The new research combines two studies that started in the 1980s on 76,464 female nurses and 42,498 male health professionals. They filled out surveys on food and lifestyle habits every two to four years, including how often they ate a serving (1 ounce) of nuts.
Study participants who often ate nuts were healthier — they weighed less, exercised more and were less likely to smoke, among other things. After taking these and other things into account, researchers still saw a strong benefit from nuts.
Compared with people who never ate nuts, those who had them less than once a week reduced their risk of death 7 percent; once a week, 11 percent; two to four times a week, 13 percent; and seven or more times a week, 20 percent.
"I'm very confident" the observations reflect a true benefit, Bao said. "We did so many analyses, very sophisticated ones," to eliminate other possible explanations.
For example, they did separate analyses on smokers and non-smokers, heavy and light exercisers, and people with and without diabetes, and saw a consistent benefit from nuts.
At a heart association conference in Dallas this week, Penny Kris-Etheron, a Pennsylvania State University nutrition scientist, reviewed previous studies on this topic.
"We're seeing benefits of nut consumption on cardiovascular disease as well as body weight and diabetes," said Kris-Etherton, who has consulted for nut makers and also served on many scientific panels on dietary guidelines.
"We don't know exactly what it is" about nuts that boosts health or which ones are best, she said. "I tell people to eat mixed nuts."
