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Understanding the Glycemic Index is Critical for Medical Weight Loss and Overall Health Nutrition In-Depth Glycemic Index
A comprehensive list of the glycemic index of foods was published in July 2002, in an issue of American Journal of Clinical Nutrition. It included almost 750 foods, which included angel food cake to yams. The University of Sydney in Australia maintains an updated database at www.glycemicindex.com that has almost 1600 entries. Maintaining a diet rich in high-glycemic –index foods, which cause sharp and strong increases in blood sugar levels, is linked with an increased risk for diabetes, heart disease, and being overweight or obese. Research being conducted links high-glycemic diets to age related macular degeneration, ovulatory infertility, and colorectal cancer. Foods with a low glycemic index have been shown to help control type 2 diabetes and improve weight loss. Other studies have found that the glycemic index has little effect on weight loss or health. This sort of disagreement is normal in the process of science, and it means that the true value of the glycemic index is yet to be determined. In the meantime, eating whole grains, beans, fruits, and vegetables—all foods with a low glycemic index—is undeniably good for many aspects of health. One of the most important factors that determine a food’s glycemic index is how much it has been processed. Milling and grinding is the process of removing the fiber-rich outer bran and the vitamin and mineral rich inner germ, leaving the starchy endosperm. (See Nutrition In-Depth for more information on what affects a food’s glycemic index). A food’s glycemic index does not tell us how much digestible carbohydrate it delivers. As an example, let us look at watermelon. This sweet fruit has a very high glycemic index, but a slice of watermelon has only a small amount of carbohydrate per serving. That is why researchers developed a way to classify foods that takes into account the amount of carbohydrates and the impact of that carbohydrate on blood sugar levels. This way of measuring is called the glycemic load. The glycemic load of a food is calculated by multiplying the glycemic index by the amount of carbohydrate it contains. Generally, a glycemic load of 20 or more is high, 11 to 19 is medium, and 10 or lower is low. You should not use the glycemic index to choose your nutritional intake. As an example a Snickers bar has a glycemic index of 41, which is considered a low glycemic index food. Although it is marked as a low glycemic index food, it is far from a health food. Instead, use it as a general guide. When you can, replace highly processed grains, cereals, and sugars with minimally processed whole grain products. Good Carbs, Not No Carbs There are popular diets out there that make carbohydrates evil, the root of all body fat and excessive weight. The Atkins diet certainly popularized the no-carb approach to dieting. In addition, there is some evidence that a low-carbohydrate diet can help people lose weight quicker than a low-fat diet, but so far, that evidence is short-term. In two short, head-to head assessments, low-carb approaches worked better than low-fat diets. A subsequent year-long study that was published in 2007 in the Journal of the American Medical Association, showed the same thing. In this study, overweight, premenopausal females went on 1 of 4 diets: Atkins, Zone, Ornish, or LEARN, a standard low-fat, moderately high –carb diet. All of the women steadily lost weight for 6 months; the most rapid weight loss was amongst the Atkins dieters. After that, most of the women regained weight. The study concluded after a year; the women in the Atkins group had lost the most weight, about 10 pounds, compared with 6 pounds in the LEARN group, 5 in the Ornish group, and 3.5 in the Zone group. Levels of bad LDL, and other blood fats were as good among females on the Atkins diet as those on the low-fat diet. If you read the fine print of the study, you would see that most of the women did not stick to their assigned diets. Those on the Atkins were supposed to limit their carbohydrate intake to 50 grams a day, but they ingested almost triple that amount. The Ornish dieters were supposed to limit their fat intake to under 10% of their daily calories, but they got about 30% from fat. There were similar variations for the Zone and LEARN group. What this and other diet studies tell us is that sticking with a diet is more important than the diet itself. No one knows the long-term effects of eating little or no carbohydrates. Another factor that causes speculation is eating unhealthy fats in some of these diets. If you decide to go on a low-carb route, try to include some fruits, vegetables, and whole grain carbohydrates every day. These foods have vitamins, minerals, and phytonutrients that are necessary for good health. Do your heart a favor and choose healthy fats and proteins to accompany the healthy carbohydrates. A 20-year long prospective study of 82,802 women looked at the correlation between lower carbohydrate diets and heart disease. Another study looked at lower carbohydrate diets and the risk of diabetes. In the long run, women who ate low-carbohydrate diets high in vegetable sources of fat or protein had a 30% lower risk of heart disease, a lower risk of type 2 diabetes in comparison to women who ate high-carbohydrate, low-fat diets. On the other hand, women who ate low-carbohydrate diets that were high in animal fats or proteins did not have a reduced risk of heart disease or diabetes. Adding Good Carbohydrates For excellent health, eat grains from intact foods like whole wheat bread, brown rice, whole grain pasta, and other unfamiliar grains like quinoa, whole oat and bulgur. These foods will help protect you against a range of chronic diseases and will please your palate. Once a rarity at mainstream grocery stores, whole-grain products are now available at most grocery stores, as well as organic stores. The following are some suggestions for adding more good carbohydrates to your diet:
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