Monday, July 16, 2012

Australia - Scientists Discover Gene That Determines Glycemic Index Of Rice

Researchers have identified the key gene that determines the glycemic index of rice, a breakthrough that offers breeders the opportunity to develop rice varieties with different GI levels.

Research analyzing 235 types of rice from around the world has identified the key gene that determines the glycemic index (GI) of rice, a breakthrough that offers rice breeders the opportunity to develop varieties with different GI levels to meet consumer needs.

The research team from the International Rice Research Institute (IRRI) and CSIRO’s Food Futures Flagship narrowed down the candidates to one – Waxy was found to be the main gene associated with GI in this study.

They then carried out the first large-scale phenotyping of this Waxy trait and discovered a large variability in GI in the rice varieties, ranging from a low of 48 to a high of 92, with an average of 64.

Low GI foods are those measured 55 and less, medium GI are those measured between 56 and 69, while high GI measures 70 and above.

When food is measured to have a high GI, it means it is easily digested and absorbed by the body, which often results in fluctuations in blood sugar levels that can increase chances of getting diabetes, making the management of Type 2 diabetes difficult. 

Conversely, foods with low GI are those that have slow digestion and absorption rates in the body, causing a gradual and sustained release of sugar into the blood, which has been proven beneficial to health, including reducing the chances of developing diabetes.

Dr. Melissa Fitzgerald who led the IRRI team said GI is a measure of the relative ability of carbohydrates in foods to raise blood sugar levels after eating. Rice varieties like India’s most widely grown rice variety, Swarna, have a low GI and varieties like Doongara and Basmati from Australia have a medium GI, she said.

By applying the same method used here, breeders may now be able to rapidly identify and quantify the impact of low GI rices on blood sugar status, and develop breeding programs to select for GI based on amylose content.

Future development of low GI rice would also enable food manufactures to develop new, low GI food products based on rice.

“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 GI diet,” said Dr. Tony Bird, a CSIRO Food Futures Flagship researcher.

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