Eating more nuts correlated with significantly lower mortality, both overall and for cancer, heart disease, and lung disease, according to data from follow-up in two large cohort studies.
As the frequency of nut consumption increased, the mortality hazard decreased by 7% with weekly intake to 20% for daily nut consumption, as compared with people who did not eat nuts.
The benefits pertained to any type of nut consumption, not specific nuts, Charles S. Fuchs, MD, of Dana-Farber Cancer Institute in Boston, and co-authors reported online in the New England Journal of Medicine.
"We did look at subtypes of nuts, but I can tell you that we really don't see a difference between the various nut types," Fuchs told MedPage Today. "So, peanuts as opposed to other nuts seemed to confer the same benefit in reducing mortality."
Nuts have a high nutrient density and a high concentration of unsaturated fatty acids. Observational studies have linked nut consumption to beneficial effects related to coronary heart disease and certain heart disease risk factors.
As a result of the evidence, the FDA in 2003 recommended consumption of 1.5 ounces of nuts daily as part of a low-fat diet that "may reduce the risk of heart disease."
More recently, a randomized trial of primary prevention in patients with a high cardiovascular risk showed that a nut-containing Mediterranean diet was associated with a significantly lower risk of cardiovascular events, as compared with patients assigned to a control diet.
Multiple observational and interventional studies have demonstrated favorable effects of nut consumption on various diseases (diabetes, colon cancer, gallstones) and in recognized mediators of chronic disease (oxidative stress, inflammation).
The accumulation of data has included minimal evidence that nut consumption reduces total mortality, the authors noted in their introduction. Additionally, the studies have been limited by small sample size, limited dietary information, and lack of adequate adjustment for confounders.
To examine the relationship of nut consumption to mortality, investigators analyzed data from 76,464 women who participated in the Nurses' Health Study and from 42,498 men in the Health Professionals Follow-up Study. Both studies accumulated data from multiple follow-up visits and questionnaires over 20 to 24 years.
The final analysis comprised 3,038,853 person-years of follow-up, during which time 16,200 women and 11,229 men died. Comparison of the two studies showed no significant heterogeneity, so investigators combined the results into a single analysis.
As compared with study participants who reported no consumption, the mortality hazard declined significantly (P<0.001 for trend) as weekly nut consumption increased:
- Less than once -- HR 0.93, 95% CI 0.90-0.93
- Once -- HR 0.89, 95% CI 0.86-0.93
- Two to four times -- HR 0.87, 95% CI 0.83-0.90
- Five or six times -- HR 0.85, 95% CI 0.79-0.91
- Seven or more -- HR 0.80, 95% CI 0.73-0.86
Subgroup analysis showed no difference in benefit among peanuts, tree nuts, and other types of nuts with respect to all-cause mortality or death from heart or respiratory disease or cancer.
Commenting on possible concerns about the fat and calories in nuts, Fuchs said the evidence still supports regular nut consumption.
"We really don't see a problem with it," he said. "In fact, one might argue that nuts are probably a very good source of calories, namely, calories that don't seem to contribute to obesity."
