Low-glycemic index versus high-glycemic index Mediterranean diet: Which is better for cardiometabolic health? Original paper

In this randomized controlled study, consuming a low-glycemic-index Mediterranean diet did not improve cardiometabolic risk factors compared to a high-glycemic-index Mediterranean diet.

The effects of a low-glycemic-index (GI) versus a high-GI Mediterranean diet on cardiometabolic risk factors.

The outcomes were blood pressure, fasting glucose, total cholesterol, HDL-C, LDL-C, triglycerides, insulin, HbA1c, and HOMA-IR.

156 adults (average age of 56; 82 women and 74 men) who were considered to be at high cardiometabolic risk (i.e., they had 2 or more components of metabolic syndrome).

In this 12-week randomized controlled trial, the participants were assigned to a low-GI Mediterranean diet or a high-GI Mediterranean diet.

Both of the diets had a similar number of daily calories, carbohydrates (270 grams per day), and fiber (35 grams per day) but differed in their GI. The overall GI in the low-GI diet group was less than 55, and the overall GI in the high-GI group was greater than 70.

Half of the daily carbohydrates in the low-GI diet were from low-GI foods such as pasta, brown rice, corn tortillas, flatbread, all bran, and wheat bread plus rye and seeds. Half of the daily carbohydrates in the high-GI group came from high-GI foods like jasmine rice, potatoes, couscous, whole-grain bread, and rusks (zwieback biscuits).

In a subgroup of participants, the postprandial (postmeal) triglyceride responses to a low-GI or high-GI breakfast and lunch were evaluated for 8 hours during one day before and after the study.

In the low-GI diet group, fasting glucose, total cholesterol, and HDL-C decreased compared to baseline; however, there were no differences between the low-GI and high-GI groups for these outcomes.

The 8-hour postprandial triglyceride response was lower in the low-GI diet group than the high-GI diet group at the end of the intervention (in the subgroup of 54 participants).

The primary endpoints of this study (postprandial glucose and insulin and glycemic variability) have been previously published. Twenty-four-hour glycemic variability was reduced in the low-GI group compared to the high-GI group during the 12-week intervention.^[1]