Curcumin, the substance found in the spice turmeric that gives curry its color, may lower risk of type 2 diabetes, a small new study suggests.

All of the people in the study had been diagnosed with prediabetes. But according to the findings, none of the participants who took capsules of curcumin for nine months developed type 2 diabetes. By contrast, 16.4% of those who received a placebo did develop type 2 diabetes during the study period.

Type 2 diabetes is the most common type of diabetes and is closely associated with obesity. Prediabetes refers to blood sugar levels that are higher than normal, but not quite high enough to be defined as having diabetes. This condition places a person at greater risk for type 2 diabetes.

People who took curcumin also lost weight and reduced waist circumference at nine months, while their counterparts in the placebo group did not.

Exactly how the substance may reduce risk of diabetes is not fully understood. Researchers speculate that weight loss reduces insulin resistance, a condition in which the body produces the hormone insulin but does not use it properly. Insulin's job is to help the body use glucose or blood sugar for energy.

Curcumin also has potent anti-inflammatory properties. Inflammation is thought to play a role in many diseases, including diabetes.

"Prediabetes patients should be focused on diet and exercise as the first step," says researcher Somlak Chuengsamarn, MD. He is an endocrinologist at Srinakharinwirot University in Thailand. "These practices have an obvious benefit in preventing type 2 diabetes in this group."

All 240 study participants were educated on the benefits of a healthy lifestyle, including proper diet and exercise, during the three months before the study began. None were taking any medications for diabetes. Participants took either six supplement capsules a day, each of which contained 250 milligrams of curcuminoids, or a placebo. The researchers report no serious side effects from the curcumin, but a few people did develop minor symptoms, including itching and constipation.

The findings appear in Diabetes Care.

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Vivian Fonseca, MD, says the findings are "interesting and provocative, but preliminary." He is the president of medicine and science of the American Diabetes Association. He says there are tried-and-true ways to help reduce risk for type 2 diabetes. These include:

    Losing just 5% of your body weight
    Walking for 30 minutes a day, five days a week
    Eating a healthy reduced-calorie diet

"These modest lifestyle changes are more than enough to reduce risk of diabetes by 60%," he says. "It is too early to say what role curcumin may have in diabetes prevention."

John Buse, MD, agrees. He is the chief of the division of endocrinology at the University of North Carolina, Chapel Hill. "Weight loss works for sure," he says in an email. "Drugs do, too, but with more focused and therefore limited benefits, as well as the possibility of side effects."