The Glycemic Index, Postprandial Hypotension and Cardiovascular Disease

Abstract

High glycemic index diets have been associated with an increased risk of cardiovascular disease events and all-cause mortality. We suggest that part of the reason for this association is through the effect of the rapidly digested high glycemic index carbohydrate diets in promoting the effects of postprandial hypotension in vulnerable individuals. Postprandial hypotension has been recognized as a problem especially affecting the frail elderly. The phenomenon occurs earlier in the day and includes syncope and falls acutely and more serious cardiovascular events and increased all-cause mortality in the longer-term. The mechanism appears to relate to the rapid digestion of carbohydrates foods. Strategies that reduce the amount of meal carbohydrates and their rate of absorption by enzyme inhibition or by delaying gastric emptying and have proved helpful as has increased fluid intake, presumably due to dilution of small intestinal contents and a reduction in the tonicity, so reducing the need for intestinal fluid secretion to dilute osmotically active sugars and products of digestion. In this way the need for increased blood flow to the gut can be reduced, that would otherwise steal blood from the systemic circulation resulting in a drop in blood pressure and an increase in heart rate. Slowly absorbed or low glycemic index carbohydrates would therefore appear potentially useful as part of the dietary strategy for the treatment of postprandial hypotension and conversely postprandial hypotension could be one of the reasons why high glycemic index diets have been associated with increased CVD risk.