6, and vitamin B12 supplements [124]. This reduced homocysteine levels by 25%, but had no significant reduction in MI, stroke, or cardiovascular death. In Ebbing et al.’s analysis of the NORVIT and WENBIT trials, they confirmed that while homocysteine was reduced, there was no significant reduction in cardiovascular events during the extended follow-up [125]. Heinz et al.’s randomized trial of ESRD patients demonstrated similar results, as supplementation lowered homocysteine levels but didn’t reduce cardiovascular events or mortality [126].

These findings highlight a key disconnect between biochemical improvements and clinical outcomes, suggesting that homocysteine reduction alone may not be sufficient to confer cardiovascular protection in all settings. Importantly, interpretation of these trials requires consideration of key contextual factors, including baseline nutritional status, regional folate fortification policies, and concurrent pharmacologic therapies. Many trials were conducted in populations with adequate baseline B-vitamin status or in regions with mandatory folate fortification, thereby limiting the potential for additional benefit. Furthermore, participants were frequently receiving contemporary evidence-based therapies, including statins and antihypertensive medications, which may have minimized any cardiovascular effect of B-vitamin supplementation. Collectively, these factors suggest that the apparent lack of benefit in RCTs may reflect study design and population characteristics rather than the absence of a true biological effect.

These studies demonstrate how, despite vitamin B influencing homocysteine, its effect on CVD and cardiovascular events as a whole is not significant. In one post hoc analysis of the VISP trial, Arshi et al. demonstrated that high-dose B vitamin therapy increased recurrent stroke risk, thus putting the efficacy of vitamin B into question [127].

Special populations and clinical contexts

The Impact of B-vitamin status on cardiovascular health differs in certain populations, especially those who have unique physiological and dietary characteristics [128] (Fig. 4).

Fig. 4.

Special Populations at Risk for B-Vitamin Deficiency. Populations with increased risk of cardiovascular complications due to inadequate B-vitamin status. Elderly individuals are predisposed to B12 and folate malabsorption, vegetarians/vegans are vulnerable to B12 deficiency, patients with chronic kidney disease exhibit impaired vitamin handling and hyperhomocysteinemia, and pregnant women with inadequate folate/B12 intake have elevated risks of congenital heart disease and adverse fetal programming

Elderly populations

Older adults are usually prone to age-related changes in diet and food absorption, which increase the risk of developing many nutritional deficiencies, such as vitamin B12 and B9 (folate) [129]. Olders adults often have atrophic gastritis, diminishing stomach acid production, which causes malabsorption of vitamin B12 and thus the risk of developing vitamin B12 deficiency [130]. Even mild or early-staged subclinical deficiencies can contribute to increased cardiovascular risk (endothelial dysfunction and arterial stiffness) as they elevate homocysteine levels and increase the risk of neurological problems [131]. In addition, older adults receiving metformin and proton pump inhibitors concurrently are at a significantly higher risk of developing vitamin B12 deficiency, as reported by Choungwon Jung et al. in a retrospective cohort study [132]. Folate deficiency is also common in elders and originates from inadequate dietary intake, medication interference (like methotrexate and anticonvulsants), alcoholism, and polypharmacy. This increases homocysteine levels, contributing to cardiovascular risks [133]. Diseases that commonly affect elders, including Alzheimer’s disease and various cancers, can lead to suboptimal vitamin B6 status [134]. This can lead to elevated levels of homocysteine and thus cardiovascular risk [135]. Wang et al. reported in their prospective cohort study that among elders with lower serum levels of pyridoxal 5’-phosphate (PLP) which is the active form of vitamin B6 are significantly at higher risk of cardiovascular and all-cause mortality and high vitamin B6 turnover (suggested by higher 4-pyridoxic acid [4-PA] over PLP ratio [4-PA/PLP ratio]) increased risk of cardiovascular mortality, cancer mortality and all cause mortality. This suggests that maintaining adequate vitamin B6 levels may be a protective factor against premature death in older adults and supports the idea of using nutritional biomarkers like PLP and 4-PA in identifying individuals at higher risk [136].

Vegetarians, vegans, and bariatric surgery patients

Vitamin B12 is primarily found in animal products, making vegetarian and vegan diets (which are low in vitamin B12) vulnerable to vitamin B12 deficiency [137]. Although these diets are usually associated with lower cardiovascular risks, inadequate vitamin B12 levels, which lead to increased homocysteine, can counter these benefits [138]. Plant-based diets are usually rich in folate, which may mask vitamin B12 deficiency, delaying its recognition while the neurologic damage keeps progressing [139]. Thus, people on such diets are advised to take proper supplementation of vitamin B12 or rely on fortified foods to ensure adequate intake and prevent irreversible neurocognitive effects or other health issues [140, 141]. However, a large population-based study done by Paula Schorgg et al. reported no significant difference in PLP or 4-PA levels between vegetarians, flexitarians, pescatarians, and meat-eaters, suggesting that vegetarian diets do not pose a risk for vitamin B6 deficiency [142]. Patients who have undergone bariatric surgery are also prone to a wide range of nutritional deficiencies, including B vitamins, due to the alteration in anatomy and malabsorption. Thus, it is important to carefully monitor and supplement this population in order to protect them against cardiovascular complications [143]. Gastric bypass (Roux-en-Y) and biliopancreatic diversion (BPD) are associated with the greatest risk of developing B vitamin deficiencies as they bypass significant portions of the gastrointestinal tract, thus impairing absorption of vitamins B12, folate, and thiamine (B1) [144]. with thiamine deficiency occurring early, mainly due to recurrent vomiting and poor intake, thus carrying a risk of developing Wernicke’s encephalopathy, peripheral neuropathy, and cardiomyopathy, highlighting the need for lifelong supplementation [145].

Patients with chronic kidney disease

Deficiency risk in CKD

Patients with chronic kidney disease (CKD) exhibit significantly altered metabolism of B vitamins, contributing to hyperhomocysteinemia, which affects up to 85% of patients [146]. Impaired renal clearance of homocysteine plays a central role, as healthy kidneys normally remove a substantial portion of circulating homocysteine [147]. In addition, the kidney is a metabolically active site for homocysteine metabolism through B-vitamin–dependent pathways, and dysfunction of these pathways further promotes its accumulation [148].

CKD patients are also at increased risk of B-vitamin deficiency due to multiple contributing factors. Reduced dietary intake secondary to protein restriction, poor appetite, nausea, and uremia-related gastrointestinal dysfunction leads to decreased intake and absorption of B vitamins [149]. Furthermore, as water-soluble vitamins, B vitamins are lost during hemodialysis, further exacerbating deficiency [150]. Vitamin B6 levels are particularly affected, as the uremic state reduces levels of its active form, pyridoxal-5′-phosphate (PLP), compounding dietary insufficiency [149].

Biomarker interpretation in CKD

Assessment of B-vitamin status in CKD is particularly challenging due to discrepancies between circulating levels and tissue availability. Although serum folate levels may appear normal, a functional deficiency may exist at the cellular level due to impaired uptake of 5-methyltetrahydrofolate in the presence of uremic toxins [151]. Vitamin B12 metabolism is similarly affected. Circulating levels may not accurately reflect tissue availability due to elevated transcobalamin levels, which impair cellular uptake [151]. Additionally, proximal tubular dysfunction contributes to urinary loss of vitamin B12, further worsening deficiency [151]. The commonly used supplemental form, cyanocobalamin, requires conversion to methylcobalamin, a process that releases small amounts of cyanide. In CKD patients, reduced renal clearance of cyanide may impair this conversion, thereby limiting the effectiveness of supplementation [151].

Supplementation evidence

Despite strong mechanistic rationale for homocysteine lowering, clinical trials evaluating B-vitamin supplementation in CKD have yielded inconsistent results. The HOST trial (2004), in which folic acid, vitamin B6, and vitamin B12 were administered to more than 2000 CKD and end-stage renal disease patients, demonstrated no reduction in all-cause mortality or cardiovascular events despite lowering homocysteine levels [152].

Similarly, the DIVINe trial (2009), which administered high-dose B vitamins (folic acid 2.5 mg, B6 25 mg, B12 1 mg) to patients with diabetic nephropathy, showed no cardiovascular benefit and reported a faster decline in kidney function along with increased cardiovascular events in the treatment group [152]. The FAVORIT trial (2011), conducted in stable kidney transplant recipients, also demonstrated no significant improvement in cardiovascular outcomes despite effective homocysteine reduction [153].

In the HOPE-2 trial (2006), B-vitamin supplementation in patients with vascular disease or diabetes, including a subset with renal dysfunction, did not significantly reduce cardiovascular events overall [154]. However, secondary analyses revealed a reduction in stroke incidence, suggesting a potential cerebrovascular benefit in selected populations [155].

Clinical recommendations

Given the high prevalence of deficiency and altered metabolism, B-vitamin supplementation may be considered as adjunctive therapy in CKD patients, particularly those undergoing dialysis or with documented deficiencies [152]. Patients on dialysis may require higher doses to compensate for continuous losses of water-soluble vitamins [150]. However, routine high-dose supplementation for cardiovascular prevention is not supported by current evidence. A targeted, individualized approach that incorporates nutritional assessment, dialysis-related losses, and careful interpretation of functional biomarkers is recommended to guide clinical management.

Pregnant women and offspring

During pregnancy, adequate B-vitamin status is essential for both maternal and fetal cardiovascular health. Folate and vitamin B12 play central roles in one-carbon metabolism, DNA synthesis, and methylation processes that influence fetal cardiovascular development [156]. Deficiency of these vitamins leads to impaired homocysteine metabolism, resulting in elevated homocysteine levels, which are associated with adverse cardiovascular and developmental outcomes [157].

Folate deficiency during early pregnancy is strongly associated with neural tube defects and congenital heart disease (CHD) in offspring [158]. Similarly, maternal vitamin B12 deficiency has been linked to increased risks of preeclampsia, gestational diabetes, and preterm birth [159–162]. Beyond structural abnormalities, inadequate maternal B-vitamin status may influence long-term cardiometabolic health in offspring through epigenetic mechanisms. Low maternal folate has been associated with higher body mass index in children, while low maternal B12 levels have been linked to higher heart rate and adverse metabolic profiles [156, 163]. In addition, maternal B12 deficiency and elevated homocysteine levels have been associated with altered neuroendocrine stress responses in offspring, including increased cortisol and heart rate responses to stress [164]. Large-scale studies demonstrate that periconceptional folic acid supplementation reduces the risk of congenital heart defects by up to 50% [158]. Low maternal folate levels increase the risk of CHD up to threefold, and when combined with elevated homocysteine, the risk may increase up to ninefold [158]. However, excessive folate intake in the presence of vitamin B12 deficiency may mask hematologic manifestations of B12 deficiency, allowing neurological damage to progress undetected [165]. Moreover, maternal folate levels demonstrate a U-shaped association with CHD risk, with both low and high levels associated with increased risk [158]. Vitamin B6 may also contribute to pregnancy outcomes. Low levels of pyridoxal-5′-phosphate (PLP) have been associated with elevated homocysteine, placental dysfunction, and adverse pregnancy outcomes, although further research is needed to clarify its direct role in fetal cardiovascular programming [166].

Overall, maintaining balanced and adequate levels of folate, vitamin B12, and potentially vitamin B6 is essential not only for preventing congenital cardiovascular abnormalities but also for supporting long-term cardiovascular and metabolic health in offspring.

Therapeutic and preventive implications

Managing B-vitamin status is important for cardiovascular health and risk reduction; however, therapeutic and preventive strategies vary in the strength of supporting evidence. Established clinical practices include the treatment of documented deficiencies and population-based fortification programs. In contrast, other approaches, such as combination therapy and homocysteine lowering strategies for cardiovascular prevention, remain areas of ongoing investigation with inconsistent clinical outcomes. Emerging fields, including precision nutrition and genotype guided supplementation, represent promising but not yet fully established strategies. Therefore, clinical application requires careful interpretation of the current evidence base.

Screening and diagnosis

Accurate detection of B vitamin deficiency is crucial to reducing cardiovascular risks and preventing complications. Diagnosing B vitamin deficiency can be challenging, especially for vitamin B12. Serum vitamin concentration is the traditionally used diagnostic approach although it may not always reflect the functional availability at cellular level such as vitamins B12 levels appearing normal in presence of functional deficiency particularly in elderly or CKD patients [167]. This occurs due to the binding of B12 with an inactive transport protein (haptocorrin) not being distinguished from the biologically active form, holotranscobalamin (holoTC) in serum levels test [168]. Functional biomarkers like plasma homocysteine and methylmalonic acid (MMA) can be a more sensitive indicator of impaired one-carbon metabolism and intracellular vitamin status. MMA is considered highly specific for B12 deficiency as it rises when there are insufficient amounts of B12 for the methylmalonyl-CoA mutase enzyme to function properly. Homocysteine is highly sensitive to B12 deficiency but less specific than MMA, as it rises with folate and B6 deficiencies or renal impairment. If both MMA and homocysteine levels are elevated, this is highly suggestive of B12 deficiency even if serum levels are normal [169]. Thus, relying on serum B12 level solely to diagnose B12 deficiency can lead to underdiagnosis. Some emerging biomarkers may improve diagnostic accuracy. Holotranscobalamin (holoTC), the biologically active fraction of vitamin B12 bound to transcobalamin, is a more reliable early marker of deficiency as it reflects the portion available for cellular uptake [170, 171]. Similarly, vitamin B6 status can be better evaluated using the ratio of 4-PA to PLP, as elevated 4-PA/PLP ratios indicate increased vitamin B6 turnover and thus are associated with higher cardiovascular and all-cause mortality [172]. Population-specific considerations are also essential. South Asian populations have a higher prevalence of B12 deficiency and hyperhomocysteinemia despite apparently adequate intake, , suggesting that population-specific diagnostic thresholds may be needed, which may need to tailor the diagnostic cutoffs for south asians [173, 174]. Thus, personalized screening strategies may allow earlier intervention and risk-reduction in higher-risk groups. Also, older adults with age-related atrophic gastritis need higher cutoffs, as low-normal B12 levels can manifest with neurological symptoms. There is also a need for pregnancy-specific reference ranges to avoid the maternal and fetal risks and accurately identify deficiencies, and guide supplementation [175]. In clinical practice, integrating both serum and functional biomarkers with population-specific thresholds may provide the most reliable approach for early detection and reducing risks, although it may not always be feasible due to cost, availability, and resource limitations.

Supplementation and fortification

Supplementation and fortification of B vitamins are recommended, especially in high-risk groups. B12 supplementation can be oral or parenteral. Oral B12 (> 1000 µg/day) is as effective as intramuscular in correcting deficiency for most individuals, including elderly or mild malabsorption patients [176]. However, in severe malabsorption patients (pernicious anemia, Post-bariatric surgery), parenteral replacement is the route of choice [177]. Folate fortification programs have been shown to achieve a significant reduction in neural tube defects worldwide, in addition to a possible drop in stroke risk by lowering homocysteine levels in the general population worldwide [178, 179]. Chia-Yu Hsu et al. in a meta-analysis of randomized controlled trials confirmed that mandatory folate fortification with or without minimal cyanocobalamin, particularly in countries without prior supplementation policies, was associated with reduced stroke mortality [180]. However, excessive folate intake in the presence of an undetected B12 deficiency, masking it, might allow neurological damage to progress. Also, some observational studies have linked high folate with low B12 status to an increased risk of certain cancers, though causality remains uncertain [181]. Thus, supplementation and fortification strategies should ensure adequate intake of both folate and B12 to avoid potential harm. Niacin supplementation has been used historically to treat dyslipidemia by increasing HDL and lowering triglycerides. However, recent studies have suggested limited benefit when niacin is added to statin therapy, thus shifting its role to patients with specific lipid disorders or statin intolerance. Also, recent randomized controlled studies (AIM-HIGH, HPS2-THRIVE) showed no benefit of decreasing cardiovascular risks with increased adverse effects like flushing, hepatotoxicity, insulin resistance, and gout [182, 183].

Combination therapy

The supplementation of all three vitamins B6, B9, and B12 has been shown to lower homocysteine levels more efficiently than single-agent therapy, as one-carbon metabolism depends on them [184]. However, although biochemical improvements occur, their clinical cardiovascular effects remain debated. Current evidence does acknowledge the stroke-reduction benefits, especially in deficient populations (like the China Stroke Primary Prevention Trial [CSPPT], HOPE-2) [124, 185], but Western guidelines [ACC/AHA, ESC] still discourage routine B-vitamins supplementation as a universal cardiovascular prevention strategy [186].

Precision nutrition and genetic considerations

Vitamin B2 (riboflavin) is an important cofactor for one-carbon metabolism by the MTHFR enzyme [187].Individuals MTHFR 677TT genotype have impaired enzyme activity, causing impaired folate metabolism, higher homocysteine levels and, consequently, increased cardiovascular risks [188]. Emerging evidence demonstrates that riboflavin supplementation in such individuals lowers blood pressure significantly and improves vascular outcomes in this population [184]. These findings highlight the potential role of genotype-guided B-vitamin therapy as a personalized strategy for cardiovascular prevention, though further large-scale trials are needed before widespread clinical adoption.

Lifestyle and dietary approaches

For the general population, relying on whole-food sources that are rich in B vitamins remains the preferred preventive approach over pharmacological supplementation. Dietary patterns rich in folate (leafy green vegetables), B12 (dairy and animal products), B6 (whole grains), and legumes are associated with reduced cardiovascular risks and improved outcomes [190]. On top of this, whole food sources do provide other cardioprotective contents like fibers, antioxidants, and polyphenols [191, 192]. Public health strategies must be balanced based on communities, as low-resource settings must have fortification plans for the general population while high-resource settings must focus on individualized supplementation focusing on high-risk groups (elderly, vegans, bariatric patients, CKD patients, pregnant women), thus enhancing cardiovascular and other general health outcomes.

Researchers combining nutrition science with genetics and personalized medicine could identify which populations benefit the most from B vitamin supplementation or interventions, making cardiovascular prevention strategies more effective, although they may not always be feasible.

In the future, integrating nutrition science with genetics and personalized medicine may help identify populations most likely to benefit from B vitamin-based interventions, improving cardiovascular prevention strategies. However, implementation of these strategies may be limited by cost, accessibility, and variability in healthcare resources.

Knowledge gaps and future directions

A major gap in current research is the lack of standardized and functionally relevant biomarkers for assessing B-vitamin status. Emerging evidence suggests that functional markers such as methylmalonic acid (MMA) may better predict cardiovascular outcomes than serum B12 alone, as demonstrated by Guo et al., who showed that MMA more accurately predicts cardiovascular mortality in patients with coronary heart disease [193]. Similarly, a recent scoping review highlighted that holotranscobalamin (holo-TC), representing the biologically active fraction of B12, provides a more accurate assessment of vitamin status and should be incorporated alongside MMA in both research and clinical practice [194]. These findings underscore the need for standardized multi-marker approaches to improve diagnostic accuracy and risk stratification. Another important gap lies in interindividual variability in response to B-vitamin supplementation. Genetic polymorphisms in one-carbon metabolism pathways, particularly involving MTHFR and TCN2, play a significant role in modulating both biomarker levels and clinical outcomes. Cheng et al. identified key genetic determinants influencing one-carbon biomarkers, reinforcing the value of integrated biomarker panels [195]. Additionally, variants such as TCN2 776 C > G have been associated with altered B12 handling and increased cardiometabolic risk [196]. Evidence from Fezeu et al. further demonstrates that individuals carrying the MTHFR 677TT genotype exhibit greater reductions in homocysteine when treated with higher doses of B vitamins, suggesting that genotype-informed supplementation strategies may enhance therapeutic efficacy [197].

There remains a notable discrepancy between the lack of benefit observed in composite cardiovascular outcomes and the more consistent findings in cerebrovascular disease. Kataria et al., in a meta-analysis of patients with prior stroke or transient ischemic attack, demonstrated that B-vitamin therapy reduces recurrent stroke and vascular mortality [198]. Supporting this, Mendelian randomization analyses by Yuan et al. suggest a causal relationship between homocysteine levels and specific stroke subtypes, including ischemic and subarachnoid stroke [199]. These findings highlight the need to focus on stroke-specific outcomes rather than broad cardiovascular endpoints when evaluating B-vitamin interventions. A further limitation of existing clinical trials is the inclusion of heterogeneous populations without accounting for baseline nutritional status. The CSPPT trial by Huo et al. demonstrated that folic acid supplementation significantly reduced first stroke incidence in a population characterized by low folate levels and elevated homocysteine [200]. These findings suggest that targeting individuals with documented deficiencies may reveal clinically meaningful benefits. Accordingly, recent recommendations emphasize the importance of prospective screening using functional biomarkers such as MMA and holo-TC, as well as focusing on long-term cerebrovascular outcomes to avoid dilution of treatment effects in low-risk populations (Fig. 5).

Fig. 5.

Future Directions in Precision Nutrition. Proposed framework for personalized B-vitamin therapy in cardiovascular prevention. Integration of genetic testing, biomarker assessment (MMA, holo-TC, homocysteine), and targeted supplementation may optimize risk reduction. Future randomized trials in high-risk subgroups are required to clarify benefits, particularly for stroke prevention and endothelial protection

Conclusion

B vitamins, particularly B12, folate, and B6, play important roles in cardiovascular biology through their involvement in homocysteine metabolism, vascular function, and cellular energy processes. Observational studies consistently associate low levels of these vitamins with increased cardiovascular risk; however, major randomized trials such as HOPE-2 and NORVIT have not demonstrated a clear reduction in major cardiovascular events despite homocysteine lowering, highlighting a discrepancy between observational and interventional evidence. Emerging data from functional biomarkers, including holotranscobalamin and methylmalonic acid, as well as genetic insights involving MTHFR and TCN2 polymorphisms, suggest that cardiovascular effects may be population-specific. For example, benefits observed in the CSPPT trial and evidence from Mendelian randomization studies indicate a potential role in stroke-related outcomes and in individuals with underlying deficiencies or genetic susceptibility. Overall, current evidence does not support routine B-vitamin supplementation for universal cardiovascular prevention. Instead, a more targeted approach may be warranted in selected populations. Further research, particularly well-designed randomized trials focusing on these subgroups, is needed to clarify clinical benefit and guide implementation.

Abbreviations

CVD

Cardiovascular disease

HF

Heart failure

MI

Myocardial infarction

CKD

Chronic kidney disease

NO

Nitric oxide

eNOS

Endothelial nitric oxide synthase

PLP

Pyridoxal-5′-phosphate

MMA

Methylmalonic acid

FMD

Flow-mediated dilation

RCT

Randomized controlled trial

MTHFR

Methylenetetrahydrofolate reductase

Author contributions

AA designed and supervised the review, coordinated all authors, and finalized the manuscript. MA and KI performed the main literature search and drafted the core sections. DS and SA contributed the special-population and diagnostic-biomarker sections. BA wrote the supplementation and therapy parts and assisted with tables. SS drafted the vitamin-specific content. AE provided cardiovascular expertise and revised key mechanisms. AZ contributed to the genetics and precision-nutrition sections. ME offered senior guidance and refined the clinical interpretation AS and M.B.O reviewed epidemiological data and helped polish the manuscript. All authors approved the final version.

Funding

No funding was received for conducting this study.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.