The glycemic index: an overlooked advantage

Nutrition Health Review, Spring, 2003

Just one glance at the abundance of nutrition information on food packages is enough to overload your brain, but one important statistic is not listed: the glycemic index.

Simply put, the glycemic index of food is a measure of a particular food's effect on blood glucose (sugar) levels. Carbohydrate foods that break down quickly when they are digested have the highest glycemic index values because the response to the sugars in these foods is rapid and high. Conversely, carbohydrates that break down slowly have a low number and glucose is gradually released into the bloodstream. Depending on our individual needs, we can use the glycemic index to help control certain diet-related problems, such as diabetes, coronary heart disease, and obesity.

The index is centered on a reference food (e.g., pure glucose) in equivalent carbohydrate amounts. It has been the subject of heated debates among nutritionists and scientists who could not prove that a single glycemic index food value had any relevance to the blood glucose levels of an entire meal. Recently, however, research data have proved beyond a doubt that the index has applicable value for dietary benefits, diabetes, and heart health.

Generally, many people would get the most benefit from a diet of foods having a low glycemic index value. One of the problems associated with adult-onset (type 2) diabetes is the body's resistance to insulin. Approximately 60 million Americans have insulin resistance (sometimes referred to as Syndrome X), and most do not know it until a problem arises.

Symptoms of insulin resistance include hypertension, impaired glucose tolerance, low levels of high-density lipoprotein-cholesterol (HDL-C) levels, and high triglyceride levels. The main indicator of insulin resistance is a sustained increased blood-glucose level after eating.

A diet consisting of low-glycemic-index carbohydrates, which break down slowly into the system, would ease the stress on certain tissues in the body and would promote a greater absorption and distribution of valuable insulin. This type of diet is also helpful in reducing post-meal blood glucose levels in both diabetic and nondiabetic individuals. This will allow the arterial walls to become more elastic, thereby increasing blood flow. Low-glycemic-index value foods are also ideal for preventing overnight drops in blood sugar levels as well as for long periods of exercise, such as a marathon or a gym workout that lasts more than 90 minutes.

On the other hand, healthy individuals who engage in brief periods of intense exercise might benefit from a diet of foods having a higher glycemic index value. The faster breakdown of carbohydrates into the bloodstream is also beneficial for quickly raising low blood sugar levels.

Some of the key foods that are low in glycemic index value are breakfast cereals based on wheat bran, barley, or oats, breads made with whole seeds, and whole wheat (brown) pasta and flee.

The impact of a particular food on blood glucose levels also depends on such factors as ripeness, cooking time, fiber and fat content, and recent activity. The glycemic index is just one of many tools available for diet control and optimization of insulin. As with any new diet, it is recommended that readers consult their physicians before they start.