Okinawan Super Fruit: Key to Longevity?

Shikwasa (Citrus depressa) is a citrus fruit native to Taiwan and the Ryuku Islands (Okinawa), Japan. Shikwasa are available from August to January, and are added to numerous dishes in Japan as a flavor enhancer: added to soy sauce and used for sushi, as a salad dressing ingredient, and even put into iced teas and colas instead of lemon slices. It’s one of Japan’s summer staples, and a sharp, refreshing treat that helps to combat “natsubate” or summer exhaustion across Japan.

Known in English as the Taiwan tangerine, this small green fruit with yellow flesh like a lemon has recently been in the news for its alleged health benefits.

Shikwasa are rich in flavonoids (especially nobiletin), and have a high vitamin C content, higher than that of other citrus fruits found in Japan. In fact, it is this combination that has some researchers speculating that the nobiletin levels in shikwasa could be beneficial in terms of preventing certain cancers, combating diabetes and liver disease, and even adding in melanin/skin pigment disorders.

There is also some hope that this fruit may help to combat Alzheimer’s disease as well. The people of the Ryuku Islands are some of the longest living in the world, have relatively low levels of certain cancers, heart disease and dementia, and overall tend to  be healthier for longer. According to local belief, this all stems from their diet, which varies quite strongly from the standard Japanese diet.

As a result, the demand for shikwasa containing products across Japan has grown steadily over the years – partly as a flavor enhancer, and partly as a super food, much in the same way that chia seeds and manuka honey have boomed. You can find shikwasa soups, salad dressings, candies, jellies, and cakes with relative ease in the summer months, and wholesale purchases of this super fruit are quite high from August onward.

However, one of the most sought after products is still only available in limited quantities: shikwasa juice drinks. Juices made from 100% pure shikwasa are far too sour to drink, however in combination with other super fruits, they are highly sought after by health-conscious people of all ages. And in a market with an extremely health conscious and aging population there will be plenty of opportunities for more and more super fruit products.