Health potential of a low glycaemic index diet

What we eat affects our health, but there is considerable debate about the optimal diet. Consequently, the general public is bewildered by an avalanche of conflicting dietary information—a web search for “diet and health” generates around 460 million results. Many of these links feature the health potential of diets with a low glycaemic index (GI).

Carbohydrates are a large source of daily energy intake and the main dietary component affecting postprandial glycaemia and insulin secretion. We know that glycaemic and insulin responses are influenced by both the amount and the type of carbohydrate. In 1981, the GI was developed to rank foods according to their glycaemic effect, expressed as a percentage of the response to an equivalent carbohydrate portion of a reference food.1 The term glycaemic load was introduced in 1997 to quantify the overall glycaemic effect of a food and is calculated as the mathematical product of the food’s GI and carbohydrate content.2 Although the validity of the GI applied to individual foods is accepted, debate continues about the comparative clinical effects of high and low GI diets.

In people with …