Table 1.

Findings about the consumption of ‘superfoods’ on the metabolic control of TD2M.

Food	Year and Country/Type of Review (Total Number of References)	Objective(s)	Examples of Clinical Evidence	Main Findings: Effect on Type 2 Diabetes and Other Related Diseases
Blueberries [13]	Canada, United Kingdom, USA, Spain Narrative review (n = 198 references)	To review the role of blueberries in cardiometabolic health.	Biomarkers: improved insulin sensitivity, plasma lipid profiles and reduced plasma markers of oxidative stress (for both short- and long-term interventions).	A reduced risk of type 2 diabetes, cardiovascular disease, weight gain and death were reported. As well, neuroprotection and vision (in less extended) benefits.
Bilberry [14]	China Narrative review (n = 100 references)	To review the potential effects of bilberry supplementation on metabolic and cardiovascular risk factors.	Anti-inflammatory and hypoglycemic effects (e.g., decreased postprandial glycaemia and insulin level). Improvement of hyperlipidaemia: increased HDL cholesterol and decreased LDL cholesterol. Reduced blood pressure.	Bilberry supplementation can present a positive effect on metabolic and cardiovascular risk factors.
Red Raspberry (RR) [15]	USA Narrative review (n = 60 references)	To investigate the potential metabolic benefits of dietary red raspberry in individuals with T2DM and prediabetes.	The consumption of 250 g of frozen RR with a high-fat breakfast meal reduced postprandial plasma glucose levels and area under the curve (AUC): individuals with either T2DM or prediabetes and overweight or obesity (2 RCTs). Reduction of low-density lipoprotein cholesterol (LDL-c) (32 RCT).	Improvements in glycaemia profile and insulin sensitivity, adiposity, lipid profiles, ectopic lipid accumulation, inflammation, oxidative stress and cardiac health.
Berries * [16]	Poland Narrative review, with application of PRISMA flow diagram (n = 329 references)	To summarise both clinical and non-clinical findings that the consumption of berries, berry extracts, purified compounds, juices, jams, jellies and other berry byproducts aided in the prevention or otherwise management of T2DM.	Glucose-lowering and insulin sensitivity improvements. Lower of dyslipidaemia markers. Anti-obesity. Reduced oxidative stress markers. Improvement in endothelial function of subjects with metabolic syndrome. Anti-inflammatory and anti-hypertensive. Daily recommended dose: 200 to 400 g (70 kg; middle-aged person). Reduction of HbA1c was reported with berries in some studies (strawberries, raspberry and Acai berries).	The consumption of berry products is effective to prevent and control metabolic hyperglycaemic and hyperlipidaemic conditions.
Food with polyphenols [17]	China Narrative review (n = 159 references)	To analyse how dietary polyphenols affect starch digestion.	Polyphenols can directly inhibit key digestive enzymes (α-glucosidase) and bind with starch; bounded polyphenols are still able to show the inhibitory activity against the enzymes (in vitro studies).	A better postprandial hyperglycaemia profile by polyphenols may be explained by both inhibited starch digestion and impact on glucose transport.
Foods with polyphenols * [18]	Italy Narrative review (n = 136 references)	To discuss the effect of polyphenol/phenolic compounds on the main cardiometabolic risk factors.	Epidemiological studies: polyphenol-rich diets seem to benefit the prevention of T2DM risk. Medium-term clinical trials (6–8 weeks) improve blood glucose, lipids and blood pressure (individuals with and without T2DM). Best results for long-term RCTs, with polyphenol-rich foods and beverages. Improvement of HbA1c (green tea, catechins or total polyphenols intake) in some trials.	Different polyphenol food subclasses seem to present a pleiotropic effect on cardiometabolic risk factors. Fasting glucose, insulin or HbA1c can be improved according to some trials.
Grapes and their derivatives (wine) [19]	Italy, Germany, Australia, France, Greece Narrative review (n = 62 references)	To confirm whether there is a difference between alcoholic beverages in inducing beneficial health effects in T2DM individuals and whether the consumption of alcoholic beverages can be included in the daily diet of diabetics.	A reduced risk of T2DM with light to moderate wine consumption (ten studies).	Wine was the alcoholic beverage with the most favourable outcomes. Light/moderate wine consumption is associated with improved metabolic control in T2DM individuals.
Short- and long-term intake of fermented dairy products * [20]	Canada, UAE, USA Narrative review (n = 47)	To evaluate the evidence from a cross-sectional analysis of longitudinal studies and human and animal experimental trials to further understand the current knowledge linking short- and long-term consumption of fermented dairy products to T2DM.	Cohort studies: protective effect of fermented dairy products on the prevention and control of T2DM, especially with yoghurt’s potential to decrease insulin resistance and improve glycemic control: improved glucose tolerance, fasting blood sugar, HbA1c (1.2% to 2% reduction) and 2 h postprandial glucose.	Higher intake of fermented dairy products may decrease the risk of developing T2DM in the long term. In the short term, improvements in the glycaemic control markers were also achieved. Yoghurt was the most consistent food protecting against T2DM.
Dairy products and plant proteins (e.g., legumes and soy) [21]	Italy and USA Systematic review (n = 50)	To evaluate the ideal protein quality and quantity and the dietary composition for the prevention and metabolic control of T2DM.	RR (relative risk) 95% CI of T2DM: 0.89 (0.84–0.94) total dairy products, 0.87 (0.78–0.96) whole milk, 0.83 (0.70–0.98) yoghurt and 0.74 (0.59–0.93) soy (women).	Higher intake of plant protein and dairy products is associated with a modestly reduced risk of T2DM. Red meat, processed protein foods and high-fat dairy products could have negative effects in the long term.
Both dairy and not-dairy products fortified with vitamin D * [22]	Iran and UK Systematic review and meta-analyses (n = 48)	To evaluate effects of Vitamin D fortification on indices of glycaemic control.	In total, 11 RCTs; the impact of enriched food with vitamin D (100 IU to 28,000 IU vitamin/day) on fasting serum glucose in diabetics was significant (mean difference: −2.772, p = 0.041, and 95% CI: −5.435 to −0.109) as well as on serum insulin (mean difference: −2.937; 95% CI:−4.695 to −1.178).	Vitamin D fortification of dairy products leads to an improvement in Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), fasting plasma glucose and HbA1C.
Fermented dairy products (FDFs) and probiotic supplementation * [23]	Spain Systematic review and meta-analysis (n = 107)	To study the relation between the regular consumption of FDFs and cardiometabolic diseases (CMD) risk factors (assessed by prospective cohort studies–PCSs), and the effect of probiotic supplementation added into a dairy matrix on CMD parameters (evaluated by RCTs).	In total, 20 PCSs and 52 RCTs. Probiotic intake in capsule/powder displayed a significant reduction on HbA1c changes. However, the effects of probiotic supplementation into a dairy matrix on diabetic parameters in T2DM subjects did not show significant results, regarding the alterations of fasting insulin, HbA1c and plasma CRP.	Yoghurt intake: reduced risk of T2DM and metabolic syndrome development. Fermented milk: reduced cardiovascular risk. Probiotic supplementation added into dairy matrices: can reduce lipid concentrations and anthropometric parameters. Probiotic capsule/powder supplementation: can favour T2DM management and reduce anthropometric parameters.
Yoghurt (enriched with probiotics) * [24]	Greece Narrative review (n = 97)	To present the RCTs which have been conducted in the last decade in patients with T2DM.	Significant reductions of HbA1 were reported in some trials. However, the number of trials is limited. Enrichment of yoghurts with vitamin D, calcium and probiotics (e.g., L. acidophilus and B. lactis during a short period of 4–12 weeks). Yoghurt enriched in flaxseed or complex B vitamins may have impact on glycaemia control.	The daily intake of yoghurt, especially when enriched with probiotics, vitamin D and calcium has a positive impact on the metabolic control of diabetic patients.
Fermented dairy (FD) foods rich in probiotics (e.g., cheese and yoghurt) [25]	Spain Narrative review (n = 76)	To evaluate the relationship between the FD products: yoghurt and cheese, and cardiometabolic risk factors obtained from meta-analyses, systematic reviews of prospective cohort studies (PCSs).	In all, 13 PCSs supported a potential protective role of yoghurt consumption and prevention of T2DM. Reduction in the risk of T2DM: 14% with a yoghurt intake of 80 g/d compared with no yoghurt intake and 22% with a yoghurt intake of 200 g/d (meta-analyses of PCSs).	Intake of yoghurt seems to be associated with a lower risk of developing type 2 diabetes. A lower risk of developing stroke and cardiovascular disease may be explained by the total consumption of FD.
Probiotics * [26] Dairy medium (e.g., goat’s milk, kefir and yoghurt); enriched with multiple probiotic strains).	USA Systematic review (n = 65)	To evaluate nine randomised controlled trials that tested the effects of probiotics on glycaemic outcomes and insulin resistance.	Nine randomised controlled trials. Improvement of insulin resistance; reduction of FPG, A1c, FPI and HOMA-IR with probiotic supplementation among subjects withT2DM.	Probiotic (dairy products and capsules) supplementation seems to favour metabolic control in adults with T2DM.
Whole cereals (e.g., wheat, rice, maize, barley, sorghum, millet, oat, rye, buckwheat) [27]	China, USA Narrative review (n = 384)	To highlight recent findings on the influences of both bioactive constituents and processing on the anti-diabetic effects and physiological properties of cereals.	The bioactive components of whole cereals, such as resistant starch, dietary fibre or β-glucan can contribute to reducing postprandial serum glucose and increasing insulin sensitivity.	Reduced risk of T2DM, with improvement of metabolic metabolism and lipidic profile.
Whole grains [28]	Italy, UK, Netherlands, Australia Systematic review (n = 75)	To systematically review current evidence on whole grain consumption and various health outcomes provided from meta-analyses of observational studies.	Whole grain consumption improves acute postprandial glucose and insulin homeostasis compared to similar refined foods in healthy subjects (meta-analysis of RCTs).	Strongest evidence: a decreased risk of T2DM and colorectal cancer with higher compared to lower dietary intake of whole grains. Possible: decreased risk of colon cancer, fatal coronary heart disease and cardiovascular disease (CVD) mortality.
Whole grains’ phenolic acids and dietary fibre (wheat, barley, oats, rice and buckwheat) [29]	China Narrative review (n = 172)	To review the existing literature on the linkages between the consumption of whole grains and the development of the following chronic non-communicable diseases: CVDs, obesity, T2DM and cancer.	Clinical and epidemiological studies support a positive association between the consumption of whole grains, phenolic acids and dietary fibres with a lower risk of disease. For instance, three or more servings of whole grains/day (20–30% lower risk of diseases).	The consumption of whole grains reduces the risk of CVDs, obesity, T2DM and cancer, with improved glycaemic control, and prevention of insulin resistance.
Dietary fibre and whole grains * [30]	New Zealand Systematic review and meta-analyses (n = 97)	To evaluate the role of high-fibre diets on mortality and increasing fibre intake on glycaemic control and other cardiometabolic risk factors of adults with prediabetes or diabetes.	Higher intakes of dietary fibre produced a reduced risk of premature mortality (prospective cohort studies) and improvement of glycaemic control and other risk factors for cardiovascular disease, such as cholesterol levels, HbA1c and body weight (controlled trials).	Improvement of glycaemic control and other risk factors for cardiovascular disease, such as cholesterol levels and body weight. Reduction of premature mortality.
Nuts (e.g., almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts) [31]	Turkey and Spain Narrative review (n = 64)	To provide an overview of recent findings on bioactive constituents, health claims and health benefits of nuts and dried fruits.	Reduction: total cholesterol; LDL-cholesterol; and triacylglycerols. No change: HDL and inflammation. No change/slight reduction: body weight and visceral adiposity (evidence from many studies). Epidemiologic studies (evidence from many studies): reduction of the risk of cardiovascular disease; coronary heart disease; cancer and all-cause mortality.	Nuts (e.g., 30 or 42.5 g/day without added salt or sugars) are potentially relevant to reduce total cholesterol, LDL and triacylglycerols (cardiovascular and coronary heart disease). The evidence regarding diabetes control improvement, including insulin sensitivity, is limited in clinical studies. The consumption of dried fruits presents similar benefits, although the level of evidence is more limited than for nuts.
Almond [32]	USA Comprehensive review (n = 131)	To provide an in-depth analysis of the effect of almonds on weight measures, metabolic health biomarkers and outcomes and the colonic microbiota.	RCTs (randomised controlled trials) are not consensual, regarding the benefits for glycaemic and HbA1s, with some studies showing positive results (and others not).	Consistent improvement of blood lipid profiles and modest reductions in blood pressure, but inconsistent and/or insignificant beneficial effects of glycaemic control, and HbA1c.
Pistachio [33]	Iran, Australia A systematic review and meta-analysis (n = 44)	To evaluate the effects of pistachio nuts on glycaemic control and insulin sensitivity in patients with T2DM, prediabetes and metabolic syndrome.	In all, 6 RCT; significant reduction in fasting blood glucose (FBG) and homeostasis model assessment of insulin resistance, but no significant improvement was observed with regard to hemoglobin A1c and fasting plasma insulin level.	Pistachio nuts might cause a significant reduction in fasting blood glucose and HOMA-IR, although HbA1c and fasting plasma insulin might not significantly improve.
Proteins * (especially plant protein rich diets) [34]	Germany, Australia, Finland, Sweden, Norway, Greece, Canada, USA, Croatia, Spain, Denmark Narrative review (n = 53)	To review the literature regarding protein intakes.	For instance, plant protein diet containing 65% plant protein, including 30% soy protein and 35% animal protein vs. control diet containing 30% plant and 70% animal protein (n = 41 participants); improvement in fasting glucose. Weight loss reduced HbA1c in all studies, although without significant differences between groups (high vs. low protein groups).	Protein rich diets, especially plant protein rich diets, improve the total levels of cholesterol and fasting blood glucose levels. High protein hypocaloric diets may moderately favour weight loss, when compared to lower protein hypocaloric diets, with a possible improvement in HbA1c and systolic and diastolic blood pressure.
Beans [35]	USA Narrative review (n = 96)	To provide an overview of the benefits of plant-based eating, with a concise focus on the nutritional properties unique to dry beans and their connection to improved health parameters of obesity including cardiovascular, metabolic, gastrointestinal gut health and low-grade inflammation.	Coronary heart disease (CHD) risk reduction and improved glycaemic control in T2DM patients.	The inclusion of beans in a plant-based diet presents a protective cardiovascular, metabolic and colon effect; improvement of obesity; management of immune-related disease and low-grade inflammation.
Chickpeas/Hummus (i.e., primarily chickpeas and tahini) [36]	USA Comprehensive review (n = 86)	To provide a comprehensive review of the scientific evidence examining the effects of acute and long-term consumption of hummus and hummus ingredients on diet quality and risk factors related to T2DM, cardiovascular disease and obesity.	Healthy adults (n = 10) consumed hummus (28, 56, 112, 259 g servings) with and without white bread vs. white bread alone: postprandial glucose AUC was lower for hummus alone < hummus and white bread < white bread alone. The 28 and 112 g servings of hummus also resulted in lower insulin AUC than the white bread serving (both, p < 0.05), but not with the 259 g serving (p > 0.05).	Improvement of postprandial glycaemic control, fasting lipids, appetite control and daily food intake with hummus compared to other consumed foods, such as white bread. Tahini showed a little impact on glucose control.
Whey protein * [37]	Iran A systematic review and meta-analysis (n = 54)	To assess the effects of whey protein on serum lipoproteins and glycaemic status in patients with metabolic syndrome (MetS) and related disorders.	Twenty-two studies: significant reduction of HbA1c, insulin and HOMA-IR, triglycerides levels, total cholesterol, LDL-cholesterol levels and total cholesterol/HDL cholesterol ratio.	The consumption of whey protein can improve HbA1c, insulin, HOMA-IR, triglycerides, total cholesterol, LDL cholesterol and total/HDL-cholesterol ratio in patients with MetS and related disorders.
Sunflower seeds and flax seeds [38]	Pakistan Narrative review (n = 21)	To determine the effect of sunflower seeds and flax seeds on T2DM.	For instance, 20 g/day of flaxseeds for three months reduced FPG concentrations, insulin resistance and insulin sensitivity.	Sunflower and flax seeds consumption can reduce glucose levels with better insulin resistance and improved insulin production.
Cabbage [39]	Mexico Narrative review (n = 201)	To analyse the effects of cabbage, and its bioactive compounds, on glucose homeostasis.	Improvement of glucose levels and oxidative stress and hypolipaemic markers.	Cabbage consumption can regulate glucose homeostasis.
Lupin * [40]	Australia, Systematic review (n = 37)	To investigate the effects of lupin on a range of health outcome measures.	There were 21 studies (998 participants): statistically significant decrease of glucose AUC in some studies. Benefits, such as satiety, glycaemic control or improved serum lipid profile and blood pressure were better with whole lupin.	The benefits on glycaemic control and serum lipid profile were moderate.
Prickly pear cacti (Opuntia spp.) cladodes [41]	Australia, UK, Greece, Italy Narrative review (n = 73)	To summarise the latest findings on the consumption of the prickly pear (PP; Opuntia spp.) cladode as a potential nutritional tool for the management of hyperglycaemia.	Reduction of glucose levels after prickly pear cladodes’ consumption (mainly acute studies).	Prickly pear cladodes show potential hypoglycaemic effects.
Honey [42]	Italy Narrative review (n = 112)	To summarise the current literature concerning the beneficial effects of honey in the management of the obesity-related dysfunctions, including neurodegeneration.	Honey significantly reduced plasma glucose concentration (especially, in the short term). However, plasma levels of haemoglobin A1c increased, after 8-week honey consumption in one clinical study.	Honey seems to improve glycaemic control and lipidic profile (honey acute effects/short term). Long-term clinical studies are limited.

* Reported potential to reduce HbA1c.