Diet reduces insulin need in gestational diabetes

A low-glycemic index diet can significantly reduce the need for insulin in women with gestational diabetes, without compromising maternal or fetal outcomes, according to a new study.

Researchers have known that women with gestational diabetes can reduce postprandial glycemia, a spike in blood sugar that can occur just after a meal, by eating mixed meals based on low-glycemic index foods. This diet is "commonly advised as treatment for women with gestational diabetes mellitus," Dr. Robert G. Moses and co-investigators write journal Diabetes Care. "However, the efficacy of this advice and associated pregnancy outcomes have not been systematically examined."

A low-glycemic diet includes starchy foods such as potatoes, bread, and grain products, the investigators maintain. Also, the more processed a food is, the more glycemic it will be.

To further investigate, Moses, at the South Eastern Sydney and Illawarra Area Health Service in Wollongong, New South Wales, and his team studied 62 women with gestational diabetes who were about 30 weeks pregnant. Gestation diabetes is diabetes that develops during pregnancy and often disappears after delivery, but tends to signal an increased risk for diabetes and cardiovascular disease later in life. The condition may also increase complications of pregnancy.

Thirty-one women were randomly assigned to the low-glycemic index diet and 32 were assigned a high-fiber/low-sugar diet (the high-glycemic index diet). Both diets recommended a minimum carbohydrate intake of 175 grams per day, with only the choice of the type of carbohydrate foods varying.

Women on the low-glycemic index diet were counseled on the energy and nutrient balance of various foods, and were asked to avoid certain foods including white bread and processed commercial breakfast cereals. Women in the high-glycemic index diet group were just advice to avoid sugar and increase high-fiber, with "no specific mention of the glycemic index."

At an average of 32 weeks, 9 women in the low-glycemic diet (29 percent) and 19 (59 percent) in the high-glycemic diet required insulin, a statiscally significant difference.

However, instead of receiving insulin, the women on the high-glycemic index diet were switched to the low-glycemic index diet instead. The 9 patients no longer met the criteria for needing insulin. Both groups on the modified diet achieved a similar glycemic index value by the final visit at 35 to 37 weeks of gestation.

"Overall," the authors report, "there were no significant differences in obstetric and fetal outcomes between the two groups."

SOURCE: Diabetes Care, June 2009.