With its stunning landscapes and pristine blue shores, the small Japanese island of Okinawa boasts an unusually high number of centenarians. Longevity researcher Dan Buettner has long been fascinated by the secrets behind the remarkable longevity of Okinawa's residents.

During his research, he met 104-year-old Ushi Okushima, who attributed her long life to a diet rich in vegetables and mugwort sake. One staple in Ushi's diet, and that of many Okinawans, is the 'world's healthiest vegetable' - the Beni Imo, or purple sweet potato.

According to Dan, this superfood has been a reliable source of nutrition for Okinawans, even during times of famine.

He wrote: "The one food they could count on was the Beni Imo, or Okinawan sweet potato, a purple variety related to the orange sweet potato that Americans know. Sometimes they ate imo for breakfast, lunch and dinner."

Dan highlighted the five key nutrients that make Beni Imo a powerhouse of nutrition: "Fortunately for the islanders it also happened to be one of the healthiest foods on the planet, with vitamin C, fibre, carotenoids, flavonoids, and slow-burning carbohydrates."

Boasting more than just vitamin C and fibre, the Beni Imo, a Japanese culinary treasure, is also loaded with beneficial carotenoids and flavonoids, which significantly contribute to its health-boosting properties.

Carotenoids

In explaining the importance of carotenoids, dietitian Devon Peart from Cleveland Clinic remarked: "Antioxidants protect your cells from the damage that oxidation causes," and further mentioned that they can be key in reducing disease risk, such as cancer and heart disorder.

She elaborated on the heart benefits by saying: "In addition to their antioxidant effect, carotenoids are anti-inflammatory, which helps protect the heart and prevent blockages in the walls of the arteries."

Flavonoids

A study called Important Flavonoids and Their Role as a Therapeutic Agent, carried out by a group of experts, has revealed the various health benefits associated with consuming flavonoid-rich foods.

The researchers concluded: "Thus, including different types of flavonoids in daily diet is highly recommended to stay healthy and to reduce the risk of serval life threatening diseases such as diabetes mellitus, cancer as well as lowering the risk of having stroke and heart attack.

"The therapeutic effects of flavonoids have been proved in majority of pre-clinical studies in murine models."

In addition to Beni Imo, other nutritious foods such as berries, onions, and soybeans are also rich in flavonoids.