Science Daily
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 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 the New England Journal of
Medicine, contains further good news. The regular nut-eaters were found to
be more slender than those who didn't eat nuts, a finding that should alleviate
the widespread worry that eating a lot of nuts will lead to overweight.
The report also looked at
the protective effect on specific causes of death.
"The most obvious
benefit was a reduction of 29 percent 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 percent -- 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.
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.
For the new research, the
scientists were able to tap 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. A typical small packet of peanuts from a vending machine
contains one ounce.
Sophisticated data
analysis methods were used to rule out other 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, analysis was able to isolate the association
between nuts and mortality independently of these other factors.
"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 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 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 is supported by
a research grant from the International Tree Nut Council Nutrition Research
& Education Foundation and the National Institutes of Health grants UM1
CA167552, P01 CA87969, R01 HL60712, R01CA124908, P50 CA127003, and 1U54
CA155626-01.
Story Source:
The above story is based
on materials provided by Dana-Farber Cancer Institute.
Note: Materials may
be edited for content and length. For further information, please contact the
source cited above.
Journal Reference:
1.
Ying Bao, Jiali Han, Frank B. Hu, Edward L. Giovannucci, Meir J.
Stampfer, Walter C. Willett, Charles S. Fuchs. Association of Nut Consumption
with Total and Cause-Specific Mortality. New England Journal of Medicine,
2013; 369 (21): 2001 DOI: 10.1056/NEJMoa1307352