Dietary glycemic index and glycemic load in relation with metabolic syndrome: A review on epidemiologic evidence

  Background: Nowadays, more and more attention is paid to the glycemic index (GI) of dietary carbohydrates and the glycemic load (GL) of diets.   Objective: This study was aimed to review the previous researches about the association between the dietary GI and GL and metabolic syndrome.   Methods: The present study was a literature search within PubMed. The search terms glyc(a)emic index and glyc(a)emic load were combined with metabolic syndrome and at least one of the components of metabolic syndrome, insulin resistance, insulin sensitivity, and also some of associated risk factors such as low density lipoprotein cholesterol, total cholesterol, respectively. Most studies on humans published until 2010 were considered. Reference lists within the papers reviewed were cross-checked manually . On the whole, 30 papers were studied.   Findings: The data from cross-sectional and interventional studies do not strongly support the presence of a relationship between the dietary GI or GL and insulin resistance or insulin sensitivity. Rather, the dietary fiber may be directly responsible for the reported effects of low GI diets on insulin sensitivity in humans. Considering the risk of metabolic syndrome, it is time to replace the carbohydrate resources with low GI (brown rice for white rice) to decrease the risk of metabolic syndrome and to treat the condition especially in populations with high intakes of carbohydrate. In addition, the interventional studies, unlike the cross-sectional studies, cannot strongly support the positive effects of low GI/GL diets on the components of metabolic syndrome. It seems that long-term clinical trials with large samples to obtain solid evidence are needed.   Conclusion: Taken together all mentioned studies, low GI/GL diets may benefit lipid profiles and other components of metabolic syndrome especially the individuals with higher BMI, insulin resistance or impaired glucose tolerance.