Archive

Research Area: Cardiovascular Health

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

Lockyer, S., A.E. de la Hunty, S. Steenson, A. Spiro, S.A. Stanner, 2022. Walnut consumption and health outcomes with public health relevance-a systematic review of cohort studies and randomized controlled trials published from 2017 to present. Nutr. Rev. 81(1):26–54. https://doi.org/10.1093/nutrit/nuac040

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.

Circulating linoleic acid at the time of myocardial infarction and risk of primary ventricular fibrillation.

Oliveras, T., I. Lázaro, F. Rueda, G. Cediel, D.L. Bhatt, M. Fitó, F. Madrid-Gambin, O.J. Pozo, W.S. Harris, C. García-García, A. Sala-Vila, A. Bayés-Genís, 2022. Circulating linoleic acid at the time of myocardial infarction and risk of primary ventricular fibrillation. Sci. Rep. 12(1):4377. https://doi.org/10.1038/s41598-022-08453-0

Primary ventricular fibrillation (PVF) is a major driver of cardiac arrest in the acute phase of ST-segment elevation myocardial infarction (STEMI). Enrichment of cardiomyocyte plasma membranes with dietary polyunsaturated fatty acids (PUFA) reduces vulnerability to PVF experimentally, but clinical data are scarce. PUFA status in serum phospholipids is a valid surrogate biomarker of PUFA status in cardiomyocytes within a wide range of dietary PUFA. In this nested case-control study (n = 58 cases of STEMI-driven PVF, n = 116 control non-PVF STEMI patients matched for age, sex, smoking status, dyslipidemia, diabetes mellitus and hypertension) we determined fatty acids in serum phospholipids by gas-chromatography, and assessed differences between cases and controls, applying the Benjamini-Hochberg procedure on nominal P-values to control the false discovery rate (FDR). Significant differences between cases and controls were restricted to linoleic acid (LA), with PVF patients showing a lower level (nominal P = 0.002; FDR-corrected P = 0.027). In a conditional logistic regression model, each one standard deviation increase in the proportion of LA was related to a 42% lower prevalence of PVF (odds ratio = 0.58; 95% confidence interval, 0.37, 0.90; P = 0.02). The association lasted after the inclusion of confounders. Thus, regular consumption of LA-rich foods (nuts, oils from seeds) may protect against ischemia-driven malignant arrhythmias.

Key Area: Heart Health

Impact of α-linolenic acid, the vegetable ω-3 fatty acid, on cardiovascular disease and cognition.

Sala-Vila, A., J. Fleming, P. Kris-Etherton, E. Ros, 2022. Impact of α-linolenic acid, the vegetable ω-3 fatty acid, on cardiovascular disease and cognition. Adv. Nutr. 13(5):1584–1602. https://doi.org/10.1093/advances/nmac016

Given the evidence of the health benefits of plant-based diets and long-chain n-3 fatty acids, there is keen interest in better understanding the role of alpha-linolenic acid (ALA), a plant-derived n-3 fatty acid, on cardiometabolic diseases and cognition. There is increasing evidence for ALA largely based on its major food sources (i.e., walnuts and flaxseed); however, this lags behind our understanding of long-chain n-3 fatty acids. Meta-analyses of observational studies have shown that increasing dietary ALA is associated with a 10% lower risk of total cardiovascular disease and a 20% reduced risk of fatal coronary heart disease. Three randomized controlled trials (Alpha Omega trial, Prevención con Dieta Mediterránea [PREDIMED] trial, and Lyon Diet Heart Study) all showed benefits of diets high in ALA on cardiovascular-related outcomes, but the Alpha Omega trial, designed to specifically evaluate ALA effects, only showed a trend for benefit. Randomized controlled trials have shown that dietary ALA reduced total cholesterol, low-density-lipoprotein cholesterol, triglycerides, and blood pressure, and epidemiological studies and some trials also have shown an anti-inflammatory effect of ALA; which collectively account for, in part, the cardiovascular benefits of ALA. A meta-analysis reported a trend toward diabetes risk reduction with both dietary and biomarker ALA. For metabolic syndrome and obesity, the evidence for ALA benefits is inconclusive. The role of ALA in cognition is in the early stages but shows promising evidence of counteracting cognitive impairment. Much has been learned about the health benefits of ALA and with additional research we will be better positioned to make strong evidence-based dietary recommendations for the reduction of many chronic diseases.

Association of nut consumption with CVD risk factors in young to middle-aged adults: The Coronary Artery Risk Development in Young Adults (CARDIA) study. 

Yi, S.Y., L.M. Steffen, X. Zhou, J.M. Shikany, D.R., Jr. Jacobs, 2022. Association of nut consumption with CVD risk factors in young to middle-aged adults: The Coronary Artery Risk Development in Young Adults (CARDIA) study. Nutr Metab Cardiovasc Dis. 32(10):2321–2329. https://doi.org/10.1016/j.numecd.2022.07.013

Background and Aims: Few studies have examined long-term associations of walnut, other nut, and no nut consumption with cardiovascular disease (CVD) risk factors. Results from prospective studies with long-term follow-up can provide further evidence for dietary guideline messaging to consume nuts. Therefore, we examined the associations of walnut, other nut, and no nut consumption with diet quality and CVD risk factors over 30 years of follow-up. Methods and Results: Data were analyzed from 3,092 young adults enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Dietary intake, including walnuts and other nuts, was assessed 3 times over 20 years. CVD risk factors were measured at multiple exams. General linear regression evaluated the associations of walnut, other nut, and no nut consumption with CVD risk factors over 30 years (Y30) of follow-up. The 20-year cumulative mean intake of walnuts (0.74 oz/d), other nuts (1.6 oz/d), or no nut consumption was differentially associated with HEI-2015 and CVD risk factors by Y30. Generally, walnut consumers had significantly higher HEI-2015, lower body mass index, waist circumference, blood pressure, and triglyceride concentration, and gained less weight since baseline than other nut consumers (p ≤0.05 for all). Further, walnut consumers had lower fasting blood glucose than no nut consumers (p ≤0.05). Conclusion: Study findings that walnut and other nut consumption was associated with better CVD risk factors and diet quality aligns with the 2020-2025 U.S. Dietary Guidelines for Americans recommendation to consume nuts, such as walnuts, within the context of a healthy diet.