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Large study links nut consumption to reduced death rate

Date: [2014-01-06]  Author:   From: 

In the largest study of itskind, people who ate a daily handful of nuts were 20 percent less likely to diefrom any cause over a 30-year period than were those who didn’t consume nuts,say scientists from Dana-Farber Cancer Institute, Brigham and Women’s Hospital,and the Harvard School of Public Health.

Their report, published in theNew England Journal of Medicine, contains further good news. The regularnut-eaters were found to be more slender than those who didn’t eat nuts, afinding that should alleviate the widespread worry that eating a lot of nutswill lead to overweight.

The report also looked at theprotective effect on specific causes of death.

“The most obvious benefit wasa reduction of 29 percent in deaths from heart disease – the major killer ofpeople in America,” said Charles S.Fuchs, MD, MPH, director of the GastrointestinalCancer Treatment Center at Dana-Farber, who is the senior author ofthe report. “But we also saw a significant reduction – 11 percent – in the riskof dying from cancer,” added Fuchs, who is also affiliated with the ChanningDivision of Network Medicine at Brigham and Women’s.

Whether any specific type ortypes of nuts were crucial to the protective effect couldn’t be determined.However, the reduction in mortality was similar both for peanuts and for “treenuts” – walnuts, hazelnuts, almonds, Brazil nuts, cashews, macadamias, pecans,pistachios and pine nuts.

Several previous studies havefound an association between increasing nut consumption and a lower risk ofdiseases such as heart disease, type 2 diabetes, colon cancer, gallstones, anddiverticulitis. Higher nut consumption also has been linked to reductions incholesterol levels, oxidative stress, inflammation, adiposity, and insulinresistance. Some small studies have linked increased nuts in the diet to lowertotal mortality in specific populations. But no previous research studies hadlooked in such detail at various levels of nut consumption and their effects onoverall mortality in a large population that was followed for over 30 years.

For the new research, thescientists were able to tap databases from two well-known ongoing observationalstudies that collect data on diet and other lifestyle factors and varioushealth outcomes. The Nurses’ Health Study provided data on 76,464 women between1980 and 2010, and the Health Professionals’ Follow-up Study yielded data on42,498 men from 1986 to 2010. Participants in the studies filled out detailedfood questionnaires every two to four years. With each food questionnaire,participants were asked to estimate how often they consumed nuts in a servingsize of one ounce. A typical small packet of peanuts from a vending machinecontains one ounce.

Sophisticated data analysismethods were used to rule out other factors that might have accounted for themortality benefits. For example, the researchers found that individuals who atemore nuts were leaner, less likely to smoke, and more likely to exercise, usemultivitamin supplements, consume more fruits and vegetables, and drink morealcohol. However, analysis was able to isolate the association between nuts andmortality independently of these other factors.

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

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

The study is supported byNational Institutes of Health grants UM1 CA167552, P01 CA87969, R01 HL60712,R01CA124908, P50 CA127003, and 1U54 CA155626-01, and a research grant from theInternational Tree Nut Council Nutrition Research & Education Foundation.