HealthDay News — Cardiovascular risk factors such as insulin sensitivity, lipid levels, and systolic blood pressure may not be improved with a low-glycemic index (GI) diet, research published in the Journal of the American Medical Association indicate.

“Foods that have similar carbohydrate content can differ in the amount they raise blood glucose,” wrote Frank Sacks, MD, of the Harvard School of Public Health in Boston, and colleagues.

“The effects of this property, called the glycemic index, on risk factors for cardiovascular disease and diabetes are not well understood.”

To determine the effect of glycemic index and amount of total dietary carbohydrate on risk factors for cardiovascular disease and diabetes, the researchers conducted a randomized crossover-controlled feeding trial involving 163 overweight adults.

Four diets were assigned. All of the regimens were based on the Dietary Approaches to Stop Hypertension (DASH) diet but differed in the carbohydrate content, and either high or low in GI.

After five weeks on one diet, the study volunteers switched to a different one. All of the participants ate their main meal of the day at the research center. They were then given their other meals and snacks to take home.

On average, all four diets shaved four to nine points from the participants’ blood pressure, the researchers found. But when it came to improving insulin sensitivity, it was the high-carb/high-GI diet that got the best results.

In contrast, people’s insulin sensitivity barely changed when they followed the high-carb/low-GI diet. Similarly, people saw bigger improvements in low-density lipoprotein cholesterol on a high-GI diet — no matter what the carb content — compared with the high-carb/low-GI diet.

“In the context of an overall DASH-type diet, using glycemic index to select specific foods may not improve cardiovascular risk factors or insulin resistance,” concluded the study authors.


  1. Sacks FM et al. JAMA. 2014; doi: 10.1001/jama.2014.16658