David J.A. Jenkins, M.D., Ph.D., D.Sc.
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"Father"of glycemic index
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Interesting slide which shows an increased risk of coronary heart disease correlating with increasing glycemic load even when corrected for BMI.
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Total antioxidant capacity is decreased more by higher GI bread than lower GI pasta.
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HDL-cholesterol goes down with increasing glycemic index.
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C-Reactive Protein, a general marker of inflammation, is increased with increasing glycemic loads.
David Mendosa - Glycemic Index
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The glycemic index ranks foods on how they affect our blood glucose levels. This index measures how much your blood glucose increases in the two or three hours after eating.
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The glycemic index is about the quality of the carbohydrates, not the quantity.
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Free Foods
Andrew Weil, M.D.
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The glycemic index ranks carbohydrate foods on the basis of how they affect blood sugar (glucose). This is important for many people because eating a lot of foods that rank high on the glycemic index will produce spikes in blood sugar that can lead over time to loss of sensitivity to insulin, the hormone needed to allow blood sugar to enter cells for use as fuel. Insulin resistance is associated with obesity, high blood pressure, elevated blood fats, and an increased risk of type 2 diabetes.
Carbs are not bad, despite the claims of the late Dr. Robert C. Atkins and other proponents of low-carb diets. Rather, there are better and worse carbs, the difference having to do with the glycemic index. I recommend using the glycemic index as a guide to healthy carbohydrate consumption. In general, avoid frequent consumption and large servings of foods that rank high on this scale. There are several GI index lists on the Internet, but one of the most complete seems to be this one: http://www.mendosa.com/gilists.htm
To create a scale for comparison, pure glucose is ranked at 100. Foods that rank over 60 are considered high glycemic index carbs. In most indexes (there is some minor variation between lists) these include potatoes, refined white and wheat bread, raisins and other dried fruit, bananas, carrots and watermelon. Foods ranked "moderate" (between 45 and 60) include most types of pasta, bulgur, baked beans, yams, green peas, sweet potatoes, orange juice and blueberries. Low glycemic index foods (below 45) include beans, cruciferous vegetables, yogurt, grapefruit, apples and tomatoes.
When using the glycemic index as a guide to food choices, you also have to consider "glycemic load," a measure of how many grams of carbohydrate a normal serving contains. For example, carrots rank high on the glycemic index, but the amount of carbohydrates you would actually consume in a normal serving is pretty low, only 6.2 grams. The low-carb folks tell people to avoid carrots (and beets), but this is not good advice. Unless you eat huge portions of them, those vegetables will not disturb your blood sugar very much, and they provide important phytonutrients.
To calculate glycemic load, multiply the number (in grams) of the carbs you would consume in a serving by the food’s ranking on the glycemic index. Although glycemic index rankings are written as whole numbers, they actually are percentages, so if the GI of a food is 71, treat this as 71% when you do the math. Foods with a low glycemic load rank from one to 10; those with medium load range from 11-19 and those with high glycemic load rank at 20 or above.
While the concept of glycemic load is helpful, doing calculations for everything you eat isn't always practical. Instead, to make better, simpler choices about carbohydrates, reduce consumption of processed and refined foods (such as snack foods, white bread, sweetened drinks, and sugary desserts). Eat more sweet potatoes and fewer white potatoes, less bread (unless it's really chewy and grainy), more whole grains and fewer products made with flour, more temperate fruits (especially berries, cherries, apples, and pears) and fewer tropical ones, and more beans.
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Divide your daily calories this way: 20-30 percent from protein; 40-50 percent from low or moderate glycemic index carbohydrates; and 30 percent fat.
Excellent Book by Dr. Jennie Brand-Miller and Dr. Thomas M.S. Wolever
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All about the glycemic index with very large lists of foods with their indexes
Factors that influence the GI value of a food
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Starch gelatinization - El dente pasta lower GI value
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Physical entrapment - grainy breads
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High amylose to amylopectin ratio - Basmati rice and legumes
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Particle size - stone ground flours
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Viscosity of fiber - rolled oats, beans, apples, metamucil
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Sugar - oatmeal cookies - restricts gelatinization of starch
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Acidity - vinegar, lemon juice - delays stomach emptying
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Fat - delays stomach emptying
Glycemic index of a meal is a sum / average of its component carbohydrates.
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High GI - 70 or higher
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Intermediate GI - 56 - 69
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Low GI - 0 - 55
The theory
High-GL foods trigger a large rise in blood sugar, followed by a
proportionate rise in insulin. Some researchers have suggested that the
unusually large rise in insulin caused by foods high in rapidly
digested carbohydrates (like table sugar or white bread) results in
weight gain for three reasons: 1) it increases enzymes that play a role
in laying down fat; 2) it reduces the body's ability to burn fat for
energy and 3) it increases appetite. The use of GI/GL dietary programs
has been endorsed by many official health agencies around the world,
most notably Australia and the World Health Organization, but they have
not been recognized by any governmental or professional entity in the
United States.
