Nuts and seeds consumption and risk of cardiovascular disease, type 2 diabetes and their risk factors: a systematic review and meta-analysis

Abstract

Objectives: We aimed to systematically review studies and evaluate the strength of the evidence on nuts/seeds consumption and cardiometabolic diseases and their risk factors among adults.
 Methods: A protocol was pre-registered in PROSPERO (CRD42021270554). We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Scopus up to September 20, 2021 for prospective cohort studies and ≥12-week randomized controlled trials (RCTs). Main outcomes were cardiovascular disease (CVD), coronary heart disease (CHD), stroke and type 2 diabetes (T2D), secondary total-/low density lipoprotein (LDL)-cholesterol, blood pressure and glycaemic markers. Data extraction and risk of bias (RoB) assessments (using RoB 2.0 and RoB-NObS) were performed in duplicate. Effect sizes were pooled using random-effects meta-analyses and expressed as relative risk (RR) or weighted mean differences with 95% confidence intervals (CI); heterogeneity quantified as I2. One-stage dose-response analyses assessed the linear and non-linear associations with CVD, CHD, stroke and T2D. The strength of evidence was classified per the World Cancer Research Fund criteria.
 Results: After screening 23,244 references, we included 42 papers from cohort studies (28 unique cohorts, 1,890,573 participants) and 18 RCTs (2,266 participants). In the cohorts, mainly populations with low consumption, high versus low total nuts/seeds consumption was inversely associated with total CVD (RR 0.81; 95% CI 0.75, 0.86; I2 = 67%), CVD mortality (0.77; 0.72, 0.82; I2 = 59.3%), CHD (0.82; 0.76, 0.89; I2 = 64%), CHD mortality (0.75; 0.65, 0.87; I2 = 66.9%) and non-fatal CHD (0.85; 0.75, 0.96; I2 = 62.2%). According to the non-linear dose-response analyses, consumption of 30 g/day of total nuts/seeds was associated with RRs of similar magnitude. For stroke and T2D the summary RR for high versus low intake was 0.91 (95% CI 0.85, 0.97; I2 = 24.8%) and 0.95 (0.75, 1.21; I2 = 82.2%). Intake of nuts (median ~50 g/day) lowered total (−0.15 mmol/L; −0.22, −0.08; I2 = 31.2%) and LDL-cholesterol (−0.13 mmol/L; −0.21, −0.05; I2 = 68.6%), but not blood pressure. Findings on fasting glucose, HbA1c and insulin resistance were conflicting. The results were robust to sensitivity and subgroup analyses. We rated the associations between nuts/seeds and both CVD and CHD as probable. There was limited but suggestive evidence for no association with stroke. No conclusion could be made for T2D.
 Conclusion: There is a probable relationship between consumption of nuts/seeds and lower risk of CVD, mostly driven by CHD, possibly in part through effects on blood lipids. More research on stroke and T2D may affect the conclusions. The evidence of specific nuts should be further investigated.

Underrated aspects of a true Mediterranean diet: understanding traditional features for worldwide application of a “Planeterranean” diet

“…The health benefits of nuts and seeds are well documented in the scientific literature [ 148 ]. Consistent results are showing an association between nut consumption and lower risk of CVD in a dose-dependent manner, while smaller or unclear associations with risk of stroke and type 2 diabetes have been reported [ 149 ]. Moreover, findings from randomized controlled trials administering nuts as intervention arm confirm their potential effects on total and low-density lipoprotein cholesterol [ 149 ].…”

“…Consistent results are showing an association between nut consumption and lower risk of CVD in a dose-dependent manner, while smaller or unclear associations with risk of stroke and type 2 diabetes have been reported [ 149 ]. Moreover, findings from randomized controlled trials administering nuts as intervention arm confirm their potential effects on total and low-density lipoprotein cholesterol [ 149 ]. Concerning seeds, only a minority of studies have been conducted on commercial products, such as sesame [ 150 , 151 ], fenugreek [ 152 ], and flaxseeds [ 153 , 154 ] reporting significant effects of markers of inflammation and CVD risk factors, albeit not with univocal result [ 155 – 157 ].…”

Effect of Aqueous Extract of Irvingia wombolu Seeds on Lipid Profile and Atherogenic Indices in Hyperlipidemic Wistar Rats

“…Hyperlipidemia is a disorder of lipid metabolism that results in an elevated level of circulating cholesterol and/or triglycerides, also known as triacylglycerols (TG) [1]; [2]. It is the most prevalent form of dyslipidemia.…”

“…Dyslipidemia usually involve elevated plasma levels of triglycerides (TG), total cholesterol, low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesteroland a low level of high density lipoprotein (HDL) cholesterol [1]; [3]. This disorder is associated with the development of atherosclerosis, particularly coronary heart disease (CHD), stroke, peripheral vascular disease, which are the major cardiovascular diseases (CVD) [2]. nuts and seeds forms important parts of healthy dietary patterns and eating plans such as the healthy Nordic diet, the Dietary Approaches to Stop Hypertension (DASH) [2].…”

“…This disorder is associated with the development of atherosclerosis, particularly coronary heart disease (CHD), stroke, peripheral vascular disease, which are the major cardiovascular diseases (CVD) [2]. nuts and seeds forms important parts of healthy dietary patterns and eating plans such as the healthy Nordic diet, the Dietary Approaches to Stop Hypertension (DASH) [2]. Interest in nuts for prevention of cardiometabolic disease emerged in 1992 after Fraser et al [4] reported a lower risk of fatal coronary heart disease (CHD) and myocardial infarction (MI) among frequent nut consumers (>4 servings per week) in the Adventist Health Study [4].…”