The glycemic index is used to measure how quickly foods containing carbohydrates such as fruits, cereals, and baked goods raise glucose levels in the bloodstream.
A new study published by the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medicine, has revealed that people who follow a healthy diet rich in fruits, vegetables, whole grains and sweets do not have to worry about glycemic index as the diet naturally lowered the risk of diabetes and heart disease.
The study volunteers followed carefully planned diets high or low in carbohydrates and with high or low glycemic index scores. Tests tracked the volunteers’ blood pressure, cholesterol levels and sensitivity to insulin at the beginning and end of each diet. The results showed little difference between high and low glycemic index foods, said study co-director Lawrence J. Appel, M.D., M.P.H.
“We were really surprised,” Appel said. “We did not detect any clear benefit of the low glycemic index diets on the major risk factors for heart disease, and we found no evidence of benefit for diabetes prevention.”
The research authors looked closely at other studies focusing on the use of low glycemic index foods in weight control. “The evidence has been inconsistent that low glycemic foods help people lose more weight or keep it off,” Appel said. “In looking at the causes of obesity and ways to combat it, a narrow focus on the glycemic index seems to be unwarranted.”
One hundred sixty three volunteers from Baltimore and Boston participated in the study. All were overweight and had above normal blood pressure, and were randomly assigned to follow one of four diets.
Researchers tested the volunteers’ blood pressure; sensitivity to insulin; and levels of “good” high-density lipoprotein (HDL) cholesterol, “bad” low-density lipoprotein (LDL) cholesterol and triglycerides, fat molecules, or lipids, that play a role in heart health. The low glycemic index diets did not lower blood pressure or LDL cholesterol, and they did not improve insulin resistance.
The researchers recommend following a basic healthy diet. “Get back to the basics that most people already know,” said study co-director Lawrence J. Appel, M.D., M.P.H., a professor of medicine and director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medicine. “Don’t drink sugar-sweetened drinks. Try to eat fruits, vegetables and whole grains. Try to avoid sweets, salt, and foods high in saturated and trans fats. People who follow these principles will reap the benefits.”
Frank M. Sacks, Vincent J. Carey, Cheryl A. M. Anderson, Edgar R. Miller, Trisha Copeland, Jeanne Charleston, Benjamin J. Harshfield, Nancy Laranjo, Phyllis McCarron, Janis Swain, Karen White, Karen Yee, Lawrence J. Appel. Effects of High vs Low Glycemic Index of Dietary Carbohydrate on Cardiovascular Disease Risk Factors and Insulin Sensitivity. JAMA, 2014; 312 (23): 2531 DOI: 10.1001/jama.2014.16658