LOS BANOS, PHILIPPINES — The glycemic index (G.I.) of rice tends to vary substantially between varieties, although most types have a low to medium G.I., according to a research team from the International Rice Research Institute (I.R.R.I.) and Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) Food Futures Flagship.

The study of 235 types of rice from around the world found the G.I. of rice ranges from a low of 48 to a high of 92, with an average of 64. Low G.I. foods are those measured 55 and less, while medium G.I. foods measure from 56 to 69 and high G.I. foods measure from 70 and above.

The researchers also identified the key gene that determines the G.I. of rice, an achievement they said offers rice breeders the opportunity to develop varieties with different G.I. levels to meet consumer needs.
Melissa Fitzgerald, who led the I.R.R.I. team, defined G.I. as a measure of the relative ability of carbohydrates in foods to raise blood sugar levels after eating.

“Understanding that different types of rice have different G.I. values allows rice consumers to make informed choices about the sort of rice they want to eat,” she said. “Rice varieties such as India’s most widely grown rice variety, Swarna, have a low G.I. and varieties such as Doongara from Australia and Basmati have a medium G.I.”

Tony Bird, a researcher with CSIRO Food Futures Flagship, added that low-G.I. diets offer a range of health benefits.

“Low-G.I. diets can reduce the likelihood of developing type 2 diabetes, and are also useful for helping diabetics better manage their condition,” Dr. Bird said. “This is good news for diabetics and people at risk of diabetes who are trying to control their condition through diet, as it means they can select the right rice to help maintain a healthy, low-G.I. diet.”

The researchers noted eating rice with other foods may help reduce the overall G.I. of a meal and, when combined with regular exercise, may reduce the chances of getting diabetes. In addition, people who exercise need more carbohydrates in their diet and may be able to take advantage of low-G.I. foods for sustained activity.