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In the largest study of its kind, people who ate a daily handful of nuts were 20 percent less likely to die from any cause over a 30-year period than those who didn't consume nuts, say researchers from Dana-Farber Cancer Institute, BWH and the Harvard School of Public Health.
The report, published in The New England Journal of Medicine, contains further good news: Regular nut-eaters were found to weigh less than those who didn't eat nuts, a finding that may alleviate a common concern that eating a lot of nuts-which are typically dense in calories-will lead to gaining weight.
"The most obvious benefit was a reduction of 29 percent in deaths from heart disease-the major killer of people in the U.S.," said senior author Charles Fuchs, MD, MPH, director of the Gastrointestinal Cancer Center at Dana-Farber, who is also affiliated with BWH's Channing Division of Network Medicine. "But we also saw a significant reduction (11 percent) in the risk of dying from cancer."
Whether any specific type or types of nuts were crucial to the protective effect couldn't be determined. However, the reduction in mortality was similar both for peanuts and for tree nuts (walnuts, hazelnuts, almonds and cashews, to name a few).
Previous studies have found an association between increasing nut consumption and a lower risk of diseases such as heart disease, type 2 diabetes and colon cancer. Higher nut consumption also has been linked to reductions in cholesterol levels, inflammation and insulin resistance. But no prior studies had looked in such detail at various levels of nut consumption and their effects on overall mortality in a large population followed for a significant period of time.
Researchers tapped into databases from two well-known studies: the Nurses' Health Study, which provided data on 76,464 women from 1980 to 2010, and the Health Professionals' Follow-up Study, which yielded data on 42,498 men from 1986 to 2010. Participants regularly filled out detailed food questionnaires, including how often they ate one ounce of nuts.
"In all analyses, the more nuts people ate, the less likely they were to die over the 30-year follow-up period," said Ying Bao, MD, ScD, also of BWH's Channing Division of Network Medicine, and first author of the report.
Those who ate nuts less than once a week had a 7 percent reduction in mortality; once a week, an 11 percent reduction; two to four times per week, a 13 percent reduction; five to six times per week, a 15 percent reduction, and seven or more times a week, a 20 percent reduction in death rate.
Though the authors note this does not prove cause and effect, the findings are strongly consistent with a wealth of existing data supporting nuts' health benefits.