The glycaemic response

Every time we eat a carbohydrate rich meal, the carbohydrate content is broken down and digested in the gut and glucose is released into the bloodstream. This characteristic response to a carbohydrate containing meal is called the glycaemic response and is a perfectly normal physiological process. The hormone insulin is secreted in response and stimulates the removal of glucose from the circulation by muscle. In diabetics the secretion or action of insulin is defective and as a result blood glucose concentrations become elevated and can lead to long-term complications including diabetes, obesity and heart disease. Therefore diabetics research suggests that low GI diets can have favourable effects on carbohydrate and lipid metabolism and on insulin secretion. However in normal healthy subjects, the benefits of low GI diets is debatable primarily because the favourable effects of low GI diets are not known to persist for long enough to actually to have any great impact on the body.

Not all glycaemic responses are the same. Some carbohydrate containing foods produce higher peak glucose concentrations than others. In addition some carbohydrate foods produce longer glycaemic responses than others. As a result the shape of the glycaemic response curve can vary a lot from one carbohydrate containing food to another.

The concept of the glycaemic index was introduced in 1981 by Professor David Jenkins as a way of measuring the glycaemic response to a carbohydrate containing food. A low glycaemic index food is digested more slowly and as a result has a smaller impact on the peak blood glucose concentration but may produce a longer glycaemic response than a high glycaemic index food. Low glycaemic index foods are considered better for diabetics because they help minimize their exaggerated glycaemic response.