If anyone possesses the secret of a long and healthy life, it’s the people of Okinawa, in southern Japan. They really do seem to live longer than people almost anywhere else—an average of 81.2 years, compared to 78.3 in the United States, and a worldwide average of just 67.2.

Bradley Willcox, MD, co-principal investigator of the Okinawa Centenarians Study, has been working to uncover the secret of the islanders’ exceptional longevity. When we asked him by email what he’d discovered, part of his answer took us by surprise. ”Sweet potatoes,” he wrote.

It turns out that sweet potatoes are an important staple in the Okinawan diet, along with bitter melon (a tropical fruit often used in stir fries) and sanpin tea (a blend of green tea and jasmine flowers.) What do they have in common? Antioxidants, and plenty of them. One theory of aging holds that unstable oxygen molecules, called free radicals, which are normally generated by the body’s biochemical processes, keep chipping away at healthy cells, damaging and ultimately destroying them. Antixoidants neutralize these unstable molecules and protect against cellular wear and tear.

Fruits and nuts
Blueberries are especially rich in antioxidants, which may explain results from a study by researchers at the Jean Mayer Human Nutrition Research Center, who laboratory mice blueberry extract over a period of time equivalent in mouse lives to ten human years. When the blueberry mice reached old age, they outperformed a control group of mice fed regular chow on tests of balance and coordination. Antioxidants in blueberries, scientists speculate, may block oxidative damage to brain cells and blood vessels.

The antioxidant theory may help explain the remarkable longevity of another group, the Seventh Day Adventists, who typically outlive their neighbors by 4 to 7 years. Their religious denomination, founded in the U.S. in the 1840s, emphasizes healthy living and a vegetarian diet. And fruits and vegetables, of course, are the most abundant source of antioxidants in the diet. Their longevity may also be partly due to the fact that they eat little or no read meat, thus avoiding artery-clogging saturated fat, according to Joan Sabate, PhD, chairman of nutrition at Loma Linda University in California, where the Adventist studies have been conducted.

Sabate offered another more surprising explanation. Nuts. “Among Adventists, the more frequently people eat nuts, the longer they live on average. Our numbers suggest that nuts alone may account for an extra two and a half years of life.” What’s so good about nuts? First off, they are rich sources of unsaturated oils, so they offer benefits similar to those associated with olive oil. Nuts are also concentrated sources of vitamins, minerals, and other phytochemicals, including antioxidants.

Long live chocolate!
An even more surprising secret of longevity shows up in studies of the residents of the San Blas islands, off the coast of Panama. Here, people called the Kuna remain remarkably free of signs and symptoms of high blood pressure, which plagues most Americans as they get older, increasing the risk of heart disease and stroke. A study published last year showed that the Kuna’s rate of heart disease is only 9 per 100,000 people, compared to 83 per 100,000 among nearby mainland Panamanians.

The reason? Chocolate, says Harvard University professor Norman Hollenberg, MD, who has been studying the Kuna for more than two decades. The Kuna imbibe a drink made with cocoa in generous proportions—five or more glasses a day. And cocoa turns out to be unusually rich in flavonols, which help preserve the healthy function of blood vessels, especially their ability to widen or constrict as needed. Maintaining youthful blood vessels lowers risk not only of high blood pressure but other life-threatening chronic conditions, including type 2 diabetes, kidney disease, and even dementia.

Wine or other alcoholic beverages deserve a place at the table; they are consistently associated with lower mortality, as long as they’re consumed in moderation.

More important than specific foods, however, are overall eating patterns. Consider evidence from the Baltimore Longitudinal Study of Aging, which was begun in 1958 and is now the longest-running study of aging in the world, with more than 1,500 participants. A recent analysis of 501 men from the study found that those who helped themselves to lots of fruits and vegetables were less likely to develop heart disease and more likely to be alive at the end of 18 years of study. Each serving of fruits and vegetables led to a 6 percent reduction in risk of total mortality. Men who limited their saturated fat also reduced the risk of heart disease. But far and away the most impressive benefits fell to men who did both. Those who served up fruits and vegetables and cut back on saturated fat slashed their risk of dying of heart disease by 76 percent and of any cause by 31 percent during the study period.

Hara hachi bu
Because so many variables are involved, scientists can’t say exactly how many extra years of life you or I will gain by eating well and staying active. But Harvard School of Public Health epidemiologist Meir Stampfer, PhD, one of the country’s leading experts on health and nutrition, estimates that women in the Nurses Health Study who followed all the best health and diet advice might be adding an additional 14 years to their lives. Joan Sabate of Loma Linda University believes the Seventh Day Adventists add an extra ten years to their lives thanks to five lifestyle factors: being vegetarian, not smoking, exercising frequently, maintaining a healthy weight and, of course, eating lots of nuts.

According to Bradley Willcox, the Okinawans have traditionally followed hara hachi bu, a custom of eating until they are just 80 percent full. The practice allows them to consume fewer calories without bothering to read nutrition labels—and it means they don’t have to obsess about what to eat and not eat but can go about enjoying themselves.

That may be even more crucial to their longevity than, well, sweet potatoes or sanpin tea. Finding delight in family and friends, having something to look forward to every day: studies of centenarians around the world suggest that these intangibles, even more than the specifics of diet, may be the most powerful secret to longevity. The Okinawans call it ikigai, or “finding your reason to live.”

Tags: antioxidants, blueberries, chocolate, diet, ikigai, longevity, nuts, Okinawa