"Okinawa has for decades enjoyed one of the longest life-expectancy rates in the world and I think the reason for this must lie in the ingredients of the traditional diet," said Tawada, a professor of agronomy at the University of the Ryukyus in Okinawa.
Tawada has been studying getto, part of the ginger family known variously as Alpinia zerumbet, pink porcelain lily or shell ginger, for the last 20 years and now believes his work is beginning to pay off.
In a recent experiment on worms, those fed on a daily diet of getto lived an average of 22.6 percent longer than the control group.
The plant, which has large green leaves, red berries and white flowers, has been a feature of Okinawan food for centuries and still grows in the wild.
And while the people of past centuries would not have known that it is rich in resveratrol -- an anti-oxidant also found in grapes -- they knew that it was good for them, said Tawada.
"Traditionally, Okinawans have always felt that eating muchi -- a winter dish consisting of rice paste wrapped in a getto leaf -- would protect us from colds and give us strength," he said.
But things are changing in Okinawa and the traditional diet, which was rich in locally-grown vegetables, fish and seaweed, is losing ground to the steakhouses and burger chains that crowd the streets of Naha, the island chain's capital city.
Those fast food joints originally sprouted to serve the 19,000 United States servicemen who are based on the island as part of a defence treaty between Washington and Tokyo, but are now popular among the locals -- even if the soldiers, sailors and airmen are not.
Women in Okinawa still live a very long time -- 87 years on average, one of the highest rates in Japan. But men have tumbled down the rankings and, at 79.4 years, are now 30th among the country's 47 prefectures, and below the national average.
The archipelago's male obesity rate is now the highest in Japan.
"Today, people eat too much fast food," said Tawada. "Life expectancy is going down. It's time to reconnect with the culinary traditions of the region."
The health benefits of getto are beginning to spread, and a small cottage industry is growing up around Tawada's research.
Keiko Uehara, who looks considerably younger than her 64 years, swears by the stuff.
Her boutique in downtown Naha sells a whole range of beauty products with getto as the main ingredient.
"I drink an infusion of getto, which I always find rejuvenates me, and I use an extract of the plant in water to get rid of wrinkles," she said.
Out of town, Isamu Kina stands in a field full of getto. His company, Rich Green, is the main producer in the area and he has high hopes for the future.
"We don't want to be limited to Okinawa; we want to be able to export this to countries around the world," he said.
Back in his laboratory, Tawada said people are only just beginning to exploit the possibilities of the plant, which he thinks could prove transformative for the whole of Okinawa.
"Today, getto is used in cosmetics, but that's only part of its potential -- I think it can also be used in the medical field and in other sectors," he said.
"Hopefully one day it will give a facelift to the economy of the islands."