Glycemic response and health--a systematic review and meta-analysis: relations between dietary glycemic properties and health outcomes

BACKGROUND: Reduction of dietary glycemic response has been proposed as a means of reducing the risk of diabetes and coronary heart disease. The impact of glycemic response on markers of health remains to be elucidated. OBJECTIVE: We assessed the evidence relating the glycemic impact of foods to measures relevant for health maintenance and management of disease. DESIGN: This was a systematic review and synthesis of interventional evidence from literature reported on glycemic index and markers of health through the use of meta-analyses and meta-regression models. RESULTS: Data from 45 relevant publications were found to January 2005. Lower glycemic index (GI) diets reduced both fasting blood glucose and glycated proteins independently of variance in available and unavailable carbohydrate intakes. Elevated unavailable carbohydrate added to improvements in both blood glucose and glycated protein control. These effects were greater in persons with poor fasting blood glucose control. No effects were seen on fasting insulin<100 pmol/L; above this, study numbers were few but consistent with prevention of hyperinsulinemia in some but not all overweight persons. Insulin sensitivity according to a variety of measurement methods was improved by lower GI, higher unavailable carbohydrate interventions in persons with type 2 diabetes, in overweight and obese persons, and in all studies combined. Fasting triacylglycerol in addition to body weight reduction related more to glycemic load than to GI. Glycemic load reduction by >17 g glucose equivalents/d was associated with reduced body weight. CONCLUSIONS: Consumption of reduced glycemic response diets are followed by favorable changes in the health markers examined. The case for the use of such diets looks compelling. Unavailable carbohydrate intake is equally important.