Okinawan Cuisine: How Sweet Potatoes Came to Be a Staple Food for Centenarians

By Tim Cebula

The Japanese sweet potato, also called imo, is a cornerstone of the traditional Okinawan diet, a cuisine synonymous with good health and longevity. Yet this blue zones star ingredient became the starch of choice in this island chain not because it’s nutrient-dense or rich in antioxidants, but mostly by necessity.

The Japanese sweet potato, also called imo, is a cornerstone of the traditional Okinawan diet, a cuisine synonymous with good health and longevity. Click To Tweet

Okinawa’s subtropical islands are regularly battered by powerful seasonal storms. Rice, a Japanese cuisine staple, simply did not grow well on the island. By the 1600s, islanders turned instead to growing sweet potatoes, which they imported from China.

Okinawa’s subtropical islands are regularly battered by powerful seasonal storms. Rice, a Japanese cuisine staple, simply did not grow well on the island of Okinawa. Click To Tweet

Other practical concerns of island life in Okinawa helped strengthen the native reliance on the sweet potato. Economically, the cost of imported polished white rice was too steep for most Okinawan families. Similarly, while islanders readily ate seafood, less than 10 percent of their calories traditionally came from animal meat.

Centenarians raised on imo

The differences between traditional Japanese and Okinawan diets were often stark. About 75 percent of calories in the Japanese diet came from grains, mostly polished white rice, while only about one-third of the Okinawan diet calories were from grains, mostly millet and other grains with lower glycemic loads than rice. Japanese sweet potatoes rank low to medium on the glycemic index.

What’s more, the Japanese diet derived only about 8 percent of its calories from vegetables, which made up 58 percent of the Okinawan diet, mostly from imo. The traditional imo-packed Okinawan diet contained about 80 percent carbohydrates.

The traditional imo-packed Okinawan diet contained about 80 percent carbohydrates. Click To Tweet

As it morphed in the last several decades, the modern Okinawan diet incorporated many of the less favorable aspects of Western diets, like a marked increase in calories and eating much more meat, refined carbohydrates and sugars in processed foods, bread, and white rice. But for the centenarians in Okinawa, about 60 percent of their calories came from the sweet potato for most of their lives. Unfortunately, with the Western influence and presence of a U.S. military base, lifestyle changes have led to Okinawa being one of the least healthy prefectures in Japan. There is a 20 percent obesity rate there, whereas Japan overall has a 3-4 percent obesity rate. Okinawa is still much healthier than the U.S. where the rate is 40 percent or higher, but it is a substantial change that took place over the last few decades and Okinawa’s youth may not enjoy the longevity of their parents and grandparents.

Purple nutritional powerhouses

The flesh of the Japanese sweet potato is often purple, though sometimes orange like the sweet potatoes more common here in the United States. And like standard sweet potatoes, they’re a nutritional powerhouse.

At just 1.5 calories per gram and 220 calories per cup, the imo is a low energy density food. It’s also a good source of fiber, at 5 grams per cup. Together, this means the purple sweet potato will leave you feeling satisfied longer than you would after eating an equal amount of, say, polished white rice.

The Japanese sweet potato also delivers a whopping 500 percent of your daily vitamin A needs in just one cup. It’s also a good source of antioxidant and anti-inflammatory vitamins such as C and even E, which is a fat-soluble nutrient most often found in high-fat foods, not low-fat vegetables.

The potatoes are also a good source of B vitamins, including vitamin B6, folate, thiamin, and riboflavin. And they boast more than 700 mg of potassium per cup. The American Heart Association has said consuming high-potassium foods may help lower blood pressure by taming sodium’s harmful effects.

Taken together, the benefits of adding Japanese sweet potato – or sweet potato in general – to your diet are clear. Here are a few easy, delicious dishes to get you started: