More than 15 years ago, I set out to reverse-engineer a formula for longevity. Working with renowned doctors and nutritionists, I identified several Blue Zones: Places around the world where people live the longest.
Along the way, I met experts who helped me understand why the foods people ate led to longer lives. We also distilled 150 dietary surveys of centenarians, or those who live to 100 or longer, to reveal the secrets of a strong longevity regimen.
These nine simple guidelines reflect what foods (and how of much of it) Blue Zone residents eat to stay healthy:
Centenarians eat an impressive variety of garden vegetables and leafy greens (especially spinach, kale, beet and turnip tops, chard and collards) when they are in season.
During the off-season, they pickle or dry the surplus. Beans, greens, sweet potatoes, whole grains, fruits, nuts and seeds dominate Blue Zone meals all year long.
Olive oil is also a staple. Evidence shows that olive oil consumption increases good cholesterol and lowers bad cholesterol. In the Greek island Ikaria, for example, we found that for middle-aged people, about six tablespoons of olive oil daily seemed to cut the risk of premature mortality by 50%.
On average, Blue Zone residents eat about two ounces or less of meat about five times per month (usually as a celebratory food, a small side, or as a way to flavor dishes).
One 12-year study, which followed a community of 96,000 Americans in Loma Linda — a Blue Zone region in California — determined that people who lived the longest were vegans or pesco-vegetarians who ate a small amount of fish.
Vegetarians in Loma Linda, according to the researchers, were more likely to outlive their meat-eating counterparts by as many as eight years.
Okinawans in Japan probably offer the best meat substitute: Extra-firm tofu, which is high in protein and cancer-fighting phytoestrogens.
In most Blue Zones, people ate small amounts of fish, fewer than three ounces up to three times weekly.
Usually, the fish being eaten are small, relatively inexpensive varieties like sardines, anchovies and cod —species in the middle of the food chain that are not exposed to the high levels of mercury or other chemicals that pollute our gourmet fish supply today.
Again, fish is not a necessary part of a longevity diet, but if you must eat it, elect varieties that are common and not threatened by overfishing.
Beans reign supreme in Blue Zones and are the cornerstone of every longevity diet in the world: Black beans in Nicoya; lentils, garbanzo and white beans in the Mediterranean; and soybeans in Okinawa.
Most centenarians eat at least four times as many beans as Americans do on average — at least a half cup per day. And so should you. Why? Beans are packed with more nutrients per gram than any other food on Earth.
On average, they are made up of 21% protein, 77% complex carbohydrates, and only a few percent fat. Because they are fiber-rich and satisfying, they'll likely help to push less healthy foods out of your diet.
Blue Zone communities eat sugar intentionally, not by habit or accident.
They consume about the same amount of naturally occurring sugars as North Americans do, but only about a fifth as much added sugar — no more than seven teaspoons a day.
Between 1970 and 2000, the amount of added sugar in the American food supply rose by 25% (about 22 teaspoons of added sugar per day) — generally, the result of the insidious, hidden sugars mixed into soda, yogurt and sauces.
If you must eat sweets, save cookies, candy and bakery items for special occasions (ideally as part of a meal). Limit sugar added to coffee, tea or other foods to no more than four teaspoons per day.
Skip any product that lists sugar among its first five ingredients.
Eat two handfuls of nuts per day.
A handful weighs about two ounces, the average amount that Blue Zone centenarians consume: Almonds in Ikaria and Sardinia, pistachios in Nicoya, and all varieties of nuts with the Adventists in Loma Linda.
A study on food and longevity found that nut eaters outlive non-nut eaters by an average of two to three years. So try to snack on a couple handfuls of almonds, Brazil nuts, cashews, walnuts, or peanuts every day.
If you can, strive to eat only sourdough or 100% whole wheat bread.
Most commercially available breads start with bleached white flour, which metabolizes quickly into sugar and spikes insulin levels.
But bread in Blue Zones is either whole grain or sourdough. In Ikaria and Sardinia, breads are made from a variety of whole grains such as wheat, rye or barley, each of which offers a wide spectrum of nutrients.
Whole grains have higher levels of fiber than most commonly used bleached flours. Some traditional Blue Zone breads are made with naturally occurring bacteria called lactobacilli, which "digest" the starches and glutens while making the bread rise.
The process also creates an acid — the "sour" in sourdough. The result is bread with less gluten than breads labeled "gluten-free," with a longer shelf life and a pleasantly sour taste that most people like.
If possible, strive to avoid soft drinks, including diet soda. With very few exceptions, people in Blue Zones drink only coffee, tea, water and wine.
(Soft drinks, which account for about half of Americans' sugar intake, were unknown to most Blue Zone centenarians until recently.)
We found that most centenarians traditionally eat whole foods.
These are foods made from single ingredient — raw, cooked, ground or fermented — and are not highly processed. They eat raw fruits and vegetables; they grind whole grains themselves and then cook them slowly.
They also use fermentation — an ancient way to make nutrients bioavailable — in the tofu, sourdough bread, wine and pickled vegetables they eat.
And they rarely ingest artificial preservatives. Blue zones dishes typically contain a half dozen or so ingredients, simply blended together.
Dan Buettner is a longevity researcher, National Geographic Fellow and award-winning journalist. He is the author of "The Blue Zones Solution" His latest bestseller, "The Blue Zones Kitchen," fuses scientific reporting, National Geographic photography and recipes that may help you live to 100. Follow him on Instagram @DanBuettner.