Improving mean glycaemic index of diet by charbohydrate substitution: middle-term glicometabolic and vascular effect in humans

The main guidelines for a healthy diet suggest carbohydrates as the main source of energy. However, different carbohydrates have dramatically different bioavailability in humans and the glycaemic index is significantly associated with the risk of type 2 diabetes, coronary heart disease, and colorectal, breast, and bladder cancers in cohort studies. The most part of intervention studies have demonstrated the positive impact of the substitution of standard carbohydrates with whole grain derived foods on anthropometric and metabolic parameters of obese and/or type 2 diabetes patients. Less evidence is available on the effect of partial carbohydrate substitution in subjects with mild metabolic impairment, where a long-term whole dietary modification could be less achievable. Moreover, the most part of evidence focuses on metabolic effect without investigating the impact of dietary changes on vascular function.

We will investigate the association of quantitatively and qualitatively different carbohydrate intake pattern with a number of cardiometabolic risk factors and early vascular damage in a representative sample of overall healthy subjects from a large cohort of general population. Then, an adequately powered sample of subjects with suboptimal metabolic parameters for which a dramatic change in lifestyle nor pharmacological treatment would not be allowed will be involved in a randomized controlled cross-over clinical trial in which a standard healthy Mediterranean diet will be compared with a similar diet substituting a fixed part of the usually assumed carbohydrates with carbohydrates derived from whole grains with low glycaemic index and particularly rich in bioactive compounds beyond fibers. The short-term effect of the tested dietary modification will be evaluated in term of changes in glucose, lipid, inflammatory parameters and endothelial reactivity.

The proposed epidemiological study could help to identify subjects exposed to mildly long-term increased cardiometabolic risk based on sub-clinically impaired parameters, while the intervention study would support the background for relatively small dietary changes focused on the choice of some more healthy carbohydrates in spite of standard ones in everyday life in order to improve the individual cardiometabolic risk. In particular, the proposed dietary model could be more easily acceptable from subjects at low-risk in primary prevention for metabolic and cardiovascular diseases than whole modification of dietary habits. In fact, the proposed model could be able to mildly but significantly change a number of glucose, lipid, inflammatory parameters but probably also markers of vascular function in humans with mild metabolic impairment.