Confusion about carbohydrates is common. Carbs are important because they give your body energy. Certain kinds of carbs that we eat can quickly spike our blood sugar levels. Other carbs are slowly digested and raise the blood sugar level gradually, which helps with appetite control and cholesterol level control. Now, which kind would you rather eat? While the answer is not completely clear-cut, you can use the glycemic index as a tool to help you choose carbs carefully.
The glycemic index (GI) measures how carbohydrate-rich foods affect our blood sugar. Foods are ranked on a 0-100 scale based how much they raise blood glucose levels compared to a reference or standard food (usually white bread or glucose). That's how quickly our bodies break down carbohydrates into sugar for energy. The overall effect of a particular food's GI and the amount of carbohydrate in the food is called the glycemic load (GL).
Foods high on the GI are broken down rapidly and can quickly raise blood sugar levels. Low-GI foods are slowly digested and help control blood glucose and cholesterol levels for people with diabetes. By controlling and delaying hunger, low-GI diets have also been shown to make weight loss easier. In fact, even moderate reductions in a person's glycemic load can speed up body fat loss in overweight or obese adults.
One study compared the impact of four low-fat, high-fiber diets on an overweight or obese person's health. The difference between each diet was the quality and quantity of the carbohydrates that test subjects ate. All four diets resulted in weight loss for the overweight or obese test subjects, but the diet that featured high carbs and low-GI foods saw the best overall results, lowering LDL (bad) cholesterol and trimming body fat mass.
The Human Nutrition Unit at the University of Sydney in Australia is "home" of the glycemic index, conducting ongoing research and maintaining a database of foods and their GI rankings. Their advice is not to worry too much about the numbers game and simply focus on choosing the best foods and eating a variety of healthy foods. A few things to think about:
- Select fresh foods. In general, the more cooked and processed foods are usually higher on the GI, but this is not always the case.
- The GI rule of thumb: choose slow carbs, not low carbs. Carbs can be healthy additions to your diet (for example, they provide fiber), so you shouldn't rule out all of them. Instead, opt for carbs that are lower on the GI.
- Lots of foods, including meats, tofu, eggs, avocados, fruits, and alcoholic beverages like wine or beer, have little or no carbohydrates. Thus, they don't have a GI.
- Pasta is special. Thanks to its unique, starchy structure, the carbohydrates in pasta are less able to break down rapidly. Pasta should be cooked al dente or just a bit firm. Overcooked pasta gets a GI boost. Adding acidic ingredients like vinaigrette to a meal can reduce its GI level, and starchy high-GI potatoes can be made healthier by serving them cold, as in a refrigerated potato salad tossed with vinaigrette.
Here are some sample GI levels of some common foods:
| low GI (55 or less) |
oat bran bread, al dente pasta, chick peas, lentils, kidney beans |
| medium GI (56-69) |
new potatoes, oatmeal, popcorn, brown rice, basmati rice, whole wheat bread |
| high GI (70 or higher) |
instant mashed potatoes, baked white potato, short-grain rice, corn flakes, white bagels, soda crackers, French fries |