GLYCEMIC INDEX AND GLYCEMIC LOAD
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.
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 |
2½ 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 (125 g) |
6 |
Apple juice, unsweetened |
41 |
8 ½ oz (250 mL) |
12 |
Banana |
46 |
4 oz (125 g) |
12 |
Grapefruit |
25 |
4 oz (125 g) |
3 |
Grapes |
43 |
4 oz (125 g) |
7 |
Orange |
40 |
4 oz (125 g) |
4 |
Peach |
42 |
4 oz (125 g) |
5 |
Watermelon |
72 |
4 oz (125 g) |
4 |
Vegetables |
|||
Baked potato |
60 |
5 oz (150 g) |
18 |
Baked potato, mashed |
74 |
5 oz (150 g) |
15 |
Carrots |
92 |
3 oz (90 g) |
5 |
Kidney beans |
29 |
5.2 oz (150 g) |
7 |
Lentils |
29 |
5.2 oz (150 g) |
5 |
Peas |
51 |
3 oz (90 g) |
4 |
Soybeans |
15 |
5.2 oz (150 g) |
1 |
Sweet potato |
48 |
5 oz (150 g) |
16 |
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.
Both are useful—GI helps you choose better carbs while GL helps with portion sizes. Today, there are more than 750 published GI and 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, fat and protein slow down digestion, making the GL of a baked potato topped with sour cream and served with a steak different than the GL of the potato itself.
People who eat diets with a high GL have a higher rate of obesity, diabetes, heart disease, and cancer. One 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%.