What is the Glycemic Index?

The glycemic index (GI) ranks carbohydrates on a scale from 0 to 100 according to the extent they raise blood-sugar levels after eating.

Foods with a high GI are rapidly digested and absorbed and result in marked fluctuations in blood-sugar levels.

Low GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health.

Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger. Low GI diets also reduce insulin levels and insulin resistance.

Recent studies from Harvard School of Public Health show that the risks of diseases such as type 2 diabetes and coronary heart disease are strongly related to the GI of the overall diet. In 1999, the World Health Organisation (WHO) and Food and Agriculture Organisation (FAO) recommended that people in industrialised countries base their diets on low-GI foods to prevent the most common diseases of affluence, such as coronary heart disease, diabetes, and obesity.

When we eat carbohydrates, our blood sugar rises. The total amount of carbs we consume at a meal or in a snack mostly determines what our blood sugar will do. But the food itself also plays a role. High glycemic foods result in a quick spike in insulin and blood sugar (also known as blood glucose). Low glycemic foods have a slower, smaller effect. A serving of white rice has almost the same effect as eating pure table sugar—a quick, high spike in blood sugar. A serving of lentils has a slower, smaller effect.

Picking good sources of carbs can help you control your blood sugar and your weight. Even if you don’t have diabetes, eating healthier carbohydrate-rich foods can help ward off a host of chronic conditions, including diabetes, heart disease, and various cancers.

One way to choose foods is with the glycemic index (GI), a that tool measures how much food boosts blood sugar. The glycemic index rates the effect of a specific amount of food on blood sugar compared with the same amount of pure glucose. A food with a glycemic index of 28 boosts blood sugar only 28 percent as much as pure glucose. One with a GI of 95 acts like pure glucose.


Using the Glycemic Index:

Choose foods in the low GI class instead of those in the high GI class (see below), and limit those in between.

Most fruits and vegetables, beans, minimally processed grains, pasta, low-fat dairy foods, nuts.
White/sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.
White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, most packaged breakfast cereals.

Glycemic Index (GI) Ratings:

  • Low = GI value 55 or less
  • Medium = GI value of 56 – 69 inclusive
  • High = GI 70 or more