Randomized, Double-blind Crossover Trial Comparing Low-GI Functional vs. Standard Wholegrain Carbohydrates on Glycolipid Metabolism and Vascular Stress Markers in Adults 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.

In children and adolescents, low-GI intake improves insulin sensitivity and reduces early markers of vascular damage. A randomized controlled trial demonstrated that adolescents on a low-GI diet exhibited lower carotid intima-media thickness (IMT), a surrogate marker of atherosclerosis progression, after six months.

Furthermore, a Mediterranean dietary pattern, which is naturally low in GI due to its emphasis on legumes, whole grains, and vegetables, has been linked to a 30% reduction in major cardiovascular events in high-risk populations. The PREDIMED trial showed that such a diet significantly reduced the incidence of myocardial infarction and stroke over five years.

Inflammation plays a central role in both T2DM and CVD, and low-GI diets help reduce C-reactive protein (CRP) levels by 0.5-1.0 mg/L on average. This anti-inflammatory effect may be one of the mechanisms through which low-GI diets offer cardiovascular protection.

Even among elderly individuals, adherence to low-GI diets has been associated with better cognitive function and glycemic control. A cross-sectional analysis showed that older adults in the highest tertile of dietary GI had significantly lower memory scores than those in the lowest tertile.

The combined effects of low-GI diets-improving glucose control, reducing inflammation, enhancing lipid profiles, and promoting satiety-make them an essential component of preventive nutrition strategies for chronic disease.

Public health guidelines increasingly recommend the substitution of refined carbohydrates with low-GI alternatives to curb the global diabetes epidemic. However, no direct comparison has been made so far between functional low-glycemic index carbohydrates and standard wholegrain carbohydrates in the context of a Mediterranean diet.

In this context, the primary purpose of our research will be to evaluate if functional low-glycemic index carbohydrates are able to reduce the Triglycerides-Glucose Index plasma levels versus standard wholegrain carbohydrates in healthy subjects with suboptimal triglycerides levels. The Triglycerides-Glucose Index is a cheap, validated, emerging risk factors for both metabolic and cardiovascular diseases.