The Importance of Glycemic Index on Postprandial Glycemia and Insulinemia in the Context of the Addition of Fat to Carbohydrate Foods: A Randomized Controlled Trial on Spaghetti Versus Rice as Mixed Meals

Background:

Pasta and rice are two of the most commonly consumed grains worldwide, where the former has a low GI (e.g. spaghetti) and the latter, usually (as it depends on the type) has a higher GI (e.g. white rice). Low GI foods have been demonstrated to improve glycemic control, insulin sensitivity and diabetes management, and have been associated with reduced risk of chronic disease, including coronary heart disease. Therefore, GI is of importance as a potential dietary strategy to reduce postprandial glycemia and improve glycemic control, particularly with the increasing rates of diabetes.

Several studies have demonstrated how the addition of fat to a meal can reduce the glycemic response, some of which have suggested in a dose response manner. The mechanism by which increasing fat reduces the glycemic response may be through the effects on gastric emptying. Fat may modulate the gut hormones cholecystokinin (CCK) and peptide YY, which delay gastric emptying, which is known to be a major determinant of postprandial glycemia where small changes can have a substantial effect. Low GI foods result in lower glycemic excursions compared to higher GI foods, which, in addition to gastric emptying, may exert this effect through various pathways. Thus, there is importance of exploring the potential additional benefit beyond reducing the glycemic response with the addition of fat.

The most typical ways in which pasta and rice are consumed are with the addition of oil or tomato sauce, and are recommended to be consumed in this way in the Mediterranean diet. Among many benefits, the Mediterranean diet has been demonstrated to reduce the risk of cardiovascular disease, improved glycemic control and is encouraged in many clinical guidelines globally for both cardiovascular risk reduction and for diabetes. Some studies have explored the differences in glycemic response of different carbohydrate foods consumed with the addition of fat demonstrating that the glycemic response is indeed reduced.However, the GI may remain of importance even when other means to reduce glycemic response are introduced.

The investigators therefore designed a randomized controlled crossover study to explore whether the addition of fat in the form of commonly consumed sauces which are recommended as part of a Mediterranean diet, affects the difference in glycemic response between a commonly consumed low GI and a higher GI carbohydrate food.