White rice raises the risk of diabetes while brown rice reduces it, a study has found.
Switching from white to brown can lower the chances of developing the disease by 16%, according to experts.
Replacing white rice with all kinds of whole grain foods - which include brown rice and pasta, wholemeal bread and rolled oats - was associated with a risk reduction as great as 36%.
White rice is produced from brown rice by stripping away the outer bran and germ portions of the grain.
More than 70% of the rice consumed in developed countries such as the US and UK is white.
Like other whole grain foods, brown rice takes longer to raise blood sugar levels than "high glycaemic" refined products.
The scientists, led by Dr Qi Sun, from the Harvard School of Public Health in Boston, calculated that replacing 50g of white rice per day with the same amount of brown rice would reduce diabetes risk by 16%.
Substituting whole grains in general for white rice was associated with a risk reduction of up to 36%.
The researchers wrote in the journal Archives of Internal Medicine: "The high glycaemic index of white rice consumption is likely the consequence of disrupting the physical and botanical structure of rice grains during the refining process, in which almost all the bran and some of the germ are removed.
"The other consequence of the refining process includes loss of fibre, vitamins, magnesium and other minerals, lignans, phytoestrogens and phytic acid, many of which may be protective factors for diabetes risk."