A study that compared low- and high-glycemic index diets did not find a significant difference in their effect on cardiovascular health and insulin resistance.
In the past, nutritionists have suggested foods with a low-glycemic index could improve cardiovascular function and lower the risk of developing diabetes, but a new study by the National Institutes of Health suggests otherwise.
The study found using the glycemic index to select foods most likely does not improve insulin sensitivity, lower HDL and LDL lipids levels or reduce blood pressure.
To make their findings the researchers looked at 163 overweight adults who had systolic blood pressure levels of between 120 and 159 mmHg, meaning they fell into the "high blood pressure" category. The participants spent five weeks eating one of four tested diets in which all calorie-containing food and drink items were provided by the researchers for careful control. The diets compared in the study included "high-glycemic index/high carbohydrate; low-glycemic index/ high carbohydrate; high-glycemic index/low carbohydrate; and low-glycemic index/low carbohydrate."
Each diet used the DASH eating plan with variations in carbohydrate and glycemic index levels. The DASH eating plan encourages consumption of "vegetables, fruits, and whole grains; includes fat-free or low-fat dairy products, fish, poultry, beans, nuts, and vegetable oils; and limits sweets, sugary beverages, and red meats," the NIH reported.
The team found those who ate the low-glycemic index/low-carbohydrate diet showed similar "insulin sensitivity, systolic blood pressure and HDL and LDL cholesterol levels" to those who stuck to a high-glycemic index/high-carbohydrate diet.
The American Diabetes Association still offers advice on diet and glycemic index on its website.
"The glycemic index, or GI, measures how a carbohydrate-containing food raises blood glucose. Foods are ranked based on how they compare to a reference food - either glucose or white bread. A food with a high GI raises blood glucose more than a food with a medium or low GI," the ADA stated. "Meal planning with the GI involves choosing foods that have a low or medium GI. If eating a food with a high GI, you can combine it with low GI foods to help balance the meal."
The findings were published in a recent edition of the Journal of the American Medical Association.
