Large study links nut consumption to reduced death rate
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.
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, Brazil nuts, cashews, macadamias, pecans, cashews, pistachios and pine nuts.
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.
Health Benefits of Nut Consumption
Nuts (tree nuts and peanuts) are nutrient dense foods with complex matrices rich in unsaturated fatty and other bioactive compounds: high-quality vegetable protein, fiber, minerals, tocopherols, phytosterols, and phenolic compounds. By virtue of their unique composition, nuts are likely to beneficially impact health outcomes. Epidemiologic studies have associated nut consumption with a reduced incidence of coronary heart disease and gallstones in both genders and diabetes in women. Limited evidence also suggests beneficial effects on hypertension, cancer, and inflammation. Interventional studies consistently show that nut intake has a cholesterol-lowering effect, even in the context of healthy diets, and there is emerging evidence of beneficial effects on oxidative stress, inflammation, and vascular reactivity.
Blood pressure, visceral adiposity and the metabolic syndrome also appear to be positively influenced by nut consumption. Thus it is clear that nuts have a beneficial impact on many cardiovascular risk factors. Contrary to expectations, epidemiologic studies and clinical trials suggest that regular nut consumption is unlikely to contribute to obesity and may even help in weight loss. Safety concerns are limited to the infrequent occurrence of nut allergy in children. In conclusion, nuts are nutrient rich foods with wide-ranging cardiovascular and metabolic benefits, which can be readily incorporated into healthy diets.
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Nutrients. 2010 July; 2(7): 652–682.
Published online 2010 June 24. doi: 10.3390/nu2070652
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.
Frequent consumption of nuts may be associated with a lower risk of developing pancreatic cancer in woman, according to new findings.
The data, from a large-scale prospective study, investigated the association between nut consumption and risk of pancreatic cancer in more than 75,000 women who took part in the Nurses’ Health Study, and had no previous history of cancer.
Writing in Nature’s British Journal of Cancer, the team behind the new analysis reported that consumption of nuts - including tree nuts such as almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts - was found to be inversely associated with risk of pancreatic cancer, independent of other potential risk factors for pancreatic cancer.
“Frequent nut consumption is inversely associated with risk of pancreatic cancer in this large prospective cohort of women, independent of other potential risk factors for pancreatic cancer,” explained the research team - led by Dr Ying Bao of Brigham and Women’s Hospital and Harvard Medical School.
Bao and colleagues found that women who consumed a one-ounce serving of nuts two or more times per week had a 35% lower risk of pancreatic cancer when compared to those who largely abstained from nuts.
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.”
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The study is supported by National Institutes of Health grants UM1 CA167552, P01 CA87969, R01 HL60712, R01CA124908, P50 CA127003, and 1U54 CA155626-01, and a research grant from the International Tree Nut Council Nutrition Research & Education Foundation.
About Dana-Farber
Dana-Farber Cancer Institute is a principal teaching affiliate of the Harvard Medical School and is among the leading cancer research and care centers in the United States. It is a founding member of the Dana-Farber/Harvard Cancer Center, designated a comprehensive cancer center by the National Cancer Institute. It provides adult cancer care with Brigham and Women’s Hospital as Dana-Farber/Brigham and Women’s Cancer Center and it provides pediatric care with Boston Children’s Hospital as Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. Dana-Farber is the top ranked cancer center in New England and fifth nationally, according to U.S. News & World Report, and one of the largest recipients among independent hospitals of National Cancer Institute and National Institutes of Health grant funding. Follow Dana-Farber on Facebook and Twitter.
About Brigham and Women’s
Brigham and Women’s Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare. BWH has more than 3.5 million annual patient visits, is the largest birthing center in New England and employs nearly 15,000 people. The Brigham’s medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in patient care, quality improvement and patient safety initiatives, and its dedication to research, innovation, community engagement and educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Biomedical Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, more than 1,000 physician-investigators and renowned biomedical scientists and faculty supported by nearly $650 million in funding. For the last 25 years, BWH ranked second in research funding from the National Institutes of Health (NIH) among independent hospitals. BWH continually pushes the boundaries of medicine, including building on its legacy in transplantation by performing a partial face transplant in 2009 and the nation’s first full face transplant in 2011. BWH is also home to major landmark epidemiologic population studies, including the Nurses’ and Physicians’ Health Studies and the Women’s Health Initiative.
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Anne Doerr
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617-632-4090
Dana-Farber Cancer Institute
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Association of Nut Consumption with Total and Cause-Specific Mortality
Increased nut consumption has been associated with a reduced risk of major chronic diseases, including cardiovascular disease and type 2 diabetes mellitus. However, the association between nut consumption and mortality remains unclear.
Conclusions
In two large prospective U.S. cohorts, we found a significant, dose-dependent inverse association between nut consumption and total mortality, after adjusting for potential confounders. As compared with participants who did not eat nuts, those who consumed nuts seven or more times per week had a 20% lower death rate. Inverse associations were observed for most major causes of death, including heart disease, cancer, and respiratory diseases. Results were similar for peanuts and tree nuts, and the inverse association persisted across all subgroups.
Our results are consistent with the findings in previous, smaller studies. The Adventist Health Study showed that, as compared with nut consumption less than once per week, consumption five or more times per week was associated with reduced total mortality among whites, blacks, and elderly persons, with hazard ratios ranging from 0.56 to 0.82. Similarly, a study of a U.K. cohort, the Iowa Women’s Health Study, the Netherlands Cohort Study, and an earlier analysis of the NHS all showed significant inverse associations between nut intake and total mortality. Finally, in a recent secondary analysis within the PREDIMED (Prevencio’n con Dieta Mediterra’nea) trial, a hazard ratio for death of 0.61 (95% CI, 0.45 to 0.83) was found for consumption of more than three servings of nuts per week, as compared with no nut consumption.
Several explanations for our findings are possible. The observed associations could reflect confounding by unmeasured or poorly measured variables. However, participants in both cohorts provided detailed and repeated measures of diet and lifestyle, which allowed us to carefully control for a variety of potential confounding factors. To further minimize confounding by measured variables, we used the propensity-score method to adjust for differences between comparison groups, and the results remained largely unchanged. In addition, the inverse association persisted across subgroups defined by the potential confounding factors, further suggesting an independent association. We cannot rule out the possibility of confounding by unknown factors; however, the array-approach sensitivity analysis showed that a potential confounding effect would have to be quite large to meaningfully alter the observed associations in this study. In light of the large number of important confounding factors included in our analysis, all of which were updated regularly throughout study follow-up, it seems unlikely that such strong unmeasured confounding could fully explain the associations.
Ying Bao, M.D., Sc.D., Jiali Han, Ph.D., Frank B. Hu, M.D., Ph.D., Edward L. Giovannucci, M.D., Sc.D., Meir J. Stampfer, M.D., Dr.P.H., Walter C. Willett, M.D., Dr.P.H., and Charles S. Fuchs, M.D., M.P.H.
N Engl J Med 2013; 369:2001-2011November 21, 2013DOI: 10.1056/NEJMoa1307352