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A new book which may revolutionize the way people with diabetes analyze food is being published out of Australia and Canada. The book, The G.I. Factor: The Glycaemic Index Solution, is a definitive look at an underutilized tool.
The glycemic index is a ranking of foods based on their immediate effects on blood glucose levels. It measures how much a person's blood glucose increases over a period of two or three hours after a meal.
The G.I. Factor is the most complete look at the glycemic index ever compiled-authored by experts in the field from around the globe. Among them are Dr. Jennie Brand Miller, head of the teaching and research staff of the Human Nutrition Unit of the Department of Biochemistry at the University of Sydney; Kaye Foster-Powell, a dietitian and nutritionist; and Dr. Stephen Colagiuri, the director of the Diabetes Centre at the Prince of Wales Hospital in Randwick, New South Wales, Australia.
Reasons For A Glycemic Index
Before the development of the glycemic index, scientists assumed that the body absorbed and digested simple sugars quickly, producing rapid increases in our blood glucose levels. This was the basis of the advice to avoid sugar, a prescription recently relaxed by the American Diabetes Association and others.
In years past, experts believed the body absorbed starches such as rice and potatoes slowly, causing only small rises in blood glucose. Clinical trials of the glycemic index have since proven that assumption to be false.
The problem is that even among the complex carbohydrates, not all are created equal. Some break down quickly during digestion and can raise blood glucose very quickly. Other carbohydrates break down more slowly, releasing glucose gradually into our bloodstreams.
The glycemic index, or what the book calls "the G.I. Factor," gives us a simple handle on the problem. It ranks on a scale of 0 to 100, indicating whether a food will raise blood glucose just a little, moderately or dramatically. The lower the number, the slower the action.
The History Of The Index
Dr. David Jenkins, a professor of nutrition at the University of Toronto, Canada, developed the concept of the glycemic index to help determine which foods had a greater impact on people with diabetes. His groundbreaking study, "Glycemic index of foods: a physiological basis for carbohydrate exchange," appeared in March 1981. In the subsequent 15 years, literally hundreds of clinical studies in the United Kingdom, France, Italy, Canada and Australia have proved the value of the glycemic index.
The United States remains "one of the last bastions of opposition," according to Dr. Brand-Miller. That's especially strange since Jenkins' original work and several subsequent studies, including some of Brand Miller's, appeared in The American Journal of Clinical Nutrition, a publication of the American Society for Clinical Nutrition.
Jenkins went on to author at least 15 more clinical studies on the glycemic index and in recent years has become one of its leading advocates. He has authored or co-authored more than 150 publications, including 50 on the glycemic index. His "International Tables of Glycemic Index," which appeared last year in The American Journal of Clinical Nutrition proceeded the publication of The G.I. Factor.
To date, hundreds of volunteers, both people with diabetes and others, have participated in the clinical trials that form the basis of knowledge of the glycemic index. The test food amount is 50 grams of carbohydrate. For example, to test boiled spaghetti, the scientists gave their subjects 200 grams of spaghetti, which according to standard food composition tables provides 50 grams of carbohydrate. The scientists compared this response with the volunteer's response to a reference food. Both for the test and for the reference foods the volunteer's response over the next two or three hours was measured. Then, they repeated the whole process on different days to reduce the effect of day-to-day variations.
How Foods Are Ranked
The G.I. Factor lists 573 separate entries, which is not 573 foods. They are instead the results of 573 studies where sets of volunteers were fed 50 grams of one food or another or mixed meals, and their glucose responses recorded. For example, three of these entries are for bulgur boiled for 20 minutes as tested by different researchers and on different subjects, some of whom have diabetes and some of whom don't.
The 573 entries show the food, its glycemic index on both the glucose and white bread standards, the number and type of subjects (whether type I, type 2, or non-diabetic), the reference food and time period (glucose or bread, 2 hours or 3 hours), and the source of the study. The sources span 80 different studies in professional journals with complete citations.
You can, of course, approximate the effect that any food has on your glucose levels. Simply, test yourself with your blood glucose meter an hour and a half or two hours after eating the food in question and compare the results with whatever standard you set for yourself. This will not be as accurate as glycemic index tests, but there is a close correlation between those tests of the total effect of a food for the two- or three-hour period after a meal and the approximate results that a home meter would report.
Eating Low G.I. Foods
With information that this book provides people are now able to choose not only different foods but also different varieties of the same food for their lower glycemic values. All sorts of beans and rice varieties which are high in amylose compared with amylopectin (different kinds of starch) have lower values than other foods. Amylose is a straight-chain molecule that is harder to digest than amylopectin, which has many branches.
Pasta has a low glycemic index. Why? Because it is prepared from semolina or cracked wheat, not wheat flour. The method of preparation is important, because the large particle size means that we absorb it more slowly.
On a personal note, I have made several changes in my diet on the basis of what I've learned about the glycemic index. One is to cook rice with half barley, because barley has such a low index, about 46.
Another is to eat a lot of chana dal, otherwise known as Bengal gram dal (cicer arietinum). This is a split yellow legume, similar to garbanzo beans (chick peas) but smaller and sweeter. Clinical trials from India and South Africa show a glycemic index of 11 and 7 respectively, just about the lowest glycemic index of any food tested. This food, generally available in Indian groceries, not only has a remarkably low index, but it also has a wonderful flavor.
I am now delighted to be able to eat fat-free ice cream and yogurt without feeling any guilt! Low-fat ice cream has an average index of 61, and artificially sweetened low-fat yogurt has an index of 14 (test results of non-fat ice cream and yogurt aren't in yet). Ice cream, despite its sugar content, has much less of an effect on blood glucose than ordinary bread. This book quite fairly points out that sugar is not just empty calories but rather a source of pleasure and reward that also helps us to limit our intake of fatty foods and high glycemic index carbohydrates.
At least a dozen studies have already looked at using the glycemic index as an aide in long-term diabetes control. All but one of these studies, the book reports, showed a clear benefit in improving blood glucose levels.
To make it even easier to apply the concept of the glycemic index the book includes 50 recipes. In addition to the standard computations of fat, carbohydrate and fiber, the recipes calculate the glycemic index of the recipe itself.
The overall importance of The G.I. Factor for people with diabetes can hardly be overstated. The only problem is its availability. The publisher hopes to sell the U.S. rights for its own edition. Meanwhile, prospective purchasers can write to:
Sydney NSW 2000
This soft-cover book is 250 pages in length and sells in Australia for $19.95 AUD. At the current rate of exchange that's $15.63 in U.S. dollars plus postage and packing, a small investment in good health.
0 comments - Aug 1, 1996
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