Glycemic Index VS Glycemic Load

Like gas for a car, food is your fuel. Just as some gas is higher octane, some foods provide better fuel. To gauge how efficiently food works its way through your digestive system to affect your blood sugar, researchers at the University of Toronto developed the glycemic index (GI). The faster a food is digested and absorbed into your bloodstream, the higher its GI. High-GI foods cause a rapid increase in blood sugar, which is dangerous, especially for people with diabetes.

But GI was based on a standard measurement (50 g of carbohydrates) for all foods. In real life, people don’t tend to eat the same amounts of sugar as they do pasta or carrots.

So scientists used a little math wizardry to translate the glycemic index into more practical terms. What emerged is the glycemic load (GL). This tool considers the type of carbohydrate in the food and the amount of carbohydrate in a standard serving. By this new criterion, sugar and starchy foods and some fruits have high GL values whereas most vegetables and fruits have low GL values, meaning they are less likely to make your blood sugar spike.

Today, there are more than 750 published GL values of various foods. However, you should take all GL lists as a general guide only. As it turns out, one person’s glycemic response can differ from another’s. It may vary even in the same person from day to day. Also, the state of food can change its GL.

For example, small differences in a banana’s ripeness can double its GL. Plus, when foods are eaten together (adding butter or sour cream to a baked potato, for instance, or having the potato with a serving of meat) the GL of the combined foods becomes much different from the GL of the potato by itself. The reason is that fat and protein slow down digestion, making the GL of the whole dish different than the GL of just a single food.

USE THE GI AND GL TO SELECT FOODS
Studies have found that people who eat diets with a high GL have a higher rate of obesity, diabetes, heart disease, and cancer. One study found that men who typically ate foods with a high GL had a 40% higher chance of developing diabetes. In the Nurses’ Health Study, women who ate diets with a high GL had a 37% greater chance of getting type 2 diabetes over the 6-year span of the study. Yet another study found that swapping just one baked potato per week for a serving of brown rice could reduce a person’s odds of developing type 2 diabetes by up to 30%.

Many large health organizations, including both the Canadian and American Diabetes Associations, support the use of the GL and GI as a complement to carbohydrate counting for managing diabetes. Both are useful—GI helps you choose better carbs while GL helps with portion sizes.

GLYCEMIC INDEX VS. GLYCEMIC LOAD
Below are a few common foods and their GI and GL values. Note the differences and how the GL becomes a better way to look at the effect that foods have on blood sugar.

FOOD GI SIZE GL

Grains and Cereals
Bagel, white 72 2 ½ oz (70 g) 25
Barley, pearled 25 5 oz (150 g) 11
Bread, white 71 1 oz (30 g) 10
Bread, whole grain, pumpernickel 46 1 oz (30 g) 5
Bread, whole wheat 67 1 oz (30 g) 8
Cereal, All-Bran 50 1 oz (30 g) 9
Cereal, cornflakes 80 1 oz (30 g) 21
Cereal, muesli 66 1 oz (30 g) 16

Fruits
Apple 39 4 oz (120 g) 6
Apple juice, unsweetened 41 8 ½ oz (250 ml) 12
Banana 46 4 oz (120 g) 12
Grapefruit 25 4 oz (120 g) 3
Grapes 43 4 oz (120 g) 7
Orange 40 4 oz (120 g) 4
Peach 42 4 oz (120 g) 5
Watermelon 72 4 oz (120 g) 4

Vegetables
Baked potato 60 5 oz (150 g) 18
Baked potato, mashed 74 5 oz (150 g) 15
Carrots 92 3 oz (80 g) 5
Kidney beans 29 5.2 oz (150 g) 7
Lentils 29 5.2 oz (150 g) 5
Peas 51 3 oz (80 g) 4
Soybeans 15 5.2 oz (150 g) 1
Sweet potato 48 5 oz (150 g) 16

THE BOTTOM LINE
• Remember, GI and GL only evaluate food based on how it affects your blood sugar, and shouldn’t be used as the only ways to gauge your diet’s impact on health. Other principles of a healthy diet—variety, balance, and moderation—still apply.
• While a low-glycemic diet will include many foods recommended in a healthy diet—fruits and vegetables, whole grains, and legumes—some high-glycemic foods, such as potatoes, contain many essential nutrients and are good sources of energy, too.