*2.1. Nut Consumption in Cardiometabolic Morbidity and Mortality*

Clinical trials and lengthy prospective studies, focusing on men and women over the age of 55, showed that higher weekly nut intake can lower all causes and cause-specific morbidity and mortality [13–21] (Table 1).

Subjects at high cardiovascular (CV) risk, who supplemented their MD with 30 grams of tree nuts per day, at any point in time during the 4 years study period, had a 53% lower diabetes incidence compared to the control group [13]. Pan et al. [14] observed that women in the highest nut serving group were 26% less likely to develop diabetes than participants in the very low nut intake group, with 95% confidence that the true value is lying between 16%–35%. Similarly, when comparing high to very low nut intake, the prevalence of diabetes, obesity, and MS were 13%, 39%, and 26% less likely, respectively [15].

A single meta-analysis [22] confirmed that subjects in the highest total nut intake group had 32% less risk of dying from diabetes than those in the lowest group (relative risk, RR = 0.68, 95% confidence interval, CI: 0.52–0.90).


Nut consumption and cardiometabolic morbidity and mortality.

**Table 1.**



\* CV—cardiovascular; CVD—cardiovascular diseases; F—women; H—hazelnuts; HR—hazard ratio; HPFS—Health Professionals Follow-Up Study; M—men; MD—Mediterranean diet; MS—metabolic syndrome; NHS—Nurses' Health Study; OR—odds ratio; RCT—randomized controlled trial; RR—risk ratio; T2DM—type 2 diabetes mellitus; W—walnuts.

One prospective study showed a nonsignificant reduction in cardiovascular disease (CVD) mortality when comparing the highest with the lowest nut intake population groups [17]. However, two others concluded that participants who were fed nut-enhanced MDs had a significantly lower risk for CVD and CHD, as well as lower CVD, CHD, and all-cause mortality compared to the no-nut group [16,18]. Participants who consumed walnuts ≥1 serving per week had 19%, 21%, and 17% lower risk for CVD, CHD, and stroke, respectively, while those who consumed walnuts >3 servings per week had 47% lower risk of CV mortality compared with subjects who did not eat walnuts [18]. A very recent prospective study demonstrated lower CVD incidence (hazard ratio, HR = 0.83, 95% CI: 0.71–0.98) and CHD incidence (HR = 0.80, 95% CI: 0.67–0.96), 31% lower all-cause mortality and 34% lower CVD mortality for at least 5 servings of nuts per week compared to less than one per month [21]. In the same study, total nut intake was not significantly associated with stroke incidence. Moreover, a recent intervention study showed that individuals at high CV risk had a lower incidence of major CV events (myocardial infarction, stroke, death from CV causes) when nuts were added daily to MD compared with a low-fat, nut-free control diet [20]. Also, three or more servings of nuts per week, as compared to none, can even lower the risk of atrial fibrillation and heart failure [19].

Peripheral arterial disease (PAD), often caused by atherosclerosis, can lead to heart attack and stroke. A large cross-sectional study on mature adults indicated that daily nut consumption was associated with lower odds of PAD (OR = 0.79; 95% CI: 0.77–0.80, *p* < 0.001) compared to participants with the lowest intake of nuts [23].

A very recent meta-analysis of 11 observational studies confirmed that tree nut (but not peanut) consumption was negatively associated with metabolic syndrome (MS) (*p* = 0.04) [24]. Another meta-analysis showed a significantly reduced risk for CVD and CHD for higher nut consumption (including peanuts) [22]. Luu et al. [24] showed that in different ethnic groups, nut consumption was associated with decreased overall mortality and CVD mortality and that a higher versus lower quintile of nut intake had a statistically significant inverse association for ischemic heart disease (IHD). Mayhew et al. [25], after reviewing several large prospective cohort studies, concluded that nut consumption was inversely associated with total CVD, CVD mortality, total CHD, CHD mortality, and sudden cardiac death. While one meta-analysis established that daily nut intake can reduce the risk of stroke [26], another study did not find a significant association with stroke, but indicated an inverse association with IHD, overall CVD, and all-cause mortality for nut consumption [27]. A meta-analysis of randomized controlled trials (RCTs) and observational studies identified that nut feeding was inversely linked with nonfatal and fatal IHD and diabetes, but not stroke [28]. However, a meta-analysis of prospective cohorts to evaluate the relation between nuts and stroke risk and mortality, reported that nut consumption was inversely associated with stroke risk (RR 0.90, 95% CI: 0.83–0.98) and stroke mortality, when comparing the highest with the lowest nut intake [29].

High blood pressure (BP) is a major risk factor for CVD. The previous feeding studies showed that tree nuts or peanuts had no effect on BP. However, a very recent RCT on an elderly cohort (age, 69 years) proved that walnuts (42.5 grams per day) reduced systolic BP in the walnut group (−4.61 mm Hg, 95% CI: −7.43 to −1.79 mm Hg) compared to the no-walnut group (−0.59 mm Hg, 95% CI: −3.38 to 2.21 mm Hg) (*p* = 0.051) [30]. As no changes in diastolic BP were noticed, it is safe to say that walnut intake can reduce systolic BP in mature subjects, mainly in those with mild hypertension.
