L-citrulline as a nitric oxide–modulating therapeutic adjunct to exercise: effects on vascular function, arterial stiffness, and cardiometabolic health in postmenopausal and older women

Abstract

Postmenopausal women face increased risks of vascular dysfunction, loss of lean muscle mass, and reduced physical performance due to age-related hormonal and metabolic changes. These factors contribute to heightened cardiovascular risk and physical frailty. L-citrulline, a non-essential amino acid and precursor to nitric oxide (NO), has emerged as a potential therapeutic agent for improving vascular and muscular health. When combined with structured exercise, L-citrulline may enhance NO bioavailability, improve endothelial function, increase muscle perfusion, and potentiate exercise-induced adaptations. This review synthesizes current evidence on the combined impact of L-citrulline supplementation and exercise on endothelial function, arterial stiffness, leg muscle function, lean mass, and strength in postmenopausal women. Findings from preclinical and clinical studies suggest that this combined intervention can reduce arterial stiffness, enhance leg muscle strength, increase lean body mass, and improve overall physical function, potentially via NO-mediated vasodilation, the mechanistic target of rapamycin signaling, improved mitochondrial function, and reduced oxidative stress. These effects are especially relevant in postmenopausal populations at risk for cardiovascular disease and sarcopenia. While early results are promising, further high-quality randomized controlled trials are needed to confirm these benefits, establish optimal dosing strategies, and determine long-term clinical relevance.

Introduction

Menopause is the permanent cessation of menstrual cycles, typically occurring around 45–55 years of age, marking the end of a woman’s reproductive period. Menopause represents a major biological transition in women’s health, characterized by profound hormonal, vascular, and musculoskeletal alterations that extend well beyond reproductive aging (Kaur 2023). The decline in estrogen availability during the postmenopausal period is accompanied by widespread physiological changes that collectively increase cardiometabolic risk, impair physical function, and reduce quality of life. These changes include endothelial dysfunction, reduced nitric oxide (NO) bioavailability, increased arterial stiffness, loss of skeletal muscle mass and strength, and unfavorable shifts in body composition (Cauley 2012, Albu et al. 2013). These alterations interact across multiple biological systems, amplifying vulnerability to hypertension, frailty, mobility limitation, and cardiovascular disease (Regitz-Zagrosek 2003). From a vascular perspective, postmenopausal women frequently exhibit impaired endothelial-dependent vasodilation and increased central arterial stiffness, both of which contribute to exaggerated blood pressure responses during daily physical activity (Moreau and Hildreth 2014). Reduced NO production, driven by diminished estrogen signaling and age-related endothelial dysfunction, plays a central role in these changes. As NO is a key regulator of vascular tone, blood flow distribution, and arterial compliance, its deficiency compromises the capacity of the cardiovascular system to adapt to physical stress. These impairments not only elevate long-term cardiovascular risk but may also limit exercise tolerance and safety in older women (Donato et al. 2009, Lauer et al. 2008).

In parallel, menopause is associated with progressive declines in skeletal muscle mass, strength, and neuromuscular function. Sarcopenia and dynapenia develop through a combination of hormonal changes, reduced anabolic signaling, impaired muscle perfusion, and physical inactivity (Rolland et al. 2008, Willoughby et al. 2024). Vascular dysfunction and muscle decline are interdependent; adequate muscle perfusion and oxygen delivery are essential for maintaining muscle metabolism, contractile performance, and adaptive responses to exercise, linking vascular health directly to musculoskeletal aging (Assar et al. 2022, Prior et al. 2004). Exercise training remains the cornerstone non-pharmacological intervention to mitigate many of these menopause-related changes. Regular physical activity improves endothelial function, reduces arterial stiffness, preserves muscle mass, and enhances functional capacity (Kurbonboyev and Kaygisiz 2019). In populations with hypertension, obesity, or advanced vascular dysfunction, exercise alone may not fully restore NO signaling, vascular compliance, or anabolic sensitivity, indicating the need for adjunctive strategies to enhance physiological adaptability (Turky et al. 2013). Within this context, increasing attention has been directed toward nutritional interventions that may potentiate exercise-induced benefits. Among these, L-citrulline has emerged as a promising candidate due to its unique role in NO metabolism and vascular regulation. Unlike L-arginine, which is subject to extensive hepatic metabolism, L-citrulline is efficiently converted to L-arginine via the urea cycle, leading to sustained increases in systemic arginine availability and NO production (Moinard et al. 2008, Allerton et al. 2018). This conversion positions L-citrulline as an effective modulator of endothelial function, blood flow, and exercise-induced hemodynamic responses (Morita et al. 2013).

Beyond vascular effects, L-citrulline may influence skeletal muscle adaptations through indirect mechanisms. Enhanced muscle perfusion can improve nutrient delivery, oxygen availability, and waste removal during exercise, potentially supporting anabolic signaling and neuromuscular performance. Experimental and clinical evidence also suggests interactions between NO signaling and pathways involved in muscle protein synthesis, mitochondrial function, and neuromuscular plasticity (Allerton et al. 2018, Tengan et al. 2012). These mechanisms are particularly relevant in postmenopausal women, in whom hormonal and vascular constraints may limit the effectiveness of exercise-induced adaptations (Mercuro et al. 2007). Despite growing interest in L-citrulline, the existing literature remains fragmented. Many studies have examined L-citrulline supplementation or exercise training in isolation, often in mixed-sex or younger populations, making it difficult to extrapolate findings to postmenopausal women. Moreover, the interaction between exercise modality, supplementation strategy, and underlying physiological status has not been comprehensively synthesized (Figueroa et al. 2010, Stanelle et al. 2020, Harnden et al. 2023, Luo et al. 2025). Therefore, it remains unclear under which conditions L-citrulline may complement exercise to improve vascular health, muscle function, and physical performance in postmenopausal women. Importantly, the novelty of the emerging research lies not in positioning L-citrulline as a standalone therapeutic agent, but rather in exploring its role as a modulator of exercise responsiveness, targeting shared vascular, muscular, and metabolic pathways rather than individual outcomes. This integrative perspective aligns with contemporary models of lifestyle-based interventions. Therefore, the aim of this narrative review is to synthesize and critically evaluate current clinical evidence examining the combined effects of L-citrulline supplementation and exercise in postmenopausal and older women. Rather than focusing on isolated outcomes, this review integrates findings across vascular function, arterial stiffness, muscle mass and strength, functional performance, and molecular adaptations. By contextualizing these results within the broader pathophysiology of menopause, this review seeks to clarify the biological rationale, identify consistent patterns of response, and highlight areas where further research is needed to inform clinical and lifestyle-based strategies.

Methods

This narrative review selectively highlights studies on L-citrulline supplementation combined with exercise in postmenopausal and older women. Studies were chosen based on relevance, scientific quality, and novelty, focusing on clinical and mechanistic evidence related to vascular function, arterial stiffness, and muscle outcomes. A targeted literature search was conducted in PubMed, Scopus, and Web of Science using combinations of keywords such as “L-citrulline,” “exercise,” “postmenopausal women,” “vascular function,” “arterial stiffness,” and “muscle strength.” Articles published in English up to March 2026 were considered. While this review does not represent a systematic search, all selected studies were screened at the title, abstract, and full-text levels, and conflicting or neutral findings were explicitly reported in the Results and Discussion sections to ensure a balanced interpretation. This approach aims to provide a comprehensive and transparent synthesis of current evidence.

Pathophysiological landscape of postmenopausal aging: vascular, muscular, and molecular interactions

Menopause constitutes a major biological transition that initiates a cascade of systemic physiological changes extending far beyond the cessation of reproductive function. The progressive decline in ovarian estrogen production acts as a central trigger for alterations across vascular, muscular, skeletal, and metabolic systems, collectively shaping the health trajectory of postmenopausal women (Burger 1996). These changes interact dynamically, amplifying cardiometabolic vulnerability and accelerating functional decline with advancing age (Cabral et al. 2021). One of the most prominent consequences of estrogen withdrawal is the deterioration of vascular health. Under premenopausal conditions, estrogen supports endothelial homeostasis through multiple mechanisms, including stimulation of endothelial NO synthase activity, preservation of arterial elasticity, and suppression of pro-inflammatory signaling within the vascular wall (Mendelsohn and Karas 2005). Following menopause, the loss of these protective effects contributes to endothelial dysfunction, characterized by impaired vasodilatory capacity and reduced sensitivity to hemodynamic stimuli such as shear stress. Over time, these functional impairments are accompanied by structural remodeling of large elastic arteries, resulting in increased arterial stiffness and altered pressure wave dynamics (Kang et al. 2022, Holder et al. 2019). Epidemiological and clinical observations consistently show that postmenopausal women exhibit higher pulse wave velocity and augmentation index (AIx) compared with age-matched premenopausal women, even after accounting for chronological aging and traditional cardiovascular risk factors (Luoto et al. 2002, Kumari et al. 2008). These vascular alterations are not merely passive markers of aging but are strongly associated with elevated systolic blood pressure (SBP), increased left ventricular afterload, and heightened risk of cardiovascular events. Importantly, vascular dysfunction in this population often becomes more evident during periods of physical or sympathetic stress, when rapid vasodilation and effective pressure buffering are required. Impaired adaptability under such conditions may limit exercise tolerance and contribute to exaggerated blood pressure responses during routine physical activity, reinforcing sedentary behavior and further accelerating vascular decline (Joyner and Green 2009, Stokes et al. 2025). Concurrently, menopause is associated with accelerated deterioration of the musculoskeletal system, particularly skeletal muscle mass and strength. Although age-related muscle loss affects both sexes, women experience a disproportionate decline in muscle quality following menopause, partly driven by estrogen deficiency and its influence on muscle protein turnover, satellite cell activation, mitochondrial function, and neuromuscular integrity (Phillips and McGlory 2014, Jupil and Young-Min 2021). These changes manifest clinically as reduced strength, especially in the lower limbs, with direct consequences for mobility, balance, and fall risk. Functional impairments are often compounded by unfavorable changes in body composition, including increased fat mass and redistribution toward central adiposity, which further compromise metabolic health and physical performance (St-Onge and Gallagher 2010, Sipilä 2003). Bone health is similarly affected during the postmenopausal period. Estrogen plays a critical role in maintaining the balance between bone resorption and formation, and its decline accelerates bone loss by enhancing osteoclastic activity while suppressing osteoblastic function.

The coexistence of muscle weakness and bone loss creates a potentially compounding vulnerability, as diminished mechanical loading and impaired muscle–bone crosstalk may exacerbate skeletal fragility and fracture risk (Khosla and Monroe 2018). Together, these musculoskeletal changes contribute substantially to frailty and loss of independence in aging women. At the molecular level, reduced NO bioavailability represents a unifying mechanism linking vascular and muscular dysfunction in postmenopausal women. NO is a key signaling molecule involved in endothelial-dependent vasodilation, regulation of regional blood flow, mitochondrial efficiency, and muscle contractile function (Wu et al. 2019). Estrogen deficiency is associated with downregulation of NO synthase activity and increased oxidative stress, both of which limit NO production and accelerate its degradation. As a result, postmenopausal women often exhibit impaired vasodilatory responses and reduced capacity to match blood flow delivery with metabolic demand during physical activity (O’Donnell et al. 2007). Beyond its vascular actions, NO also interacts with anabolic and angiogenic pathways that influence capillary density, muscle remodeling, and exercise adaptability. Deficits in NO signaling may therefore contribute to blunted training responses, delayed recovery, and diminished functional gains commonly observed in older women compared with younger individuals or men. Collectively, these molecular alterations highlight the interdependence of vascular and musculoskeletal decline post-menopause and underscore the need for interventions that can simultaneously address multiple physiological targets (Aittokallio et al. 2023, Green et al. 2017). Taken together, the convergence of endothelial dysfunction, arterial stiffening, muscle weakness, bone loss, and NO deficiency establishes a complex pathophysiological environment in which traditional lifestyle interventions may yield attenuated benefits. Understanding these interrelated mechanisms provides essential context for exploring strategies designed to restore adaptive capacity. Therefore, examining the biological rationale for combining targeted nutritional approaches with exercise represents a logical next step toward identifying interventions capable of counteracting menopause-related functional and cardiovascular decline (Fig. 1).

Fig. 1.

Integrated pathophysiological changes associated with postmenopausal aging Estrogen decline after menopause initiates interconnected vascular, muscular, and skeletal alterations. Reduced nitric oxide (NO) bioavailability emerges as a central mechanism linking endothelial dysfunction, increased arterial stiffness, impaired muscle perfusion, loss of muscle strength, and bone deterioration. These interacting changes collectively contribute to reduced exercise tolerance, functional decline, and elevated cardiovascular risk in postmenopausal women

Biological basis for the synergistic effects of L-citrulline and exercise

The decline in vascular, muscular, and metabolic resilience observed after menopause reflects a convergence of endocrine disruption and impaired NO–dependent signaling. Reduced estrogen availability alters endothelial function, diminishes NO bioavailability, and compromises skeletal muscle perfusion and anabolic sensitivity (Hall 2015, Moreau et al. 2020). Exercise remains a cornerstone strategy to counteract these changes; however, its effectiveness may be attenuated by age-related impairments in vascular responsiveness and intracellular signaling efficiency (Sañudo et al. 2017). Within this framework, L-citrulline has emerged as a biologically plausible adjunct capable of enhancing exercise-induced adaptations through complementary mechanisms acting at vascular, muscular, and molecular levels (Villareal et al. 2018). L-citrulline is a non-proteinogenic amino acid primarily metabolized via the intestinal–renal axis, where it serves as a precursor for endogenous L-arginine synthesis (Maric et al. 2021). Unlike direct arginine supplementation, which is subject to extensive first-pass hepatic metabolism and gastrointestinal degradation, L-citrulline bypasses hepatic uptake and is efficiently converted to arginine in the kidneys. This pathway leads to more sustained elevations in systemic arginine availability and, consequently, enhanced substrate supply for endothelial nitric oxide synthase (eNOS)–mediated NO production (Moinard et al. 2016, Schwedhelm et al. 2008). Importantly, this mechanism is preserved with aging, suggesting that L-citrulline remains effective even in populations with compromised vascular health (Schwedhelm et al. 2008). Exercise itself is a potent physiological stimulus for NO production through increased shear stress acting on the vascular endothelium.

During both aerobic and resistance-based activities, elevations in blood flow generate mechanical forces that activate eNOS, leading to transient increases in NO release and improved vasodilatory capacity. In postmenopausal women, the endothelial response to shear stress is often blunted due to oxidative stress, reduced eNOS expression, and diminished estrogen-mediated signaling. As a result, the magnitude and duration of exercise-induced vasodilation may be insufficient to fully support muscular oxygen delivery and metabolic demand (Tinken et al. 2010, Lew et al. 2022). The combination of L-citrulline supplementation with exercise may therefore restore a more favorable vascular environment by augmenting substrate availability for NO synthesis precisely when endothelial activation is greatest (Figueroa et al. 2020). The pharmacokinetics of L-citrulline align well with exercise-induced hemodynamic demands, as plasma citrulline and arginine concentrations peak within one to two hours after ingestion and remain elevated for several hours (Rashid et al. 2020). This synchronization supports the concept that supplementation can amplify exercise-triggered NO signaling rather than acting independently. Beyond vascular effects, improved NO availability has direct implications for skeletal muscle perfusion and contractile function. NO-mediated vasodilation enhances capillary recruitment and blood flow distribution within active muscle, facilitating oxygen and nutrient delivery while promoting efficient removal of metabolic byproducts. In aging muscle, where microvascular rarefaction and endothelial dysfunction are common, these effects may be particularly relevant for maintaining exercise tolerance and supporting training adaptations (Poole et al. 2012, Landers-Ramos and Prior 2018). By improving perfusion during repeated bouts of exercise, L-citrulline may indirectly enhance the quality of mechanical loading experienced by muscle fibers. At the intracellular level, NO signaling interacts with anabolic pathways implicated in muscle protein synthesis, including the mechanistic target of rapamycin (mTOR) axis. It modulates upstream processes such as insulin sensitivity, amino acid transport, and mitochondrial efficiency, all of which influence anabolic responsiveness.

Exercise-induced activation of mTOR signaling is known to be attenuated with aging, a phenomenon often referred to as anabolic resistance. By improving vascular delivery of amino acids and enhancing metabolic signaling, L-citrulline may help overcome some components of this resistance when combined with exercise (Breen and Phillips 2011, Plénier et al. 2017). Oxidative stress represents another critical interface where exercise and L-citrulline may potentially interact, complementing each other’s effects. Menopause is associated with increased reactive oxygen species production and reduced antioxidant capacity, contributing to NO degradation and endothelial dysfunction (Braga et al. 2015). While acute exercise transiently increases oxidative stress, regular training induces adaptive upregulation of endogenous antioxidant systems. L-citrulline–derived NO may further contribute to redox balance by improving mitochondrial efficiency and reducing excessive superoxide formation, thereby preserving NO bioavailability during repeated exercise exposure (Dawoud and Malinski 2020). Taken together, these mechanisms support a complementary rather than redundant interaction between L-citrulline supplementation and exercise. Exercise introduces the physiological stimulus necessary to activate endothelial, muscular, and metabolic pathways, while L-citrulline enhances the biochemical environment required for these pathways to operate effectively (Padilla et al. 2011, El-Kirsh et al. 2011). This synergy is especially relevant in postmenopausal women, in whom impaired NO signaling and reduced anabolic sensitivity may blunt exercise adaptations. Within this framework, L-citrulline is best conceptualized as an exercise-response modulator that enhances endogenous adaptive pathways, providing a mechanistic basis for the clinical evidence discussed in subsequent sections (Fig. 2).

Fig. 2.

Proposed synergistic mechanisms of L-citrulline supplementation and exercise in postmenopausal women. Exercise-induced shear stress and muscle contraction stimulate nitric oxide–dependent signaling, while L-citrulline increases arginine availability to support sustained NO production. Together, these complementary pathways enhance endothelial function, muscle perfusion, and intracellular adaptive signaling, leading to improvements in vascular function, muscle mass and strength, and overall physical performance

Clinical trials on L-Citrulline combined with exercise and endothelial function

The body of clinical research exploring the interaction between L-citrulline supplementation and exercise in postmenopausal and older women is methodologically diverse but unified by a shared physiological rationale. As outlined in Table 1, the included trials differ with respect to intervention length, type of exercise stimulus, dosing approach, and selected endpoints, spanning from acute exercise hemodynamic responses to long-term adaptations in vascular function, muscle performance, and biochemical signaling. Given this heterogeneity, synthesizing the evidence based solely on study design would provide limited insight. Instead, the following section organizes the findings according to dominant outcome domains. Accordingly, the clinical data are discussed across four interrelated themes: peripheral and central hemodynamic responses during exercise, endothelial function and arterial stiffness, adaptations in muscle mass and functional performance, and associated molecular and neurovascular mechanisms. This framework enables a more integrated interpretation of how L-citrulline may influence exercise responsiveness across multiple physiological systems relevant to postmenopausal aging.

Table 1.

Summary of clinical trials on L-citrulline supplementation combined with exercise in postmenopausal and older women

Population (n)	Intervention & Duration	Modality	Intensity/Load	Frequency/Duration	Outcomes measured	Results	Critical notes/Limitations	Ref
22 hypertensive postmenopausal women	CIT 10 g/day vs. placebo, 4 weeks	Handgrip exercise	Submaximal isometric	Single session assessment during exercise; 4-week supplementation	Resting BP, FMD, forearm BF, VC, TSI & HHb	FMD ↑, Aortic SBP ↓, Exercise BF ↑, VC ↑, TSI ↑, HHb ↓	Small sample; mechanistic interpretation based on associative biomarkers; exploratory, hypothesis-generating	(Kang et al. 2024)
24 hypertensive postmenopausal women (CIT n = 13, PL n = 11)	CIT 10 g/day 4 weeks + CIT + SVLIRT 4 weeks	Resistance training (slow velocity, low-intensity leg exercises)	Low-intensity	2 sessions/week, 4-week supplementation + 4-week combined intervention	sfemFMD, leg LM, leg curl strength	sfemFMD ↑, LM ↑, Leg curl strength ↑	Small cohort; combination study limits attribution to CIT vs. exercise; additive benefits observed, hypothesis-generating	(Kang et al. 2022)
22 postmenopausal women	CIT 10 g/day vs. placebo, 4 weeks	Isometric handgrip (IHG) + Post-exercise muscle ischemia (PEMI)	Low-intensity	Single session assessment during IHG/PEMI; 4-week supplementation	Aortic SBP, PP, Pf & Pb pressure waves	SBP ↓, PP ↓, Pf ↓, Pb ↓	Acute & subacute hemodynamics assessed; mechanistic insight inferred from pressure wave analysis; hypothesis-generating	(Dillon et al. 2024)
21 hypertensive postmenopausal women	CIT 10 g/day vs. placebo, 4 weeks	Plantarflexion exercise (PFE)	5%, 15%, 30% of 1RM	3-minute stages during PFE; 4-week supplementation	Macro- & microvascular FMD, BF, VC	FMD ↑, 5 s peak velocity ↑, Flow ↑; BF & VC ↑ at 15% & 30% PFE, ↔ at 5% PFE	Improvements in microvascular function drove exercise BF/VC; small sample; acute vs. chronic effects not distinguished	(Dillon et al. 2024)
41 obese postmenopausal women, high BP	WBVT, CIT, WBVT + CIT, 8 weeks	Whole-body vibration + L-Citrulline	WBVT: 4 leg exercises, moderate	3 sessions/week	cfPWV, faPWV, leg LM index, leg strength, BF%	cfPWV ↓, faPWV ↓, LM ↑, Leg strength ↑, BF% ↓; additive effect with WBVT + CIT	Combination effects limit attribution to CIT alone; older and obese population	(Figueroa et al. 2015)
42 postmenopausal women with prehypertension	Resistance training + Citrulline-Malate 8 g/day, 8 weeks	Resistance training, 7 exercises	45–55% 1RM	3 sessions/week, 3 sets x 10–12 reps	SBP, DBP, NO, VEGF	SBP ↓, DBP ↓, NO ↑, VEGF ↑; exercise alone ↔ SBP/DBP	Multiple small groups; effect of exercise vs. supplementation disentangled; only submaximal endurance responses measured	(Behpoor et al. 2020)
41 obese postmenopausal women	WBVT, CIT, WBVT + CIT, 8 weeks	Whole-body vibration + L-Citrulline	Moderate WBVT	3 sessions/week	Brachial & aortic BP, AP, AIx, AIx@75, NOx	BP ↓, AP ↓, NOx ↑; AIx & AIx@75 ↓ with WBVT + CIT, ↔ with CIT alone	Combined effect reduces pressure wave reflection; small sample; additive effects complicate attribution	(Wong et al. 2016)
56 dynapenic-obese older adults	HIIT	HIIT (elliptical)	High intensity	12-week program	Functional capacity, muscle strength, power	Upper limb strength ↑, walking speed ↑; functional capacity ↑; greater gains with HIIT + CIT than HIIT alone	No long-term follow-up; mechanisms of CIT effect not fully explored; sex-specific responses not detailed	(Buckinx et al. 2018)
25 older adults (13 women, 12 men)	HIIT + CIT 10 g/day vs. HIIT + PLA, 12 weeks	Calf exercise	Submaximal lower-limb exercise	Short-term, crossover	Femoral BF, vascular conductance (FVC), plasma Arg, BP	BF ↑, FVC ↑, diastolic BP ↓ in men; ↔ in women	Sex-specific effect; short-term intervention; baseline BP adjustment affected significance; modest improvements	(Gonzales et al. 2017)
33 older women, ≥ 65 yr	Multicomponent training + CIT malate 3 g/day vs. PL, 6 weeks	Multicomponent exercise	Moderate	3 sessions/week	Physical function (6MWT, sit-to-stand, SPPB), serum biomarkers (vit D, CK, glucose, hormones), QoL	Sit-to-stand ↑, 6MWT ↑, SPPB ↑, Vit D ↑; metabolic & hormonal trends ↑; QoL ↑	Pilot study; mostly non-significant differences; small sample; short-term	(Ramos-Hernández et al. 2025)
15 hypertensive postmenopausal women	Acute CIT 6 g vs. PL, crossover, single session	Plantarflexion exercise + cold pressor test	Submaximal leg exercise	Single session	Brachial & aortic BP, femoral BF, FVC	Aortic SBP ↓, brachial SBP ↓, MAP ↓; FBF & FVC ↔	Small sample; acute study; exercise alone did not change flow; limited generalizability	(Maharaj et al. 2021)
23 older women, low BMI	Exercise + CIT 0.8 g + LEU 1.6 g/day vs. PL, 20 weeks	Weight-bearing & square stepping exercise	Moderate	75 min/week	Body composition, physical activity, plasma amino acids	Body weight ↑, BMI ↑, body mass ↑, household & total PA ↑, phenylalanine ↑	Small sample; low frequency of exercise (once/week)	(Kim et al. 2021)
81 obese older adults	HIIT ± CIT (10 g/day), 12 weeks	HIIT (elliptical trainer)	High	12 weeks	Muscle strength & power, lean mass, fat mass, waist circumference, mitochondrial markers, adipose tissue gene expression	Functional capacity ↑, lean mass ↑, muscle power ↑, waist ↓; HIIT + CIT: fat mass ↓, handgrip & quadriceps strength ↑	Mixed-sex sample; highly controlled setting; results may vary in real-world	(Marcangeli et al. 2022)
42 postmenopausal women	Resistance training + CIT-malate 8 g/day vs. PL, 8 weeks	Resistance training	45–55% 1RM	3 sessions/week	Serum BDNF, NO, estrogen	Estrogen ↑, NO ↑, BDNF ↑ (exercise+supplement > exercise or supplement alone)	Quasi-experimental; multiple groups; small sample per group	(Sedighi et al. 2020)

CIT, L-citrulline; CIT·LEU, L-citrulline + leucine; PL, placebo; HIIT, high-intensity interval training; WBVT, whole-body vibration training; 1RM, one-repetition maximum; PA, physical activity; LM, lean mass; BF, blood flow; VC, vascular conductance; FMD, flow-mediated dilation; NO, nitric oxide; VEGF, vascular endothelial growth factor; BDNF, brain-derived neurotrophic factor; SBP, systolic blood pressure; MBP, mean arterial pressure; EX, exercise; SPPB, short physical performance battery; 6MWT, six-minute walk test; AP, augmentation pressure; AIx, augmentation index; AIx@75, AIx adjusted to 75 beats/min

Effects of L-citrulline on peripheral and central hemodynamic responses during exercise in postmenopausal women

To facilitate interpretation of the evidence, exercise responses are categorized into acute hemodynamic effects and chronic training adaptations. Acute effects, such as transient increases in blood flow and NO bioavailability, reflect immediate vascular responses to single exercise sessions. In contrast, chronic adaptations, including structural vascular remodeling, improvements in arterial stiffness, and enhanced muscle strength, arise from repeated exercise over time. This distinction is important, as acute and chronic responses may involve different mechanisms and have distinct clinical implications in postmenopausal and older women.

Kang et al.(Kang et al. 2024) demonstrated that acute supplementation of L-citrulline (10 g/day for a duration of 4 weeks, n = 22) resulted in a significant enhancement of macrovascular endothelial functionality, as demonstrated by an increase in flow-mediated dilation (FMD) (Δ1.6 ± 0.7% compared to Δ−0.7 ± 0.6%, P < 0.05) and a reduction in aortic SBP (Δ−4 ± 6 versus Δ3 ± 5 mmHg) at rest. During physical exertion, L-citrulline was observed to augment femoral blood flow (Δ48 ± 16 versus Δ17 ± 12 mL/min), vascular conductance (Δ41 ± 14 versus Δ−21 ± 9 mL/mmHg/min), and forearm muscle oxygenation (tissue saturation index, TSI) (Δ1.61 ± 0.46% versus Δ−0.84 ± 0.58%; deoxygenated hemoglobin, Δ−2.76 ± 0.77 versus Δ1.03 ± 0.69 µM). Furthermore, exercise-induced blood flow and vascular conductance exhibited a positive correlation with FMD and TSI (P < 0.05), indicating that the observed enhancement in endothelial functionality may facilitate improved oxygen delivery to the musculature. Despite the encouraging nature of these findings, it is imperative to acknowledge that they are preliminary in nature due to the limited sample size and the brevity of the intervention period (Kang et al. 2024). In a small randomized investigation, Dillon et al.(Dillon et al. 2024) (n = 22), a 4-week regimen of L-citrulline (10 g/day) supplementation was evaluated against a placebo to assess its influence on aortic SBP, pulse pressure, as well as forward and backward wave pressures during isometric handgrip and post-exercise muscle ischemia. The administration of L-citrulline resulted in a significant reduction of ΔSBP (− 9 ± 2 vs. −1 ± 1 mmHg, P = 0.006), Δ pulse pressure (− 5 ± 2 vs. 0 ± 1 mmHg, P = 0.03), Δ backward (− 6 ± 2 vs. −1 ± 1 mmHg, P = 0.01), and Δ backward (− 3 ± 1 vs. 0 ± 1 mmHg, P = 0.02) when compared to the placebo group. The observed correlations between Δ pulse pressure and both Δ forward and Δ backward (r > 0.72, P < 0.001) indicate that L-citrulline may mitigate pulsatile load through the modulation of the amplitudes of forward and backward pressure waves. Although these findings are preliminary due to the limited sample size, they provide support for the hypothesis that L-citrulline has the potential to enhance vascular responses to exercise-induced stress in postmenopausal women.

In another randomized investigation (n = 21), a 4-week regimen of L-citrulline supplementation (10 g/day) was compared to a placebo in order to assess FMD and microvascular functionality, as well as blood flow and vascular conductance during plantarflexion exercise at 5%, 15%, and 30% of one-repetition maximum. The administration of L-citrulline resulted in a statistically significant enhancement of resting FMD (Δ1.28 ± 0.42 vs. Δ0.01 ± 0.40%, P = 0.04) and microvascular reperfusion velocity and flow (all P < 0.05). L-citrulline notably intensified blood flow and vascular conductance responses during moderate (15%) and high-intensity (30%) plantarflexion exercise (all P < 0.01), while low-intensity (5%) exercise exhibited no significant changes. The observed correlations between microvascular enhancements and exercise-induced blood flow/vascular conductance imply that the beneficial effects of L-citrulline on lower limb perfusion are predominantly facilitated through microvascular mechanisms. Although these findings are preliminary, they underscore the potential of L-citrulline as an intervention aimed at improving vascular responses and muscle perfusion in hypertensive postmenopausal women (Dillon et al. 2024). A randomized, double-blind, crossover investigation aimed to ascertain whether short-term administration of L-citrulline (6 g/day for a duration of 14 days, n = 25; comprising 12 males and 13 females) facilitates an enhancement in exercise-induced muscle perfusion and vascular conductance in older individuals by augmenting L-arginine availability for nitric oxide biosynthesis. Plasma concentrations of arginine exhibited a significant increase in both genders (with women experiencing a + 30% rise and men a + 35% increase, P < 0.01), while enhancements in femoral blood flow (+ 11%) and vascular conductance (+ 14%) during calf exercises were exclusively identified in males (P < 0.05). Diastolic blood pressure demonstrated a reduction in males, whereas it remained stable in females. The lack of effect observed in females underscores the presence of sex-specific vascular responses, potentially modulated by baseline hemodynamic parameters. When adjusting for baseline diastolic pressure, the differences in blood flow diminished, indicating a partial reliance on resting vascular tone. The results suggested that L-citrulline provides a modest enhancement of submaximal exercise perfusion in older males, which may contribute to improved muscle metabolism and exercise tolerance; however, the observed effects are limited and exploratory in nature. As the cohort included both sexes, the results should be interpreted cautiously regarding female-specific responses (Gonzales et al. 2017). Acute ingestion of L-citrulline (6 g) among a cohort of 15 women significantly diminished the aortic and brachial SBP and mean arterial pressure responses during a combined protocol of plantarflexion exercise and cold pressor test (P < 0.05), while not influencing femoral blood flow or vascular conductance, thereby implying a prospective function in alleviating left ventricular overload amidst sympathetic activation. In a separate investigation, chronic administration of L-citrulline in conjunction with leucine (L-citrulline + leucine; 0.8 g + 1.6 g, administered bi-daily) over a duration of 20 weeks, combined with a regimen of low-frequency exercise (n = 10), resulted in an increase in body weight, body mass index (BMI), total body mass, household and total physical activity, as well as plasma phenylalanine levels (P < 0.05) in older women exhibiting low BMI. These results suggested that acute L-citrulline may have the capacity to modulate hemodynamic stress, while chronic L-citrulline + leucine in conjunction with exercise may facilitate improvements in body composition and physical activity levels, potentially serving to alleviate sarcopenia and frailty in older women (Maharaj et al. 2021).

Although responsiveness varies according to sex, baseline vascular health, and exercise modality, the collective evidence supports a central role for NO-mediated mechanisms linking improved vascular function to enhanced exercise tolerance and safety. However, these adaptations are likely multifactorial: associative evidence suggests that oxidative stress balance, sympathetic nervous system activity, and vascular remodeling also contribute to the observed physiological responses (Moncada and Higgs 1993, Kingwell 2000, Sandri et al. 2016). While NO may play a key role, these additional factors highlight the complexity of exercise-induced adaptations and indicate that current mechanistic findings are primarily hypothesis-generating. These findings provided a strong physiological rationale for incorporating L-citrulline into exercise-based interventions aimed at improving cardiovascular and functional outcomes in postmenopausal populations.

Endothelial function and arterial stiffness responses to L-Citrulline supplementation and exercise

In a randomized controlled trial (n = 41), the discrete and synergistic effects of whole-body vibration training (WBVT) and L-citrulline supplementation were meticulously examined over an 8-week period. The combination of WBVT and L-citrulline yielded the most substantial improvements, resulting in a significant reduction in aortic pulse wave velocity (cfPWV: −0.91 ± 0.21 m/s, P < 0.01) and an enhancement in leg lean mass index (Δ2.7 ± 0.5%, P < 0.001), with the observed decreases in cfPWV being positively correlated with the increase in lean mass (r = − 0.63, P < 0.05). Both cohorts receiving WBVT exhibited marked enhancements in leg strength (~ 37%, P < 0.001) and a notable decrease in fat mass (~ 2%, P < 0.01), while the effects of L-citrulline administration alone were minimally impactful. These results indicate that WBVT serves as an effective modality for enhancing muscular function, and when utilized in conjunction with L-citrulline, it demonstrates a synergistic effect in diminishing aortic stiffness, thereby underscoring its potential as an intervention to alleviate cardiovascular risk and physical disability among obese postmenopausal women (Figueroa et al. 2015). Central and peripheral blood pressures, augmentation pressure, AIx, AIx normalized to a heart rate of 75 bpm (AIx@75), and circulating NO metabolites were assessed to evaluate vascular function. A research investigation assessed the independent and synergistic effects of WBVT and L-citrulline (10 g/day) conducted over a duration of 8 weeks on aortic hemodynamics and plasma nitric oxide metabolites (NOx). Participants were randomly assigned to one of three groups: L-citrulline, WBVT combined with a placebo, or WBVT paired with L-citrulline. All intervention strategies similarly resulted in a reduction of brachial and aortic systolic and diastolic blood pressure (BP) (P < 0.05) and an elevation in NOx levels. Only the groups receiving WBVT exhibited a decrease in AIx and AIx adjusted to 75 beats/min (AIx@75, P < 0.01), with the WBVT + L-citrulline group displaying the most significant enhancement (ΔAIx@75 − 10.5%±8.8%, P < 0.05 compared to L-citrulline alone). These findings imply that WBVT contributes to improved arterial compliance, whereas L-citrulline alone leads to a modest reduction in BP without influencing wave reflection. The results are encouraging yet preliminary, emphasizing the potential of the combined intervention of WBVT + L-citrulline to alleviate cardiovascular risk among obese postmenopausal women (Wong et al. 2016). These potentially complementary effects underscore the importance of combined nutritional and exercise strategies for optimizing vascular health in postmenopausal women at elevated cardiometabolic risk.

Synergistic effects of L-citrulline and exercise on muscle mass, strength, and functional performance

Age- and menopause-related declines in muscle mass, strength, and physical performance increase frailty and reduce independence. These changes are worsened by sedentary behavior, obesity, and cardiometabolic disorders. While exercise is the primary strategy to counteract sarcopenia, nutritional interventions like L-citrulline may further enhance muscle perfusion, anabolic signaling, and training adaptations. Evidence derived from a limited randomized controlled trial (n = 24) indicates that L-citrulline (10 g/day) facilitates enhancements in leg endothelial functionality, quantified through superficial femoral artery flow-mediated dilation (sfemFMD), subsequent to a 4-week intervention in comparison to a placebo (Δ1.8 ± 0.3% vs. Δ − 0.2 ± 0.5%, P < 0.05). Furthermore, when L-citrulline was administered in conjunction with slow-velocity low-intensity resistance training (SVLIRT) for an additional 4 weeks, synergistic advantages were noted in terms of leg lean mass (Δ0.49 ± 0.15 kg vs. Δ0.07 ± 0.12 kg, P < 0.05) and leg curl strength (Δ6.9 ± 0.9 kg vs. Δ4.0 ± 1.0 kg, P < 0.05). These results imply that L-citrulline may augment vascular adaptations and, when paired with SVLIRT, may lead to modest improvements in both muscle mass and strength. Nonetheless, the conclusions derived from this study should be regarded as preliminary due to the restricted sample size and the brief duration of the intervention (Kang et al. 2022). In older adults characterized by dynapenic obesity (n = 56; age range 65–68 years), the progressive deterioration of muscle mass and functional capabilities significantly undermines overall functional capacity. A randomized controlled trial evaluated the effects of a 12-week regimen of high-intensity interval training (HIIT) compared to a combined approach of HIIT and L-citrulline supplementation (10 g/day) on various parameters including body composition, muscle strength, power, and functional performance. Both intervention groups exhibited improvements in functional and aerobic capacities; however, the HIIT combined with L-citrulline cohort demonstrated significantly enhanced performance in the fast-paced Timed Up & Go assessment (p = 0.04) as well as in upper limb strength (both absolute and relative measures, P = 0.05). The observed additive benefits imply that L-citrulline supplementation may augment NO-mediated vasodilation, increase the availability of amino acids, and improve muscle perfusion, thereby potentially facilitating superior strength adaptations. It is important to note that these findings remain preliminary due to the moderate sample size and the limited scope of mechanistic evaluation. Further research is warranted to explore long-term effects, sex-specific responses, and interactions with energy balance. In conclusion, the integration of HIIT with L-citrulline supplementation may serve to optimize functional outcomes in frail or dynapenic older adults. Since the study included both men and women, the applicability of these results specifically to postmenopausal women remains uncertain (Buckinx et al. 2018).

A 20-week randomized, double-blind, placebo-controlled investigation assessed the impacts of concomitant L-citrulline and leucine supplementation in conjunction with exercise on body composition, physical activity, and amino acid profiles in elderly Japanese females exhibiting a low BMI (16–21 kg/m², n = 23). Participants were administered either L-citrulline· leucine (0.8 g L-citrulline + 1.6 g leucine, twice daily) or a placebo alongside a regimen of weekly weight-bearing and square-stepping exercises (75 min). The L-citrulline· leucine group demonstrated statistically significant enhancements in body weight, BMI, total body mass, household and overall physical activity, as well as plasma phenylalanine concentrations in comparison to the placebo group (P < 0.05). These findings suggested that the integration of amino acid supplementation and exercise may facilitate protein synthesis, encourage the accrual of lean mass, and elevate levels of physical activity, thereby providing a mechanistic framework for the prevention of sarcopenia and frailty in older women with a low BMI. Additional research is necessary to validate long-term functional outcomes (Kim et al. 2021). A research examined the effects of a 12-week regimen of HIIT, both with and without the addition of L-citrulline (10 g/day), on muscle functionality, body composition, and mitochondrial quality control among 81 obese older adults (mean age approximately 67 years). Both HIIT cohorts exhibited significant enhancements in functional capacities, leg lean mass, muscle power, and waist circumference (all P < 0.05). The combination of HIIT and L-citrulline uniquely augmented handgrip and quadriceps strength (+ 4.3% and + 10.3%, respectively) and resulted in a reduction of fat mass (− 1.0%, P < 0.05). Muscle biopsies revealed increases in mitochondrial content, fusion events, and mitophagy in both groups, while the HIIT + L-citrulline group additionally demonstrated a significant decrease in CIDEA expression (P < 0.001). These results indicated that HIIT serves as an effective modality for enhancing functional and mitochondrial metrics, with L-citrulline supplementation providing supplementary advantages in muscle strength and fat reduction, thereby underscoring a viable intervention to alleviate age- and obesity-related muscular impairments. However, the study included both male and female older adults, and sex-specific effects were not separately analyzed. Therefore, these findings may reflect general aging-related responses rather than outcomes exclusively in postmenopausal women (Marcangeli et al. 2022).

Molecular and neurovascular mechanisms of L-citrulline–exercise interactions

Menopause is accompanied by hormonal and molecular changes that negatively affect vascular integrity, neurovascular signaling, and metabolic health. Declines in estrogen, reduced NO bioavailability, impaired angiogenic signaling, and altered neurotrophic support contribute to endothelial dysfunction, reduced exercise responsiveness, and increased cardiometabolic risk. Combining structured exercise with L-citrulline supplementation has emerged as a promising strategy to modulate key biochemical mediators, including NO, vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and sex hormones. Here, we summarize clinical evidence linking these molecular and neurovascular mechanisms to functional outcomes in postmenopausal women. In a cohort of postmenopausal females exhibiting prehypertension (n = 42, mean age 53 ± 2 years), the impact of an eight-week regimen of resistance training supplemented with citrulline-malate (8 g/day) was scrutinized concerning its effects on BP, NO, and VEGF at rest and during submaximal endurance exercise. The participants were systematically randomized into six distinct groups, encompassing exercise + supplement, exercise + placebo, and control groups. Although resistance training in isolation did not yield statistically significant modifications in BP, NO, or VEGF responses, citrulline-malate supplementation demonstrably resulted in reductions in both systolic and diastolic BP, whilst concurrently augmenting NO and VEGF levels during exercise (P < 0.05). The combined intervention of exercise and supplementation manifested additive effects, indicating that citrulline-mediated enhancement of NO bioavailability may bolster endothelial function and vascular reactivity beyond the effects of training alone. These findings remain preliminary due to the limited sample size and brief duration of the intervention; however, they underscore the potential mechanistic interplay between resistance exercise and citrulline supplementation in enhancing vascular health and endothelial-mediated hemodynamic responses in prehypertensive postmenopausal women (Behpoor et al. 2020).

Another randomized, double-blind, placebo-controlled pilot study (n = 33, women aged 65 years and above) investigated the effects of six weeks of multicomponent training supplemented with 3 g/day of citrulline malate on various parameters including physical function, biochemical markers, and overall quality of life. While the majority of intergroup discrepancies did not reach statistical significance, the citrulline malate group exhibited clinically relevant enhancements in sit-to-stand performance (P = 0.023, δ = 1.38), distance covered in the 6-Minute Walk Test (an increase of + 61 m), and scores on the Short Physical Performance Battery (δ = 1.05). Additionally, serum levels of vitamin D demonstrated an increase (+ 3.82 ng/mL), alongside trends indicative of advantageous metabolic and hormonal adjustments. Improvements in quality of life were predominantly noted in the physical and environmental dimensions. These results imply that short-term supplementation with citrulline malate may positively influence exercise-induced functional and biochemical outcomes among older female populations. Nevertheless, the limited sample size and brief duration of the intervention constrain the generalizability of these findings, thereby necessitating further investigation to validate efficacy and clarify the underlying mechanisms involved (Ramos-Hernández et al. 2025). Sedighi et al.(Sedighi et al. 2020) assessed the ramifications of an eight-week regimen of resistance training (RT, 45–55% 1RM, 3 sessions per week) in conjunction with citrulline malate supplementation (8 g/day, n = 42) on serum levels of estrogen, NO, and BDNF. Participants were systematically assigned to six distinct groups (Exercise + Supplement, Exercise + Placebo, Exercise, Supplement, Placebo, Control). The results indicated that the combination of RT and citrulline supplementation resulted in a statistically significant elevation of estrogen, NO, and BDNF compared to the effects of either intervention administered in isolation (P < 0.001). Notably, exercise undertaken alone led to an increase in estrogen in comparison to supplementation alone; however, alterations in NO and BDNF were not found to be statistically significant. These findings imply that citrulline may enhance exercise-induced endocrine and neurotrophic adaptations, thereby supporting synergistic advantages on vascular function and neuroplasticity in postmenopausal women. The investigation underscores the potential efficacy of integrated nutritional and exercise strategies in alleviating age-associated physiological deterioration.

Potential influence of sex hormones on L-citrulline and exercise responses

Postmenopausal women undergo a substantial decrease in estrogen levels, which is implicated in the pathophysiology of endothelial dysfunction, heightened arterial stiffness, and diminished muscle perfusion (Halligan et al. 2004, Velders and Diel 2013). Estrogen is regarded as a facilitator of the cardiovascular advantages associated with physical exercise, as it enhances the bioavailability of NO and fosters vasodilation, potentially working in concert with interventions such as L-citrulline supplementation (Lew et al. 2022, Dillon et al. 2024). Consequently, fluctuations in sex hormone levels, including the administration of hormone replacement therapy, could significantly modulate the efficacy of combined L-citrulline and exercise interventions. Nevertheless, our thorough literature review has revealed that no clinical or preclinical research has specifically examined the interplay between sex hormone status and the cardiovascular or muscular responses to the conjunction of L-citrulline and exercise in postmenopausal women. Further investigations are essential to elucidate this prospective modulatory effect.

Determinants of individual responsiveness to combined L-citrulline and exercise interventions in postmenopausal women

Although the clinical trials reviewed in this article collectively support a beneficial interaction between L-citrulline supplementation and exercise in postmenopausal and older women, the magnitude and nature of observed responses are not uniform across studies. This variability appears to arise from differences in baseline physiological status, exercise characteristics, and contextual factors that shape individual responsiveness. Understanding these determinants is critical for interpreting the clinical relevance of combined exercise–nutrition strategies beyond isolated outcome measures. One of the most consistent modifiers of response is baseline vascular health. Trials conducted in hypertensive or obese postmenopausal women tend to demonstrate clearer improvements in exercise-related hemodynamics, arterial stiffness, and central blood pressure regulation compared with studies involving healthier or normotensive older women (Kang et al. 2024, Dillon et al. 2024, Figueroa et al. 2015, Kang et al. 2022). This pattern suggests that L-citrulline may exert its greatest functional impact in individuals with pre-existing endothelial dysfunction, where NO availability represents a limiting factor for vascular adaptability. In contrast, in populations with relatively preserved vascular function, supplementation appears to increase circulating arginine without necessarily translating into measurable functional gains during exercise (Gonzales et al. 2017). Exercise modality and intensity also emerge as important determinants of responsiveness. Interventions involving moderate-to-high metabolic or mechanical stress—such as resistance training, WBVT, or HIIT —more consistently reveal additive effects of L-citrulline on vascular or muscular outcomes compared with very low-intensity exercise paradigms (Kang et al. 2022, Buckinx et al. 2018, Marcangeli et al. 2022). This observation aligns with the concept that L-citrulline does not independently drive adaptation, but rather amplifies endogenous responses triggered by a sufficient physiological stimulus. Muscle phenotype and functional reserve represent another layer of heterogeneity. Studies enrolling women with dynapenia, obesity, or low muscle reserves tend to report more pronounced benefits of combined interventions on strength, mobility, or body composition compared with cohorts of physically active or less impaired older women (Buckinx et al. 2018, Kim et al. 2021). These findings imply that baseline anabolic sensitivity and muscle perfusion capacity influence the degree to which nutritional support enhances training responsiveness. In this context, L-citrulline may help overcome physiological constraints that otherwise blunt exercise-induced improvements in vulnerable populations. Temporal characteristics of supplementation further contribute to divergent outcomes.

Chronic L-citrulline intake appears more likely than acute dosing to influence endothelial function, muscle oxygenation, and training adaptations, particularly when paired with repeated exercise exposure (Kang et al. 2024, Dillon et al. 2024, Dillon et al. 2024). Acute supplementation, may nonetheless attenuate exaggerated central blood pressure responses during combined physical and sympathetic stress, highlighting context-specific benefits rather than universal effects (Maharaj et al. 2021). These distinctions underscore that the timing and duration of supplementation shape which physiological domains are most responsive. Sex-specific and hormonal considerations are particularly relevant in mixed-sex studies that include older women. Evidence suggests that postmenopausal women may respond differently to L-citrulline than older men, even under similar supplementation protocols, potentially due to differences in baseline NO signaling, vascular stiffness, and hormonal milieu (Gonzales et al. 2017).

Safety, tolerability, and translational considerations of L-citrulline supplementation in exercise-based interventions

When considering the translation of L-citrulline supplementation into exercise-based interventions for postmenopausal and older women, issues related to safety, tolerability, and clinical applicability become particularly relevant. This domain requires a balanced interpretation of available evidence, emphasizing cautious optimism rather than definitive clinical recommendations. Across the clinical trials included in this review, L-citrulline was generally administered at doses ranging from approximately 3 to 10 g per day, either as free L-citrulline or in the form of citrulline malate. Within this range, supplementation was consistently well tolerated, with no serious adverse events reported in postmenopausal women, including those with hypertension or obesity. Importantly, several studies employing moderate-to-high daily doses did not report gastrointestinal discomfort, hypotension, or exercise intolerance, suggesting a favorable safety profile in these populations (Allerton et al. 2018). From a cardiovascular safety perspective, the interaction between L-citrulline supplementation and blood pressure regulation warrants particular attention. In hypertensive postmenopausal women, combined L-citrulline and exercise interventions were often associated with modest reductions in resting or exercise-induced blood pressure responses, rather than excessive hypotensive effects. Acute and chronic supplementation appeared to attenuate exaggerated pressor responses during sympathetic or exercise stress without compromising peripheral blood flow. These findings suggest that L-citrulline may enhance hemodynamic control rather than induce clinically concerning reductions in blood pressure, particularly when used alongside structured exercise (Dillon et al. 2024, Figueroa et al. 2015). Dose considerations are central to both safety and clinical applicability. Evidence from metabolic and protein synthesis studies indicates that L-citrulline doses below 3 g per day may be insufficient to elicit consistent physiological effects, whereas doses between 3 and 10 g per day are most commonly associated with increases in plasma citrulline and arginine availability (Allerton et al. 2018). Higher doses, up to approximately 15 g per day, appear to be well tolerated in healthy adults; however, pharmacokinetic evidence indicates diminishing returns beyond this range, potentially due to saturation of transport mechanisms or renal conversion to arginine (Moinard et al. 2008). These observations underscore the need for conservative dosing strategies in clinical contexts, particularly when supplementation is combined with exercise in older women. An additional consideration relates to the comparison between L-citrulline and other NO–related supplements. High doses of L-arginine have been associated with gastrointestinal intolerance, whereas L-citrulline appears to increase arginine bioavailability more efficiently and with fewer reported side effects (Allerton et al. 2018). Together, these data support the preferential use of L-citrulline as a safe and effective NO precursor in exercise interventions aimed at improving vascular and muscular function in postmenopausal women.

Limitations and future directions

Closely related to duration is the characterization of study populations. The majority of trials have focused on postmenopausal women with elevated cardiometabolic risk profiles, including hypertension, obesity, dynapenia, or low physical fitness (Figueroa et al. 2015, Kang et al. 2022, Buckinx et al. 2018). While this focus enhances clinical relevance for high-risk groups, it also limits generalizability to healthier postmenopausal women or those in earlier stages of menopausal transition. Baseline physiological status likely influences responsiveness, so extrapolating findings across the broader postmenopausal spectrum should be approached with caution. Another important consideration concerns the nature of outcome measures emphasized in current studies. Much of the existing evidence relies on intermediate physiological or functional endpoints such as indices of vascular function, muscle strength tests, or biochemical markers, that are mechanistically informative but not equivalent to definitive clinical outcomes (Wong et al. 2016, Behpoor et al. 2020). While these measures provide valuable insight into biological plausibility, their direct translation to long-term clinical outcomes remains unclear. This distinction does not diminish the value of current findings but highlights the interpretive boundary between mechanistic adaptation and clinical impact. At the mechanistic level, several studies have examined isolated molecular or hormonal markers in response to combined interventions (Ramos-Hernández et al. 2025, Sedighi et al. 2020). However, the integration of vascular, muscular, neurotrophic, and endocrine adaptations within a unified framework remains limited. This limitation underscores the need for integrative assessments that link molecular and physiological adaptations to functional outcomes. Despite these considerations, the reviewed literature collectively introduces a meaningful conceptual advance. The studies emphasize L-citrulline’s role as a modulator of exercise responsiveness, positioning supplementation within a broader lifestyle-based intervention strategy. This integrative perspective represents an important step forward, particularly for postmenopausal women, in whom concurrent vascular, musculoskeletal, and hormonal alterations necessitate multifaceted approaches. Building on these limitations, several future research directions emerge. Longitudinal randomized trials with extended follow-up periods are needed to determine whether early physiological adaptations translate into durable functional benefits and reduced health risk over time (Dillon et al. 2024, Dillon et al. 2024, Marcangeli et al. 2022). Such studies would strengthen causal inference while maintaining relevance to real-world aging trajectories. Future investigations should also adopt phenotype-informed designs, stratifying participants based on baseline vascular health, muscle mass, physical function, or menopausal stage. This approach may clarify which subgroups derive the greatest benefit from combined exercise and L-citrulline strategies, thereby supporting more personalized intervention models (Figueroa et al. 2015, Kang et al. 2022). In addition, research that explicitly bridges mechanistic and functional domains would enhance interpretability and provide a clearer understanding of translational relevance. Finally, expanding studies into community-based or pragmatic settings may improve translational relevance by capturing adherence, feasibility, and behavioral sustainability alongside physiological outcomes. In conclusion, while current evidence cautiously supports the potential of L-citrulline as an adjunct to exercise in postmenopausal women, thoughtful attention to study design, population diversity, and outcome relevance will be essential for advancing the field. Such considerations are crucial for developing integrative, evidence-informed strategies to promote healthy aging and preserve functional independence. Although various exercise modalities are discussed together, it should be noted that resistance training, HIIT, and WBVT likely elicit different vascular and muscular adaptations. The current evidence does not allow definitive conclusions regarding modality-specific effects, which represents a limitation of this review.

Conclusion

The present review highlights that combining L-citrulline supplementation with structured exercise may enhance vascular, muscular, and molecular outcomes in postmenopausal women. Evidence suggests improvements in endothelial function, arterial stiffness, muscle mass, strength, and neurovascular signaling, particularly in populations with reduced muscle reserves or cardiometabolic risk. These effects are likely mediated by increased NO bioavailability, angiogenic and neurotrophic signaling, and favorable hormonal adaptations. While responses vary according to exercise type, supplementation protocol, and baseline health, integrated exercise–nutrient interventions represent a promising strategy to mitigate age- and menopause-related functional declines. Further research is needed to optimize protocols and confirm long-term benefits.

Author contributions

Zhigang Chen conceptualized the review topic, conducted the literature search, screened and selected relevant studies, and drafted the initial version of the manuscript. The author performed critical analysis and synthesis of the evidence, prepared figures/tables, and wrote all sections of the review. Zhigang Chen revised the manuscript for intellectual content and approved the final version for submission. All authors reviewed the manuscript.”

Funding

This research received no external funding.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Conflict of interest

The authors declare no competing interests.

Ethical approval and consent to participate

Not applicable.

Consent for publication

Not applicable.