The glycemic index represents a dramatic change in how carbohydrates are viewed nutritionally. Many medical experts have long regarded complex carbohydrates as healthy and simple carbohydrates as unhealthy. However, the glycemic index determines the nutritional value of carbohydrates by measuring how quickly they increase your blood-sugar levels. The index was popularized by Dr. Robert Atkins' best-selling books, which advocated restricting consumption of carbohydrates.
Explanation of Index
The glycemic index has a 1 to 100 scale. Foods with the lowest scores are considered to have the most nutritional value because they have the least impact on raising your body's blood-sugar levels. Sugar gets a 100. A food with a 50 score increases your body's blood sugar at half the rate of sugar. The glycemic index only measures carbohydrates. Atkins wrote this is justified because "fat causes virtually no blood sugar elevation and protein very little elevation."
High Glycemic Index Foods
The Harvard School of Public Health reports that foods with a score of at least 70 cause "rapid spikes" in blood sugar and are high glycemic index foods. Atkins concluded that the following carbohydrates lack nutritional value because of their high glycemic index score--corn flakes (84) and several other cereals, rice (as high as 91), bagels (72) and other breads, pineapples (66), watermelons (72), carrots (71) and baked potatoes (85). All are considered nutritious by many medical experts.
Low Glycemic Index Foods
The Harvard School of Public Health reports that foods with scores equal to or lower than 55 are digested too slowly to have a huge impact on blood sugar and are low glycemic index foods. Atkins' list of carbohydrates with a lot of nutritional value because of their low glycemic index score includes peanuts (14), cherries (22), grapefruit (25), peaches (28), pears (33) and apples (36). His recommended vegetables include cabbage, celery, eggplant, lettuce, peppers, spinach and tomatoes.
What Determines Glycemic Index?
A food's glycemic index is determined by numerous factors, reports the Harvard School of Public Health. Foods with a lot of fiber have a lower glycemic index. Foods with a lot of starch have a high glycemic index. That's why potatoes have such a high score. Ripe vegetables and fruits often have a high glycemic index because they have a lot of sugar.
The July, 2002 edition of "The American Journal of Clinical Nutrition" lists 750 foods' glycemic index. It can be read online at http://www.ajcn.org/cgi/content/full/76/1/5/T1
Medical Evidence
Atkins' books contend that you can reduce your weight and heart disease risk by not eating foods with a high glycemic index. He wrote that a 1984 to 1994 study of 75,521 nurses by Harvard University researchers Simin Liu and Walter Willett demonstrated that eating a lot of high glycemic index foods "leads to elevated blood-sugar and insulin levels, which in turn leads to hypertension, undesirable cholesterol and triglyceride levels and other risk factors for heart disease." The study's results were printed in the June, 2000 edition of "The American Journal of Clinical Nutrition."
References
- The American Journal of Clinical Nutrition: "The International Table of Glycemic Index and Glycemic Load Values"
- Harvard School of Public Health: "Carbohydrates: Good Carbs Guide the Way"
- "Dr. Atkins' New Diet Revolution;" Dr. Robert Atkins; 2002
- "Atkins Diabetes Revolution;" Dr. Robert Atkins, Mary Vernon and Jacqueline Eberstein; 2004
- "Essentials for Health and Wellness;" Gordon Edlin, Eric Golanty, Kelli McCormack Brown; 2000
