Walnut intake may increase circulating adiponectin and leptin levels but does not improve glycemic biomarkers: A systematic review and meta-analysis of randomized clinical trials

Effect of walnut consumption on markers of endothelial function in adults: A systematic review and meta-analysis of randomized controlled trials

Findings on the effect of walnut consumption on endothelial function are conflicting. Therefore, the present systematic review and meta-analysis summarized available trials in this regard. A systematic search was performed in online databases including PubMed-Medline, Scopus, and ISI Web of Science up to October 2023. Articles that reported the effect of walnut intake on flow-mediated dilation (FMD), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and stimulus-adjusted response measure (SARM) were included. Random effects models for a weighted mean difference (WMD) or standardized mean difference (SMD) were used to test for the overall effect. Six eligible trials were analyzed (250 participants). Walnut intake significantly increased FMD (WMD: 0.94%, 95% CI: 0.12 to 1.75; p = 0.02). However, meta-analysis could not show any beneficial effect of walnut intake on ICAM-1 (SMD: -0.23, 95% CI: -0.68 to 0.22; p = 0.31), VCAM-1 (SMD: -0.02, 95% CI: -1.38 to 1.34; p = 0.97), and SARM (WMD: 0.01%, 95% CI: -0.01 to 0.04; p = 0.28). In conclusion, the present meta-analysis suggests that walnuts may reduce cardiovascular disease risk by improving FMD. However, further studies should be performed on adults to determine the effect of walnut intake on endothelial function.

Plant-Based Dairy Alternatives-A Future Direction to the Milky Way

One significant food group that is part of our daily diet is the dairy group, and both research and industry are actively involved to meet the increasing requirement for plant-based dairy alternatives (PBDAs). The production tendency of PBDAs is growing with a predictable rate of over 18.5% in 2023 from 7.4% at the moment. A multitude of sources can be used for development such as cereals, pseudocereals, legumes, nuts, and seeds to obtain food products such as vegetal milk, cheese, cream, yogurt, butter, and different sweets, such as ice cream, which have nearly similar nutritional profiles to those of animal-origin products. Increased interest in PBDAs is manifested in groups with special dietary needs (e.g., lactose intolerant individuals, pregnant women, newborns, and the elderly) or with pathologies such as metabolic syndromes, dermatological diseases, and arthritis. In spite of the vast range of production perspectives, certain industrial challenges arise during development, such as processing and preservation technologies. This paper aims at providing an overview of the currently available PBDAs based on recent studies selected from the electronic databases PubMed, Web of Science Core Collection, and Scopus. We found 148 publications regarding PBDAs in correlation with their nutritional and technological aspects, together with the implications in terms of health. Therefore, this review focuses on the relationship between plant-based alternatives for dairy products and the human diet, from the raw material to the final products, including the industrial processes and health-related concerns.

Consumption of Nuts and Seeds and Health Outcomes Including Cardiovascular Disease, Diabetes and Metabolic Disease, Cancer, and Mortality: An Umbrella Review

Consumption of nuts and seeds is associated with a range of health outcomes. Summarizing the best evidence on essential health outcomes from the consumption of nuts is essential to provide optimal recommendations. Our objective is to comprehensively assess health outcome associations related to the consumption of nuts and seeds, using a culinary definition including tree nuts and peanuts (registered in PROSPERO: CRD42021258300). Health outcomes of interest include cardiovascular disease, cancer, diabetes, obesity, respiratory disease, mortality, and their disease biomarkers. We present associations for high compared with low consumption, per serving, and dose-response relations. MEDLINE, Embase, Cochrane, and Epistemonikos were searched and screened for systematic reviews and meta-analyses. Evidence was extracted from 89 articles on the consumption of nuts and relevant health outcomes, including 23 articles with meta-analysis on disease and mortality, 66 articles on biomarkers for disease, and 9 articles on allergy/adverse outcomes. Intake of nuts was associated with reduced risk of cardiovascular diseases and related risk factors, with moderate quality of evidence. An intake of 28 g/d nuts compared with not eating nuts was associated with a 21% RR reduction of cardiovascular disease (including coronary heart disease incidence and mortality, atrial fibrillation, and stroke mortality), an 11% risk reduction of cancer deaths, and 22% reduction in all-cause mortality. Nut consumption was also inversely associated with mortality from respiratory diseases, infectious diseases, and diabetes; however, associations between nut consumption and diabetes incidence were mixed. Meta-analyses of trials on biomarkers for disease generally mirrored meta-analyses from observational studies on cardiovascular disease, cancers, and diabetes. Allergy and related adverse reactions to nuts were observed in 1-2% of adult populations, with substantial heterogeneity between studies. Overall, the current evidence supports dietary recommendations to consume a handful of nuts and seeds per day for people without allergies to these foods.

Effect of nuts on components of metabolic syndrome in healthy adults with overweight/obesity: A systematic review and meta-analysis

AIMS

Randomized controlled trials evaluating the effects of nut consumption on the metabolic profile of healthy adults with overweight/obesity have yielded conflicting results. This systematic review and meta-analysis aimed to summarize the effects of incorporating nuts into the diet on serum lipid profile, glycemic markers, and blood pressure in healthy adults with overweight/obesity.

DATA SYNTHESIS

PubMed, Embase, Scopus, Web of Science, and Cochrane Library were searched up to April 2021. The random-effects model was used to determine the pooled effect sizes expressed as weighted mean difference (WMD) with % 95 confidence intervals (CIs). Ten eligible RCTs (with 12 arms) were included in the meta-analysis. The meta-analysis revealed that nut intake significantly decreased serum triglycerides (TG) (WMD: -13.19 mg/dL, 95% CI: - 25.90, - 0.48). Furthermore, subgroup analysis showed a significant reduction in serum LDL-cholesterol (LDL-C) following adherence to normocaloric, nut-enriched diets (WMD: - 4.56 mg/dL, 95% CI: - 8.24, - 0.88). However, nuts did not affect serum total cholesterol, high-density lipoprotein cholesterol, glycemic markers, and blood pressure.

CONCLUSIONS

Overall, incorporating nuts into the diet of healthy adults with overweight/obesity have favorable effects on serum TG and LDL-C. Thus, nuts might exert protective effects against dyslipidemia in this population.

REGISTRY NUMBER

PROPSPERO CRD42021250662.

Walnut consumption and health outcomes with public health relevance-a systematic review of cohort studies and randomized controlled trials published from 2017 to present

CONTEXT

Considering the accumulation of recent studies investigating the health effects of walnut consumption, both including and beyond cardiovascular health effects, a systematic review of this literature to investigate the strength of the evidence is warranted.

OBJECTIVE

To investigate associations between walnut consumption and outcomes with public health relevance (specifically all-cause mortality, type 2 diabetes, CVD, metabolic syndrome, obesity, cancer, neurological and mental health, musculoskeletal, gastrointestinal, and maternal disorders) and the effect on associated disease risk markers, reported in studies published from 2017 to present.

DATA SOURCES

MEDLINE, FSTA, CENTRAL, and Scopus were searched from 1 January 2017 to 5 May 2021.

DATA EXTRACTION

Human studies (cohort studies and RCTs) ≥3 weeks in duration comparing consumption of walnuts (whole, pieces, or 100% butter) to a control and measuring associations with relevant public health outcomes and disease risk markers were assessed. Key study characteristics were extracted independently by 2 investigators using a standardized table. The quality of the studies was assessed using the Cochrane Risk-of-Bias tool 2.0 and the Newcastle-Ottawa Scale.

DATA ANALYSIS

Only 1 RCT was considered to be at low risk of bias for any of its outcomes. The cohort studies were considered to be of moderate or high quality. The results were synthesized using vote counting, based on the direction of effect. Thirty-three articles, 23 describing RCTs (walnut dose ∼10-99 g/day, 1,948 subjects) and 10 describing cohort studies (∼675,928 subjects), were included. Vote counting could be performed for the blood lipids, cardiovascular function, inflammation- and hemostatic-related factors, markers of glucose metabolism, and body weight and composition outcome groupings. The results are presented in effect direction plots. With respect to blood lipids, results from 8/8 RCTs favoured walnuts, in accordance with associations with a reduced risk of CVD suggested by cohort studies; results from 6/6 RCTs favoured control with respect to body weight and composition, although most of these effects were small. This was contrary to cohort study results suggesting small benefits of walnut consumption on body weight. There was no overall consistent direction of effect for cardiovascular function, markers of glucose metabolism, or inflammation- and hemostatic-related factors.

CONCLUSIONS

Evidence published since 2017 is consistent with previous research suggesting that walnut consumption improves lipid profiles and is associated with reduced CVD risk. Evidence is accumulating in other areas, such as cognitive health, although more research is needed to draw firm conclusions.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD4202122.

Effects of Dietary α-Linolenic Acid Treatment and the Efficiency of Its Conversion to Eicosapentaenoic and Docosahexaenoic Acids in Obesity and Related Diseases

The essential fatty acid alpha-linolenic acid (ALA) is present in high amounts in oils such as flaxseed, soy, hemp, rapeseed, chia, and perilla, while stearidonic acid is abundant in echium oil. ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by desaturases and elongases in humans. The conversion of ALA to EPA and DHA is limited, and these long-chain n−3 polyunsaturated fatty acids (PUFAs) are mainly provided from dietary sources (fish and seafood). This review provides an overview of studies that explored the effects of dietary supplementation with ALA in obesity and related diseases. The obesity-associated changes of desaturase and elongase activities are summarized, as they could influence the metabolic conversion of ALA. Generally, supplementation with ALA or ALA-rich oils leads to an increase in EPA levels and has no effect on DHA or omega-3 index. According to the literature data, stearidonic acid could enhance conversion of ALA to long-chain n−3 PUFA in obesity. Recent studies confirm that EPA and DHA intake should be considered as a primary dietary treatment strategy for improving the omega-3 index in obesity and related diseases.

Nuts and Metabolic Syndrome: Reducing the Burden of Metabolic Syndrome in Menopause

Menopause imposes a dramatic fall in estrogens, which is followed by an increase in the proportion of fat. The rising androgen/estrogen ratio along the menopause transition favors the accumulation of central fat, which contributes to insulin resistance and a series of concatenated effects, leading to a higher incidence of metabolic syndrome. The modulatory effect of diet on the metabolic syndrome phenotype has been shown for the Mediterranean diet, and nuts are key determinants of these health benefits. This review of the impact of nuts on the risk factors of the metabolic syndrome cluster examined studies—prioritizing meta-analyses and systemic reviews—to summarize the potential benefits of nut ingestion on the risk of metabolic syndrome associated with menopause. Nuts have a general composition profile that includes macronutrients, with a high proportion of unsaturated fat, bioactive compounds, and fiber. The mechanisms set in motion by nuts have shown different levels of efficacy against the disturbances associated with metabolic syndrome, but a beneficial impact on lipids and carbohydrate metabolism, and a potential, but minimal reduction in blood pressure and fat accumulation have been found.

Impact of walnut consumption on cardio metabolic and anthropometric parameters in metabolic syndrome patients: GRADE-assessed systematic review and dose-response meta-analysis of data from randomized controlled trials

BACKGROUND

In recent years, the effect of walnut consumption on various components of metabolic syndrome (Mets) in different populations has been investigated. However, the findings on the alterations of cardiometabolic and anthropometric indices following walnut consumption in adults with Mets have not been fully conclusive.

METHODS

The current study of eight randomized controlled trials (RCTs) examined the effects of walnut consumption on glucose homeostasis factors (fasting plasma glucose (FPG), insulin, hemoglobin A1C (HbA1c)), lipid profile (triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c)), high sensitivity C-reactive protein (hs-CRP) concentrations and anthropometric indices (body weight (BW), body mass index (BMI), and waist circumference (WC)) in trials of 549 participants. A systematic search was conducted in online databases including MEDLINE, Scopus, and Clarivate Analytics Web of Science uses related keywords to detect eligible studies until December 2021. To calculate the weighted mean difference (WMD) and 95% confidence intervals (CIs), a random-effects model was used.

RESULTS

Results from the pooled analysis showed that serum TG concentration was significantly reduced (WMD, - 0.1 mmol/L; 95%CI (- 0.3 to - 0.02); p = 0.02; I2 = 38.6%; p = 0.10), although other lipid profile components (TC, LDL-c, and HDL-c), glucose homeostasis markers (FPG, insulin, and HbA1c), hs-CRP levels, anthropometric indices (BW, BMI, and WC) and blood pressure (SBP and DBP) were not influenced by walnut consumption. A significant dose-response association was detected between the dose of walnut intake and serum concentrations of FPG (Pnon-linearity < 0.03, Pdose-response < 0.001) and HDL-c (Pnon-linearity = 0.01, Pdose-response = 0.006).

CONCLUSIONS

Walnut consumption reduces serum TG levels in individuals with metabolic syndrome, but it cannot affect other cardiometabolic indices. Future well-designed and large RCTs are required to clarify further beneficial effects of walnut consumption on the cardiometabolic profile.

The Influence of Nutrition on Adiponectin-A Narrative Review

The adipose tissue is an active endocrine organ which synthesizes and secretes a variety of adipokines, including adiponectin with its anti-inflammatory properties. Its expression is influenced by numerous factors such as age, sex, body weight and adipose tissue content. However, dietary factors, i.e., diet structure and the percentage of individual nutrients and products, are very important modulators. Beneficial dietary habits are the Mediterranean diet, DASH diet, diet based on plant products and diet with reduced energy value. Moreover, the share of individual products and nutrients which increase the concentration of adiponectin is worth noting. This group may include monounsaturated fatty acids, polyunsaturated omega-3 fatty acids, dietary fiber, polyphenols, alcohol and milk products. Conversely, dietary ingredients which have a negative effect on the concentration of adiponectin are typical components of the Western diet: saturated fatty acids, trans fatty acids, monosaccharides and disaccharides, and red meat. Furthermore, a diet characterized by a high glycemic index such as a high-carbohydrate low-fat diet also seems to be unfavorable. Due to the fact that available knowledge should be systematized, this study aimed to summarize the most recent research on the influence of dietary factors on the concentration of adiponectin.

Beyond Fish Oil Supplementation: The Effects of Alternative Plant Sources of Omega-3 Polyunsaturated Fatty Acids upon Lipid Indexes and Cardiometabolic Biomarkers-An Overview

Cardiovascular diseases remain a global challenge, and lipid-associated biomarkers can predict cardiovascular events. Extensive research on cardiovascular benefits of omega-3 polyunsaturated fatty acids (n3-PUFAs) is geared towards fish oil supplementation and fish-rich diets. Nevertheless, vegetarianism and veganism are becoming more popular across all segments of society, due to reasons as varied as personal, ethical and religious values, individual preferences and environment-related principles, amongst others. Due to the essentiality of PUFAs, plant sources of n3-PUFAs warrant further consideration. In this review, we have critically appraised the efficacy of plant-derived n3-PUFAs from foodstuffs and supplements upon lipid profile and selected cardiometabolic markers. Walnuts and flaxseed are the most common plant sources of n3-PUFAs, mainly alpha-linolenic acid (ALA), and feature the strongest scientific rationale for applicability into clinical practice. Furthermore, walnuts and flaxseed are sources of fibre, potassium, magnesium, and non-essential substances, including polyphenols and sterols, which in conjunction are known to ameliorate cardiovascular metabolism. ALA levels in rapeseed and soybean oils are only slight when compared to flaxseed oil. Spirulina and Chlorella, biomasses of cyanobacteria and green algae, are important sources of n3-PUFAs; however, their benefits upon cardiometabolic markers are plausibly driven by their antioxidant potential combined with their n3-PUFA content. In humans, ALA is not sufficiently bioconverted into eicosapentaenoic and docosahexaenoic acids. However, evidence suggests that plant sources of ALA are associated with favourable cardiometabolic status. ALA supplementation, or increased consumption of ALA-rich foodstuffs, combined with reduced omega-6 (n6) PUFAs intake, could improve the n3/n6 ratio and improve cardiometabolic and lipid profile.