Randomized, Double-Blind, Placebo-Controlled Crossover Clinical Trial to Evaluate the Effect of a Functional Low-Glycemic Index Carbohydrates Versus Standard Wholegrain Carbohydrates on Glycolipid Metabolism and Vascular Stress Markers in Subjects With Suboptimal Triglyceridemia

The consumption of carbohydrates with a low glycemic index (GI) has emerged as a cornerstone in the dietary prevention of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). The glycemic index classifies carbohydrate-containing foods based on their impact on postprandial blood glucose: low-GI foods have a GI ≤ 55, medium-GI between 56 and 69, and high-GI ≥ 70. Low-GI foods cause slower and smaller rises in blood glucose and insulin, which can reduce glycemic variability and postprandial hyperglycemia.

Postprandial hyperglycemia is known to trigger oxidative stress and endothelial dysfunction, mechanisms closely involved in the pathogenesis of atherosclerosis and diabetic vascular complications. Clinical trials show that replacing high-GI carbohydrates with low-GI options improves fasting blood glucose by an average of 0.4 mmol/L and HbA1c by 0.3% in individuals with impaired glucose tolerance. These modest changes translate into meaningful reductions in the long-term risk of diabetes.

A pooled analysis of 24 prospective cohort studies found that a high-GI diet was associated with a 27% greater risk of developing T2DM. Moreover, each 5-unit increment in dietary GI increases the risk of coronary heart disease (CHD) by 13%. The metabolic advantage of low-GI carbohydrates lies in their ability to limit insulin spikes, reduce inflammatory cytokine release, and lower triglyceride synthesis.

In overweight individuals, low-GI diets are associated with greater weight loss and fat mass reduction than high-GI diets, even when total calories are similar. One study found that participants on a low-GI diet lost 1.5 kg more fat mass over 12 weeks compared to those on a high-GI diet, despite identical energy intake.

Low-GI foods also improve lipid profiles. A systematic review and meta-analysis reported a mean reduction of 0.13 mmol/L in LDL cholesterol and a 0.05 mmol/L increase in HDL cholesterol among participants consuming low-GI diets. These effects are particularly relevant in patients with metabolic syndrome or insulin resistance.