Plain language summary
Dietary glycaemic index (GI) is a measure of the body’s response to digesting carbohydrates. Foods with a high GI score result in a rapid spike in blood glucose and insulin levels, and increased plasma-free fatty acids. These spikes may have a direct impact on cardiovascular health. The aim of this review was to examine the effectiveness of low-GI diets in the management of blood lipids. Proposed mechanisms of high-GI diets impacting cardiovascular health include increasing reactive oxygen species, potentiating endothelial dysfunction and promoting vascular inflammation. The meta-analysis showed that low-GI diets have a significant effect on lowering total cholesterol and low-density lipoprotein (LDL) cholesterol in 5-12 weeks. Based on this study, the authors’ conclusions suggest that a low-GI diet may positively impact the lipid profile, however, a large randomised controlled trial is needed on the effects of low-GI diets on blood lipids.
BACKGROUND Dietary glycaemic index (GI) is a measure of the postprandial glycaemic response to carbohydrates. Observational studies have found increased triglycerides and decreased high-density lipoprotein levels in patients consuming higher GI foods. OBJECTIVE Our aim was to review and synthesize the evidence on the effect of low-glucose index diets on serum lipid levels. METHODS We conducted a systematic review and meta-analysis of randomized controlled trials on the effect of low-GI diets on serum lipid levels. We searched PubMed, Embase and Cochrane Library for published, English-language, randomized controlled trials comparing low-GI and high-GI diets for the management of blood lipids in the general population with at least 4 weeks of follow-up. We conducted a meta-analysis assuming a random effects model. RESULTS Four studies met the criteria for inclusion in the systematic review and meta-analysis. The individual studies did not always show a significant effect of a low-GI diet on serum lipids; however, when combined in a meta-analysis, low-GI diets were shown to have a significant effect on decreasing total cholesterol and low-density lipoprotein (LDL) cholesterol over a short time span (5-12 weeks). There was no significant effect on high-density lipoprotein or triglyceride levels. The forest plots for total cholesterol and LDL cholesterol did not show significant statistical heterogeneity (I (2) = 0%). CONCLUSION This meta-analysis suggests that a low-GI diet may help lower total and LDL cholesterol. The generalizability of these findings is likely limited by heterogeneity in individual study definitions of low- or high-GI diets.