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The glycemic index and its effects on health

The glycemic index and its effects on health

Despite its more and more frequent use as a nutritional quality criterion for improving nutrition, the index or glycemic index (GI) is still poorly understood. We take stock of this measure, which has also been the subject of controversy within the scientific community.

What is the glycemic index?

It is a method of classifying carbohydrates according to the effect they have on blood sugar (or blood sugar). Regularizing this rate is a prerequisite for preventing or controlling certain diseases, especially diabetes.

More than 20 years ago, researchers at the University of Toronto, Canada, chose about 50 carbohydrate-rich foods to study their effect on blood glucose. They adopted the glycemic index to measure a person’s blood sugar, 2 or 3 hours after eating a carbohydrate-rich food, compared to the blood glucose level of a reference food – sometimes white bread, sometimes pure glucose- providing the same amount of carbohydrates.

A food quickly digested and absorbed by the body has a high glycemic index because it quickly increases blood sugar . Conversely, a food that is slowly assimilated by the body has a low GI. Foods can have a low GI (less than 55), medium (55 to 70) or high GI (over 70). More than 750 GI values ​​for various foods have been published.

The importance of the glycemic index on health

It has long been thought that very sweet foods – fruits, pastries or chocolate – are bad for diabetics because they digest quickly and raise blood sugar levels. It was also believed that complex carbohydrates – potatoes, rice, pasta – caused more progressive glucose levels because they decompose more slowly. However, some sugars have a lower glycemic index (GI) than many starchy foods. Therefore, very sweet foods, in moderate amounts, have no more effect on blood sugar than many starchy foods and can be part of a diabetic’s menu. Research also shows that a low-GI diet may reduce the risk of getting diabetes or heart disease in healthy people.

In sports medicine, high GI foods are used as a fast energy source before and after short-term performances, and low-GI foods for endurance sports. In a completely different field, it is thought that low GI foods may help to lose weight by helping to control the level of insulin, a hormonethat, when no longer secreted by the pancreas and no longer regulates of glucose in the blood, promotes the storage of fats and prevents them from being metabolized to serve as energy.

What is the difference between glycemic index and glycemic load?

Many health organizations, including the World Health Organization (WHO), promote the use of the glycemic index in diabetics , but its usefulness is not agreed upon. The controversy comes from the practical application of this notion.

The problem is that many foods, although very good for health, have a higher GI than others that are less healthy. For example, mashed potatoes have a higher GI than sugar and, worse yet, whole wheat bread has more or less the same GI as white bread.

This is where the concept of glycemic load (CG) comes in. It is used to evaluate the effect of food on blood sugar by not taking into account only their GI. The GI indicates the speed at which a carbohydrate will turn into sugar, but not the amount of carbohydrate that goes into the composition of the food, which is also important. Watermelon carbohydrates, for example, have a very high GI, but because this fruit has very little GI, its glycemic load remains acceptable. The case of watermelon is however not frequent. When the GI is low, the glycemic load is usually low, but when it is medium or high, it can range from low to high. A glycemic load of 20 or more is considered high, between 11 and 19, average and, under 10, low

Other considerations

GI is measured by measuring blood glucose, but it differs by individual, or even day to day, for the same individual. The state of the food can also change its GI. A slight variation in the maturity of a banana , for example, raises its GI double, while that of the potato increases by 25% when it is mashed.

Food associations also play an important role. If you add butter or cream to a baked potato, or eat it with meat, you get a much lower GI than the potato alone. The explanation is simple: proteins and fats slow down the evacuation process in the stomach . It must be remembered that GI is just one of the many characteristics of a food to consider for health. Certainly, a lot of low GI foods – fruits and vegetables, whole grains and legumes- are good for your health They contain little fat, lots of fiber, vitamins, minerals and antioxidants. But some high GI foods, such as potatoes, also contain essential nutrients and are good sources of energy.

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