Definitions of a Low Medium or High GI Food or Diet

In general, if the GI number of a food is higher than 70, the food is considered to have a 'high' GI value. If the number is lower than 55, it has a 'low' GI. Medium GI foods have GIs in the range of 55-70. But because the methods used to calculate GI are not always standard (e.g. glucose and bread are both used for comparison), knowing the exact GI number may not be as important as knowing if a food is a 'low', 'moderate', or 'high' GI food.

In general, low GI foods include non-starchy vegetables, fruits, dairy products, lentils and sugars such as fructose and lactose. Moderate GI foods are unprocessed grains and mixed dishes. High GI foods are refined grains and potatoes. Table 1 lists examples of low, moderate, and high GI foods.

The GI of foods can be modified by changing the nature of starch (e.g. increasing amylopectin or decreasing amylose or by combing starch with protein [gluten]); altering cooking methods (e.g. reducing the extent of gela-tinization or cooling to prevent retrogradation); using larger particle or piece size, adding some acids such as those in vinegar and lemon juice; adding soluble fibers such as psyllium, or by adding or substituting lactose, fructose, or sucrose for starch or glucose.

It is likely that most people already eat a moderate GI diet. In the Nurses Health Study, the lowest quintile of GI for women was 64 and in the highest quintile 77, a difference of only 13 units [4]. In the Health Professional

Table 1. Examples of low, moderate, and high glycemic index (GI) foods

Low GI foods

Moderate GI foods

High GI foods

Whole grain breads

Rye bread

White bread

Bran cereals

Frosted flakes

Corn flakes


Soft drinks


Non-starchy vegetables

Ice cream

Instant mashed potatoes



Sports drinks

Ice cream premium


Baked potatoes

Reduced fat yogurt



Oatmeal (slow cook oats)



Lentils/baked beans

Candy bars


Study, GI was 65 in the lowest quintile for men and 79 in the highest, again a difference of only 14 units [5]. In the Insulin Resistance and Atherosclerosis Study, the average caloric intake was reported to be 1,987 kcal/day with 220 g/day of digestible carbohydrate, 19 g/day of fiber, and an average GI of 58 and an average GL of 128 [6]. It is unknown if further lowering of the GI can be achieved long-term. Such small differences suggest that it may be both impractical and unreasonable to drive the GI down in the general population. In the only 1-year study published thus far, one group of individuals attempted to follow a low GI diet while the other group ate their usual foods [7]. At the end of the year there was no significant difference in the GI between groups.

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