People who regularly eat nuts have a reduced risk of cardiovascular disease (CVD) and coronary heart disease (CHD) when compared to people who rarely or never eat nuts, according to a study published Nov. 13 in the Journal of the American College of Cardiology.

The study encompassed more than 210,000 people, including women from the Nurses’ Health Study and Nurses’ Health Study II and men from the Health Professionals Follow-up Study. In all three cohorts, information about medical history, lifestyle and health conditions was obtained every two years via self-administered questionnaires.

After up to 32 years of follow-up, the researchers assessed the associations of total nut intake and the consumption of individual nuts with CVD, CHD and stroke risk. CVD and CHD included a combination of MI and stroke, but CVD also included all forms of cardiovascular-related death.

Lead researcher Marta Guasch-Ferre, PhD, from the Harvard T.H. Chan School of Public Health, and colleagues reported the following findings:

• People who ate one 28-gram serving of nuts at least five times a week cut the risk of cardiovascular disease (CVD) by 14 percent and the risk of coronary heart disease (CHD) by 20 percent when compared to people who rarely or never consumed nuts.
• Each per-week serving increase of nuts was associated with a 6 percent reduced risk of CVD and a 13 percent reduced risk of CHD.
• Consuming one serving of walnuts per week was linked to a 19 percent lower risk of CVD and a 21 percent lower risk of CHD.
• Consuming two or more servings of peanuts or tree nuts per week was associated with risk reductions of 13 and 15 percent, respectively, for CVD; and 15 and 23 percent, respectively, for CHD.
• Walnut intake was associated with a 17 percent lower risk of stroke, while peanut butter and tree nuts were not linked to stroke risk. There were not significant ties between total nut consumption and stroke risk.

Peanuts are legumes, but the researchers included them in the study because peanuts have similar nutrient profiles as nuts.

“Nuts are high in unsaturated fatty acids, dietary fiber, minerals, vitamins, and several bioactive compounds, which may in part explain their beneficial effects on cardiovascular health,” Guasch-Ferre et al. wrote. “Randomized controlled trials have shown that consumption of nuts improves lipid profiles, attenuates inflammation, oxidative stress, improves endothelial function, and decreases insulin resistance. Nuts are also rich in polymerized polyphenols, which provide a substrate for gut microbiota.”

Despite being energy-dense, the researchers noted, nuts have been linked to decreased obesity risk, likely because they make snackers feel full and therefore less likely to opt for an unhealthy alternative.

One limitation of the study is that it only included white health professionals, but the authors pointed out there is no reason to believe the findings would be different when applied to men and women of different ethnicities. In addition, the self-reports of nut intake may have been subject to recall bias, and the researchers weren’t able to study the effects of different ways in which the nuts were prepared for consumption.

In a related editorial, Emilio Ros, MD, PhD, offered an explanation for why walnuts may have had the greatest protective effect against CVD, CHD and stroke compared to other nuts.

“The fact that sparingly consuming walnuts is associated with lower CVD and CHD rates to a similar extent than frequent consumption of total nuts, while also reducing stroke risk, suggests a stronger antiatherogenic effect of walnuts,” he wrote. “This may reflect their unique richness in α-linolenic acid and the fact that they are usually consumed raw, hence they keep the outer skin, whereas most other nuts are consumed roasted and lose the peel in which most antioxidants reside.”

Roos added peanut butter may not have performed as well as the other foods studied because it is typically processed with additional salt, honey or sugar.

“Ideally, further investigations should test the effects of long-term consumption of nuts supplemented in the usual diet on hard cardiometabolic events,” Roos wrote. “In the meantime, raw nuts, if possible unpeeled and otherwise unprocessed, may be considered as natural health capsules that can be easily incorporated into any heart-protective diet to further cardiovascular well-being and promote healthy aging.”