High Dietary Glycemic Load Increases Risk of CVD

The glycemic load of a diet influences the risk of cardiovascular disease (CVD), particularly in people who are overweight and obese.

"Rapidly absorbed carbohydrates that induce high postprandial glucose and insulin responses have a high glycemic index," Dr. Joline W. J. Beulens and associates explain in their report, published in the Journal of the American College of Cardiology for July 3. "Glycemic load represents both quantity and quality of carbohydrates and is calculated as the product of glycemic index of a specific food and its carbohydrate content."

Dr. Beulens and her team at University Medical Center Utrecht in the Netherlands, prospectively followed more than 15,000 women ages 49 to 70, enrolled between 1993 and 1997. All were free of diabetes or CVD at baseline, when they completed food-frequency questionnaires for the previous year.

During an average of 9 years of follow-up, 556 cases of coronary heart disease and 243 cases of cerebrovascular accident were documented.

After adjusting for traditional risk factors and fat intake, the hazard ratio for CVD for the highest quartile of glycemic load compared with the lowest was 1.47 (p for trend = 0.03).

However, the association between glycemic load and CVD risk was "virtually absent in normal weight women." The increased risk of CVD manifested only among women who were overweight or obese, for whom the hazard ratio was 1.78 (p for trend = 0.04).

Further analysis showed that carbohydrate intake itself was not associated with CVD. "Therefore, our results specifically reflect the carbohydrate quality of the diet and not the carbohydrate intake itself," Dr. Beulens and colleagues indicate.
Dr. Frank B. Hu, from Harvard Medical School in Boston, explains that glycemic index ranks food based on increases in blood glucose, which is based primarily on rate of digestion and speed of carbohydrate absorption.

Foods with "more compact granules" and "high levels of viscose soluble fiber," as well as whole-grain products, have lower glycemic index values, he writes. Blood glucose response is determined not only by the glycemic index of food, but also by glycemic load, that is, the quantity of carbohydrates in food.

Dr. Hu suggests replacing refined grains and sugar with unsaturated fats and/or protein and whole grains. He also emphasizes the importance of reducing glycemic load by restricting consumption of sugar-sweetened beverages. Estimates suggest that sugary drinks currently compose 8% of total energy intake in the US diet.

Making these changes "can help prevent CVD and improve overall health, and, as such, should be considered a public health priority," he concludes.
J Am Coll Cardiol 2007;50:14-24.