Pros and Cons of the Glycemic IndexRank Carbohydrates Using the Glycemic Index
-- By Becky Hand, Licensed & Registered Dietitian
Imagine a categorizing system in which numbers are assigned to foods, allowing you to more easily choose foods that curb appetite, help shed excess pounds, lower your risk for diabetes, help maintain blood sugar levels, and improve heart health. These are the claims of popular diets that use the Glycemic Index (GI, for short).
The Glycemic Index ranks carbohydrate-containing foods (on a scale from 0 to 100) based on their effects on blood sugar levels in the body. Foods are ranked based on how they compare to a reference food—either glucose or white bread. A food with a high glycemic index (70 or above) will elevate your blood glucose higher—and more quickly—than a food with a medium or low glycemic index (55 or less).
Highly processed and sweetened foods, such as candy or even bread made from refined white flour, tend to have a high glycemic index while less processed "whole" foods, such as an apple or whole-wheat bread tend to be lower in glycemic index. When planning meals using the glycemic index as a guide, proponents recommend choosing foods that are low or medium on the scale as often as possible. This usually is a good idea for any healthy diet because low-GI foods tend to be less processed, more nutritious and more wholesome. But plenty of good-for-you foods can have a high glycemic index (watermelon is one example), while other "unhealthy" foods like candy bars can be low on the GI scale.
Proponents of the GI diet believe that the lower the GI number of a carbohydrate food, the better. High GI foods are digested and metabolized more quickly, causing a rapid rise in blood glucose levels. This creates a dramatic spike in levels of the hormone insulin, which works to remove sugar from the blood. These responses can lead to an overproduction of insulin, contributing to weight gain. Therefore, carbohydrate foods with low glycemic indexes cause less insulin secretion and slow the clearing of glucose from the bloodstream—resulting in greater satiety, and fewer calories consumed throughout the day.
To give you an idea of how various foods rank on the glycemic index, here are a few foods along with their average GI ranking. Remember that 55 or less is considered "low," 56-69 is considered "medium" and 70-100 is considered "high" on the glycemic index. Most non-carbohydrate or low-carbohydrate foods (protein, meat, fat, nuts, oil, etc.) have a "low" glycemic index.
|Chocolate chip granola bar||78|
|Caramel rice cake||82|
(Additional information and glycemic index values can be found at www.GlycemicIndex.com and www.Mendosa.com. However, SparkPeople does not necessarily endorse the content or reliability of these websites.)
Diabetes Management: Carbohydrates and the Glycemic Index
According to the American Diabetes Association and the Academy of Nutrition and Dietetics (formerly the American Dietetic Association), there is no singular diet or meal plan that works for everyone with diabetes. People with diabetes are encouraged to work with a Certified Diabetes Educator to develop a personalized meal plan to achieve blood glucose control and weight management. Overall, research studies indicate that the total amount of carbohydrate consumed is the strongest predictor of blood glucose response, and this is typically the first tool used in the managing of blood glucose levels. For individuals needing greater blood sugar control, choosing low-glycemic carbohydrates along with a carbohydrate-controlled diet plan may produce modest results. However, it is not recommended that people with diabetes follow a low-GI eating plan alone. The amount of carbohydrates a person eats—regardless of their effects on blood sugar—is still important. <pagebreak>
Glitches in the Glycemic Index
The glycemic index is a marvelous tool for ranking carbohydrate-containing foods, but it's still in its infancy and needs additional research. It can be challenging for individuals to make healthy food choices, and the glycemic index can add another level of complication to a person's diet. Although it does have some practical benefits, here are a few of the limitations of the glycemic index.
- There is usually a wide variation in the glycemic index of any given food. Even in the chart above, the glycemic values listed are averages. One study can list a potato's glycemic index as low as 56 and another may rank it as high as 100. Therefore, the glycemic index is not an absolute—it should be thought of as a guide only.
- Many factors affect the glycemic index of a given food: ripeness, storage time, processing, preparation, and the other foods you eat with it. For example, juice has a higher glycemic index than whole fruit; mashed potatoes are higher than a baked potato, and whole-wheat bread has a higher GI than whole-wheat flour.
- Grinding and cooking can elevate the glycemic index of some foods, because these techniques make it quicker and easier for your body to digest food. For example, al dente pasta has a lower GI than soft-cooked pasta.
- Glycemic indexes are based on individual foods, but most people eat food in combinations within a meal or snack. Eating carbohydrate foods with fiber, protein, and fat will usually reduce the glycemic index of a meal as a whole.
- Every individual digests carbohydrates at a different rate, and your body's glycemic response may vary greatly throughout the day.
- Not every "high" GI food should be avoided from a nutritional standpoint. And the inverse is also true: many low GI foods aren't necessarily healthful or nutritious. When certain high glycemic foods are eliminated from the diet, so are vital vitamins, minerals, fiber, and phytochemicals. Watermelon has a "high" glycemic index of 76, but it is high in potassium, vitamin A, and lycopene, and low in calories, for example. On the other end of the spectrum, a Snickers bar has a "low" glycemic index of 43, yet doesn't contribute much in the way of nutrition. Therefore, the use of the glycemic index needs to be balanced with basic nutrition principles and healthy food choices.
- Relying on the glycemic index alone may lead to overeating and weight gain. The GI value represents the type of carbohydrate in a food (fast digesting or slow digesting), but says nothing about the amount of carbohydrates—or calories—it contains. Peanuts look like the perfect choice with a GI of 8, but with about 400 calories in 1/2 cup, they won’t help shed pounds when eaten in excess. Portion control is still relevant for managing blood glucose levels and for managing your weight.
The glycemic index is one option for ranking the healthfulness of carbohydrate-containing foods, but it's not perfect—and more research is needed. It's not a bad idea to be aware of the glycemic index and applying some of its principles when choosing carbohydrates for blood sugar control and filling power. Just don't rely fully on the glycemic index as a guide for what to eat and what to avoid. Keep the following facts in mind:
- 20% of the average American's calories come from high-carbohydrate, "empty calorie" foods, such as cakes, cookies, pies, pastries, ice cream, sugar, candy, soda pop, and chips. Current recommendations state that sugar should make up NO MORE than 7% of one’s total calorie intake.
- Fresh fruits and vegetables, and whole grains are nutritionally superior to highly processed, refined products.
- Simply limiting the total number of carbohydrates you consume at any given meal can more easily control your blood sugar levels than choosing low-glycemic foods alone can. Follow the carbohydrate range provided on your SparkPeople Nutrition Tracker, and distribute your daily total evenly among 3 meals and 1-3 snacks. By focusing on portion sizes and balanced meals throughout the day, you'll help keep your blood glucose—and hunger—levels in check.
- You probably don’t need a complicated rating system to confuse you about which carbohydrates to include in your diet. We believe that the glycemic index is just one of many tools that can help you learn about the pros and cons of various foods, but it should not be the be-all-end-all guide to healthy eating.
Nutrition Recommendations and Interventions for Diabetes: a position statement of the American Diabetes Association. American Diabetes Association, Bantle JP, Wylie-Rosett J, Albright AL, Apovian CM, Clark NG, Franz MJ, Hoogwerf BJ, Lichtenstein AH, Mayer-Davis E, Mooradian AD, Wheeler ML. Diabetes Care. 2010 Aug;33(8):1911.
The Evidence for Medical Nutrition Therapy for Type 1 and Type 2 Diabetes in Adults, Franz MJ, Powers MA, Leontos C, Holzmeister LA, Kulkarni K, Monk A, Wedel N, Gradwell E. Journal of the American Dietetic Association, 2010 Dec :110(12):1852-89.