Eleven patients with diabetes participated in a crossover study (2 weeks on each of 2 different diets), and 13 other patients with diabetes participated in a 6-week randomized trial of the same diets. The two diets had a similar content of protein, carbohydrate, and fat, but differed by approximately five-fold in their content of advanced glycation endproducts (AGEs), which was achieved by varying the cooking time and temperature. After two weeks on the high-AGE diet, the serum concentration of AGEs increased by 64.5% (p = 0.02) and on the low-AGE diet decreased by 30% (p = 0.02); the values at six weeks were +28.2% (p = 0.06) and -40% (p = 0.02), respectively. After six weeks, the mean C-reactive protein concentration increased by 35% relative to baseline on the high-AGE diet and decreased by 20% relative to baseline on the low-AGE diet (p = 0.014).
Comment: AGEs form during the heating of common foods. They result from reactions between reducing sugars and proteins or lipids. In contrast to the AGEs that are formed in vivo, dietary AGEs form much more rapidly in the presence of heat and in far greater concentrations. The infusion of AGEs into rabbits results in the formation of atheroma-like lesions. Approximately 10% of ingested AGEs are absorbed; of that 10%, two-thirds is retained in tissues in reactive forms. The results of the present study suggest that dietary AGEs (or some other substances that are formed along with AGEs during cooking) cause an inflammatory reaction in the body, and may contribute to the pathogenesis of cardiovascular disease.
The formation of AGEs in foods can be minimized by emphasizing certain methods of cooking (e.g., boiling or poaching, as opposed to grilling or frying). In addition, heating a protein in the presence of a reducing sugar (fructose, lactose, or glucose) accelerates the formation of AGEs. Eating as many raw foods as possible is probably the best way to reduce the AGE content of the diet. For additional information on the AGE content of foods, see J Am Diet Assoc 2004;104:1287-1291.
Vlassara H, et al. Inflammatory mediators are induced by dietary glycotoxins, a major risk factor for diabetic angiopathy. Proc Natl Acad Sci 2002;99:15596-15601.
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