Photo/IllutrationA variety of food rich in protein and vitamins (Asahi Shimbun file photo)

Japan’s varied diet has been credited by researchers as the major reason the nation ranks as world number one for healthy life expectancy, the number of years that people will enjoy without illness or disability.

A research team led by Hiroshi Shimokata, professor of geriatrics and the head of the Institute of Health and Nutrition of Nagoya University of Arts and Sciences, announced the findings on Aug. 17.

The team assessed the variety of foods in the diets of 137 nations with populations of 1 million or more, based on food supply data published by the United Nations and other sources.

According to the research, Japan had the second highest number of types of food consumed in fiscal 2010, ahead of Spain and beaten only by New Zealand. But Japan came in first for health expectancy, with people expected to remain in good health until 73.6 years old, followed by Spain at 71.9 years and Switzerland and Italy, which both stood at 71.7 years.

“When there is less variety in people’s diets, the nutrients they take in also tend to be fewer in variety,” said Shimokata. “I assume eating a wide variety of foods leads to intake of a sufficient amount of all the required nutrients, thus preventing the development of diseases.”

Healthy life expectancy for each country in this research was calculated from data on life expectancy and disability-adjusted life years for the period between 1995 and 2010.

The research team’s figures on diet showed that the wider variety of food a country has generally corresponds with more healthy years its people will enjoy.

Also, nations with a wide variety of food tend to have fewer "unfit" years in their life years that is the difference between life expectancy and health expectancy. Japanese have the third fewest unfit years.