Real World Rules From opposite sides of the globe - Toronto and Sydney - comes a real world study, demonstrating that the glycemic index (GI) provides an easy and reliable guide to help prevent type 2 diabetes. The glycemic index couldn't be simpler. It's a scale that categorizes food items according to their effect on blood sugar levels. Low GI foods (such as meat and most fruits and vegetables) prompt a slow increase in blood sugar levels, while high GI foods (such as foods with added sugar, processed baked goods and starchy foods) produce a quick spike in blood sugar levels. The problem: A steady intake of foods that generate a rapid blood sugar spike promotes a gradual insensitivity to insulin - the precursor of type 2 diabetes. But as logical as that is, the GI has its detractors. In the e-Alert "Up and Down the Ranks" (3/8/06), I told you about a study in which blood sugar levels for more than 800 subjects were tested two times, five years apart. Blood tests were accompanied by food frequency questionnaires. When researchers analyzed the dietary information to assess GI rankings and compared the results to the blood sugar tests, they found no association between high blood sugar levels and high GI levels. Based on this one trial, the lead researcher told the Associated Press that the glycemic index "should be ended altogether." That would be an absurd thing to do. Because in the real world the GI works. The June 2006 issue of the American Journal of Clinical Nutrition carries a study that measured the blood sugar response to a variety of meals in two groups of healthy subjects. STUDY ABSTRACT - At the University of Sydney, glucose and insulin responses were assessed in 16 subjects who consumed six different test meals
- At the University of Toronto, glucose response was assessed in 10 subjects who consumed eight different test meals
- The meals in each group were designed to have a wide variety of values, ranging from 220 to 450 calories, zero to 18 grams of fat, zero to 18 grams of protein, 16 to 79 grams of carbohydrates, and GI rankings from 35 to 100
- Post-meal blood tests revealed that glucose response was not related to fat or protein intake
- Carbohydrate and high GI were significantly related to glucose response
- Insulin response was very closely related to glucose response
In the conclusion to the study, the authors wrote: "GI is a significant determinant of the glycemic effect of mixed meals in normal subjects." They added that carbohydrate intake and GI together accounted for about 90 percent of the variation in the average glycemic response. Protein and fat had "negligible effects." Avoiding a blood sugar trend that leads to type 2 diabetes isn't the only GI benefit. In "Up and Down the Ranks" I also told you about a study in which subjects on a low GI diet lost more weight than those on a low fat diet. But in addition, two heart disease markers were significantly improved. Triglycerides were reduced by nearly 40 percent in low GI diet subjects, compared to low fat diet subjects whose triglycerides levels dropped by less than 20 percent. And concentrations of plasminogen activator inhibitor 1 (a coagulation factor that increases blood clot risk) increased more than 30 percent in the low-fat group, but DECREASED almost 40 percent in the low GI group. You can find more information about the glycemic index at glycemicindex.com, which has a GI database (that can be easily searched by entering the name of a food item), as well as research and individual case studies. Sources:
"Food Glycemic Index, as Give in Glycemic Index Tables, is a Significant Determinant of Glycemic Responses elicited by Composite Breakfast Meals" American Journal of Clinical Nutrition, Vol. 83, No. 6, June 2006, ajcn.org "Ex-LI Punter Sauerbrun Gets Ephedra Ban" Jason Molinet, Newsday, 7/8/06, newsday.com
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