Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke, and diabetes: a systematic review and meta-analysis

Abstract

Background: Relations between the consumption of nuts and legumes and risk of ischemic heart disease (IHD), stroke, and diabetes have not been well established.

Objective: We systematically investigated and quantified associations of nut and legume consumption with incident IHD, stroke, and diabetes.

Design: We systematically searched multiple databases to identify randomized controlled trials or observational studies that examined the relations. Studies were excluded if they reported only intermediate physiologic measures, soft cardiovascular outcomes, or crude risk estimates. Data were extracted independently and in duplicate. We assessed pooled dose-response relations by using a generalized least-squares trend estimation, and prespecified sources of heterogeneity were assessed by using metaregression. The potential for publication bias was explored by using funnel plots, Begg's and Egger's tests, and Duval and Tweedie trim-and-fill methods.

Results: Of 3851 abstracts, 25 observational studies (23 prospective and 2 retrospective studies) and 2 trial reports met inclusion criteria and comprised 501,791 unique individuals and 11,869 IHD, 8244 stroke, and 14,449 diabetes events. The consumption of nuts was inversely associated with fatal IHD (6 studies; 6749 events; RR per 4 weekly 28.4-g servings: 0.76; 95% CI: 0.69, 0.84; I(2) = 28%), nonfatal IHD (4 studies; 2101 events; RR: 0.78; 0.67, 0.92; I(2) = 0%), and diabetes (6 studies; 13,308 events; RR: 0.87; 0.81,0.94; I(2) = 22%) but not stroke (4 studies; 5544 events). Legume consumption was inversely associated with total IHD (5 studies; 6514 events; RR per 4 weekly 100-g servings: 0.86; 0.78, 0.94; I(2) = 0%) but not significantly associated with stroke (6 studies; 6690 events) or diabetes (2 studies; 2746 events). A meta-regression did not identify the effect modification by age, duration of follow-up, study location, or study quality. Mixed evidence was seen for publication bias, but analyses by using the Duval and Tweedie trim-and-fill method did not appreciably alter results.

Conclusion: This systematic review supports inverse associations between eating nuts and incident IHD and diabetes and eating legumes and incident IHD.

FIGURE 1.

Screening and selection process of studies evaluating the consumption of nuts or legumes and incidence of ischemic heart disease, stroke, or diabetes. CVD, cardiovascular disease.

FIGURE 2.

Nut consumption and risk of cardiometabolic endpoints. Nut intake and risk of fatal IHD (A), nonfatal IHD (B), stroke (C), and diabetes (D). The figure shows pooled estimates (dashed line) and 95% CIs (open diamond) of risk per 4 weekly servings (28.4 g) of nuts (left) and plots of pooled (solid black lines) and study-specific (solid gray lines) RRs (right). AHS, The Adventist Health Study; CHD, coronary heart disease; FMCHES, Finnish Mobile Clinic Health Examination Survey; HPFS, Health Professionals Follow-Up Study; IHD, ischemic heart disase; IWHS, Iowa Women's Health Study; NHS, Nurses’ Health Study; PHS, Physicians’ Health Study; PREDIMED, Prevencion con Dieta Mediterranea; ref, reference; SWHS, Shanghai Women's Health Study.

FIGURE 3.

Legume intake and risk of cardiometabolic endpoints. Legume intake and risk of total IHD (A), stroke (B), and diabetes (C). In each panel, the left figure shows the pooled estimates (dashed line) and 95% CIs (open diamond) of the risk per 4 weekly servings (100 g) of legumes, and the right figure shows the plot of the pooled (solid black line) and study-specific (solid gray lines) RRs. EPIC-G, European Prospective Investigation into Cancer and Nutrition-Greece; EPICH, European Prospective Investigation into Cancer and Nutrition-Heart; FMCHES, Finnish Mobile Clinic Health Examination Survey; HPFS, Health Professionals Follow-Up Study; IHD, ischemic heart disease; IWHS, Iowa Women's Health Study; JACC, Japan Collaborative Cohort Study; JPHC, The Japan Public Health Center–Based Study; NHEFS, NHANES Epidemiologic Follow-up Study; NHS, Nurses’ Health Study; ref, reference; SWHS, Shanghai Women's Health Study.