Okinawan (Purple) Sweet Potato – Nutrition Facts and Health Benefits

Hawaiian purple sweet potatoes, also known as Okinawan potatoes, are packed with antioxidants, vitamins, and minerals. While presenting Okinawan sweet potato nutrition facts, this Buzzle article also describes the exceptional health benefits of this ancient diet staple.

Did You Know?

The presence of a minimum of 3-5 grams of fat in the meal enables us to absorb more beta-carotene from sweet potatoes. Adding a tablespoon of extra virgin olive oil (3.5 g fat) to mashed sweet potatoes (4 servings) can significantly improve the nutritional value of the dish.

Sweet potato is native to the tropical regions of America. However, the purple-fleshed Okinawan sweet potato is named after the Japanese island ‘Okinawa’, where it was a staple in the local diet for centuries. Currently, people of Japan have the longest average lifespan in the world, and until recently, the longest-living individuals were residents of Okinawa. Pork (rich in protein and fat), seaweed (rich in minerals), and the purple sweet potato or PSP (rich in dietary fiber, vitamins, and minerals) comprised the Okinawan diet.

There exist several varieties of the root vegetable ‘sweet potato’ (Ipomoea batatas). Some are firm, dry, and mealy, while others are soft and moist. Different varieties come with different unique tastes, however, in general, the taste is starchy and sweet. Some Ipomoea batatas are white, off-white, orange, pink, or yellow-fleshed, while the Okinawan is purple-fleshed. In Japan, it is known as beni-imo. In other parts of the world, it is referred to as Japanese purple potato or Japanese sweet potato. Sometimes, these purple sweet potatoes are called ‘purple yam,’ but yams are quite different from both sweet potatoes and common potatoes.

Although Okinawan sweet potatoes come with a brown, dull skin, they have richly colored flesh. High amounts of anthocyanin (pigments that are responsible for the red, purple, and blue colors of many fruits, vegetables, cereal grains, and flowers) present in this vegetable imparts a deep purple color to its flesh.

Sweet Potato Nutrition Facts

Okinawan Sweet Potato Calories and Nutrition

1 cup (150 g) serving of these sweet potatoes can provide 220 calories and about 1,442 retinal equivalents of vitamin A (more than 500% of the daily value). The high anthocyanin content, the deep purple color, the flavorful, dense, and creamy flesh, a richer taste, and well-balanced sweetness make them different from other sweet potato varieties.

PSP cultivars are unusually high in antioxidants. The purple anthocyanin pigments such as peonidins and cyanidins, responsible for the rich purple tones of the flesh, exhibit antioxidant and anti-inflammatory properties. The anthocyanin content may vary according to the cultivar. Studies show that the antioxidant activity in PSP cultivars is 3.2 times higher than that of a type of blueberry! All parts of Okinawan sweet potatoes exhibit antioxidant properties. Different genes in the flesh and the skin produce different concentrations of anthocyanin antioxidants. Even the leaves of the plant carry antioxidant properties and are included in soups in many cuisines. In short, purple-fleshed sweet potatoes are fat-free, low in calories, high in fiber, and are loaded with antioxidants.

Health Benefits

1. Neutralization of Free Radicals
Sporamins, storage proteins in sweet potato, also have antioxidant properties. While passing through the digestive tract, Okinawan potatoes can lower the potential health risk posed by heavy metals and oxygen radicals.

2. Antioxidant Activity
PSP extract, which has potent antioxidant activity, can be used to treat hyperlipidemic (abnormally high concentration of fats or lipids in blood) and hyperglycemic (diabetes, an excess of glucose in blood) disorders. The extract acts like an anti-atherosclerotic (hardening of arteries, due to deposition of plaque on their inner walls, is called atherosclerosis) and anti-diabetic agent.

3. Low Glycemic Index
Okinawan potatoes come with a low glycemic index. So they can be incorporated in the diet by weight watchers and diabetics. PSP can help control diabetes by improving blood sugar regulation and insulin production.

4. Prevention of Diseases
As explained above, the antioxidants in PSP help prevent cardiovascular diseases. They help control cholesterol levels. As PSP is rich in potassium, it helps regulate blood pressure. Regular consumption of steamed or boiled PSP can help prevent cancer, as the vegetable helps prevent oxidative damage to our cells. Sweet potato glycosides exhibit significant antibacterial and antifungal properties. All these characteristics help prevent infections and also reduce your risk of developing chronic diseases.

5. Anti-inflammatory Activity
The antioxidants exhibit anti-inflammatory properties too. So PSP can help lower the symptoms of arthritis and inflammation-related health problems.

6. Strong Immune System
As these sweet potatoes are packed with antioxidants, vitamins, and minerals, they help strengthen the immune system. These little purple powerhouses are a good source of vitamins A, B, and C, magnesium, potassium, calcium, and iron.

7. Hormonal Balance and Anti-aging Effect
PSP is also a good source of DHEA (dehydroepiandrosterone), a precursor hormone. As per need, DHEA gets converted into estrogen, progesterone, or testosterone. Studies show that in Western cultures, along with aging, DHEA levels drop dramatically. However, researchers have found that DHEA levels drop at a much slower rate among the long-lived Okinawans. The secret of the long life of the residents of Okinawa perhaps lies in their diet rich in purple-fleshed sweet potatoes. They not only live longer than anyone else in the world, but they also live more youthful lives even in old age.

8. Eye Health
The antioxidants, vitamins A, C, E, zinc, etc. offer some protection against the development of advanced age-related macular degeneration, especially to those who are at risk for the disease. Thus, PSP can improve visual functions.

9. Digestive Health
Fiber in PSP helps improve digestive health. It prevents indigestion, gas, constipation, stomach ache, etc. It also helps regulate blood sugar levels.

10. Improved Memory
Anthocyanins in purple sweet potatoes have memory-enhancing effects.

You can make colorful cakes, ice creams, pies, doughnuts, soups, etc., using Okinawan sweet potatoes. The striking hue can add a colorful twist to the dish. You can enjoy these potatoes baked, mashed, roasted, boiled, steamed, or sautéed. Now that you know the foods included in Okinawan diet, you can incorporate this wonderful, healthy, and naturally sweet vegetable in your meals throughout the year. Serve the sweet potatoes soon after preparation as the purple color is likely to turn grayish brown once the flesh is exposed to air.

Disclaimer: This article is for informative purposes only, and should not be replaced for the advice of a physician/nutritionist.