Eating nuts linked to longer life and lower risk of diseases

21 November 2013

A study tracking the diet of over 100,000 men and women over 30 years has found that people who ate a daily handful of nuts were 20% percent less likely to die from any cause than were those who didn’t consume nuts. In addition, the nut eaters were slimmer than those who didn't eat nuts.

The study by the Dana-Farber Cancer Institute, Brigham and Women’s Hospital, and the Harvard School of Public Health has been published in the New England Journal of Medicine, contains further good news.

The reduction in mortality was similar both for peanuts and for 'tree nuts' — walnuts, hazelnuts, almonds, Brazil nuts, cashews, macadamias, pecans, cashews, pistachios and pine nuts.

Data analysis methods were used to rule out other dietary and lifestyle factors that might have accounted for the mortality benefits. For example, the researchers found that individuals who ate more nuts were leaner, less likely to smoke, and more likely to exercise, use multivitamin supplements, consume more fruits and vegetables, and drink more alcohol. However, the analysis was able to isolate the association between nuts and mortality independently of these other factors.

Several previous studies have found an association between increasing nut consumption and a lower risk of diseases such as heart disease, type 2 diabetes, colon cancer, gallstones, and diverticulitis. Higher nut consumption also has been linked to reductions in cholesterol levels, oxidative stress, inflammation, adiposity, and insulin resistance.

Some small studies have linked increased nuts in the diet to lower total mortality in specific populations. But no previous research studies had looked in such detail at various levels of nut consumption and their effects on overall mortality in a large population that was followed for over 30 years.

“The most obvious benefit was a reduction of 29% in deaths from heart disease — the major killer of people in America,” said Charles S. Fuchs, MD, MPH, director of the Gastrointestinal Cancer Center at Dana-Farber, who is the senior author of the report. “But we also saw a significant reduction — 11% — in the risk of dying from cancer,” added Fuchs, who is also affiliated with the Channing Division of Network Medicine at Brigham and Women’s.

“In all these analyses, the more nuts people ate, the less likely they were to die over the 30-year follow-up period,” explained Ying Bao, MD, ScD, of Brigham and Women’s Hospital, first author of the report. Those who ate nuts less than once a week had a 7% reduction in mortality; once a week, 11% reduction; two to four times per week, 13% reduction; five to six times per week, 15% reduction, and seven or more times a week, a 20% reduction in death rate.

The authors do note that this large study cannot definitively prove cause and effect; nonetheless, the findings are strongly consistent with “a wealth of existing observational and clinical trial data to support health benefits of nut consumption on many chronic diseases.” In fact, based on previous studies, the US Food and Drug Administration concluded in 2003 that eating 1.5 ounces per day of most nuts “may reduce the risk of heart disease.”

The study used databases from two well-known ongoing observational studies that collect data on diet and other lifestyle factors and various health outcomes. The Nurses’ Health Study provided data on 76,464 women between 1980 and 2010, and the Health Professionals’ Follow-up Study yielded data on 42,498 men from 1986 to 2010.

Participants in the studies filled out detailed food questionnaires every two to four years. With each food questionnaire, participants were asked to estimate how often they consumed nuts in a serving size of one ounce.