An apple a day may keep the doctor away, but if you want to live longer, a handful of nuts may be a better bet, researchers reported Wednesday.
The biggest study yet into whether nuts can add years to your life shows that people who ate nuts every day were 20 percent less likely to die from heart disease, cancer or any other cause over 30 years than people who didn’t eat them.
And not only that, nuts seem to help keep the pounds off, the team at Dana-Farber Cancer Institute, Brigham and Women’s Hospital, and the Harvard School of Public Health found.
“The most obvious benefit was a reduction of 29 percent in deaths from heart disease — the major killer of people in America,” said Dr. Charles Fuchs of Dana-Farber, who led the team. “But we also saw a significant reduction — 11 percent — in the risk of dying from cancer."
Even peanuts, which technically aren’t nuts but legumes, helped. "We don’t see any difference in the benefits between peanuts and tree nuts," Fuchs said.
The study, reported in the New England Journal of Medicine, is a follow-up to many different, smaller studies that have found all sorts of benefits from eating nuts. In 2003, on the basis of those findings, the Food and Drug Administration concluded that for most nuts, eating 43 grams a day, or about 1.5 ounces, as part of a low-fat diet, may reduce the risk of heart disease, Fuchs and colleagues wrote.
Studies have found that people who eat nuts have all sorts of biological benefits: less inflammation, which is linked to heart disease and cancer; less fat packed around the internal organs; better blood sugar levels; lower blood pressure — and even fewer gallstones.
In May, researchers reported that people already eating a healthy diet who added nuts or olive oil to their diets were less likely to suffer memory loss and in February scientists reported that they cut the risk of heart attacks and strokes by 30 percent.
Both reports were based on a randomized study, in which people were assigned to eat extra nuts and olive oil. These “randomized” studies are considered more powerful, because people don’t choose which diet to adopt, so other outside factors don’t interfere with the results. For instance, people who choose to eat nuts might also dislike meat, or they might like sweets, or they might exercise more or less than people who don’t think much about eating nuts.
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But no large study has looked at whether these benefits translate to a longer life.
So Fuchs' team looked at two big studies — the 120,000-person Nurses’ Health Study, which has been watching volunteers since 1976, and the Health Professionals Follow-up Study, involving more than 50,000 men and dating back to 1986.
They’re so-called observational studies — they cannot prove cause and effect. But they also were done in real-time — people were interviewed over the years, so they’re more likely to really show what was happening.
People were asked every few years how often they had eaten a serving of nuts: never or almost never, one to three times a month, once a week, two to four times a week, five or six times a week, once a day, two or three times a day, four to six times a day, or more than six times a day.
They threw out smokers and the obese and took into account weight, other aspects of diet and salt intake.
People who ate nuts seven or more times per week had a 20 percent lower death rate, the researchers found.
“In all these analyses, the more nuts people ate, the less likely they were to die over the 30-year follow-up period,” said Dr. Ying Bao of Brigham and Women’s Hospital. Just eating nuts every once in a while lowered the death rate by 7 percent over 30 years. Eating nuts once a week lowered the death rate 11 percent, while people who ate nuts five to six times a week had a 15 percent lower death rate.
“As compared with participants who consumed nuts less frequently, those who consumed nuts more frequently were leaner, less likely to smoke, more likely to exercise, and more likely to use multivitamin supplements; they also consumed more fruits and vegetables and drank more alcohol,” Fuchs and colleagues wrote.
It's not clear what it is about the nuts that helps, says Fuchs. "We are really looking to understand what are the bioactive compounds in nuts," he says. It might be that nuts replace unhealthy snacks in the diet, but he thinks something more is going on — perhaps an effect on inflammation or metabolism.
And people who ate nuts gained less weight over time than people who didn’t.
“Eating nuts and gaining weight don't always go together. It's a matter of portion control and moderation,” said NBC News Health and Diet Editor Madelyn Fernstrom.
“As a good source of protein, heart-healthy fat, vitamins, minerals, fiber, and several antioxidants nuts are one of nature's nutrient-rich foods,” Fernstrom said. “But stick to a handful. More than that daily might pack on the pounds.”
The study was paid for by the National Institutes of Health and the International Tree Nut Council Nutrition Research & Education Foundation, but the Council had no say in how the study was done or how its results were eventually reported.
Fuchs says he's changed his eating habits because of the findings. "As a matter of fact, I went to a movie theater last month and my wife got popcorn and I got almonds," he says. "She asked me, 'Did you do that because of the study?' and I said, 'Yes.'"