Using the Glycemic Index
- The GI wasn't designed to reduce the total amount of carbohydrate people consume daily but rather to help individuals select carbohydrate foods that elicit a slower insulin response.
- Place greater focus on GI food categories rather than individual foods, selecting foods from the low and moderate categories more often than from the high category.
- Keep in mind that foods are normally eaten in combination with other foods. The amount of fat and/or protein, as well as the carbohydrate in a food, and the addition of toppings, spreads, dressings, and sauces can all influence the effect of carbohydrate on blood glucose levels.
- A simple way to moderate blood glucose response is by replacing one high-GI food with one low-GI food at each meal or snack. This is also much more realistic than totally eliminating all high-GI foods.
- It's perfectly acceptable to include high-GI foods in the diet. However, the higher the GI, the smaller the portion should be.
- Eating high-GI foods following a hard workout will help replenish glycogen stores.
- The GI is not meant to be used in isolation but rather as one component of an overall healthy eating plan that considers other nutrients (protein, fat, and fiber), portion size, and timing of meals and snacks.
While the GI is a useful tool when choosing between carbohydrates, there's another ranking system that may be more practical. The GI system ranks individual foods, which allows you to compare one to another in isolation. Yet we rarely eat only one single food at a time, and that's where the GI system has some limitations. Many factors can affect the rate at which a carbohydrate is digested and raises blood glucose levels. For instance, if you eat protein and fat along with carbohydrate, it is digested more slowly and raises blood sugar levels more gradually. Other factors that can have an impact on the GI of any food are:
- Degree of ripeness. For example, the more ripe a banana is, the higher its GI. This typically applies to all fruits that continue to ripen once harvested.
- Acids in foods. When acid is present in food, it slows the rate at which your body digests that particular food. Slower digestion means slower absorption and a more favorable effect on blood sugar.
- Individual differences in rate of carbohydrate digestion. Test five people and each will respond differently to the same food. Use the GI as a guide, but monitor the effect carbohydrate foods have on you, especially if you have diabetes.
- Type of flour (if any) in the product. The more refined white flour in a product, the higher the GI; the more whole-grain flour, the lower the GI.
- Cooking time. The cooking process makes starch molecules swell and also softens food (the longer the cooking time, the softer the food) making it easier (faster) to digest. GI numbers typically increase with cooking time.
- Other ingredients. If a high-GI food is packaged with foods containing protein or fat (such as prepared fettuccine Alfredo), the carbohydrate will have a lower GI effect than it would alone because the fat and protein slow down its digestion. By the same token, foods such as beans (legumes), which have a naturally low GI, can produce a higher GI when canned with sugar and other ingredients, as in the case of baked beans.
Watermelon's GI score can
When you calculate the glycemic load (GL), however, you get a very different picture. The glycemic load is used in conjunction with the GI. It reflects the amount of available carbohydrate in a typical serving size of a particular food, so it is more grounded in the real world of eating. The GL is calculated using a formula that multiplies the amount of available carbohydrate in a typical serving size by the food's GI and then divides the result by 100.
Let's take the watermelon example from above. We know it has a high GI. Let's see what happens when we calculate its glycemic load. A typical serving size of watermelon is 1/2 cup, the amount of available carbohydrate in it is 5.75, and its GI is 72. The GL for this food is calculated like this: 5.753724100. If you calculate correctly, you get 4.14, which is rounded to get its glycemic load rating of 4. Watermelon doesn't seem like a high-GI food anymore, does it? That's what happens when you use the carbohydrate in a reasonable serving size to determine the effect on blood sugar. Using the GL shows that it is possible to include high-GI foods in meal planning (more on this later). Remember, eliminating individual foods from your diet, especially fruits, vegetables, whole grains, and beans that may have a high GI, means you'll miss out on lots of vitamins, minerals, and fiber. You can find in-depth information on the glycemic index and search for the GI and GL of individual foods at www.glycemicindex.com.
So far, we've discussed the role carbohydrates play in weight gain. Keep reading to learn about how carbohydrates can affect other areas of your health.
Low GL = 10, Moderate GL = 11-19, and High GL = 20+
(per 50 g of available carbohydrate)