Wolever T M
Department of Nutritional Sciences, St. Michael's Hospital, Faculty of Medicine, University of Toronto, Ontario, Canada.
World Rev Nutr Diet. 1990;62:120-85.
Different starchy foods produce different glycemic responses when fed individually, and there is evidence that this also applies in the context of the mixed meal. Methods of processing, and other factors unrelated to the nutrient composition of foods may also have major effects on the glycemic response. The reason for differences in glycemic response appears to relate to the rate at which the foods are digested and the many factors influencing this. The glycemic index (GI) is a system of classification in which the glycemic responses of foods are indexed against a standard (white bread). This allows the results of different investigators to be pooled. GI values also depend upon a number of nonfood-related variables. The method of calculation of the glycemic response area is most important, but the method of blood sampling and length of time of studies also may have effects. Variability of glycemic responses arises from day-to-day variation in the same subject and variation between different subjects. There is less variability between the GI values of different subjects than there is within the same subject from day to day. Therefore, the mean GI values of foods are independent of the glucose tolerance status of the subjects being tested. Potentially clinically useful starchy foods producing relatively flat glycemic responses have been identified, including legumes, pasta, barley, bulgur, parboiled rice and whole grain breads such as pumpernickel. Specific incorporation of these foods into diets have been associated with reduced blood glucose, insulin, and lipid levels. Low-GI foods may influence amino acid metabolism although the implications of these are unknown. In addition, low GI foods increase colonic fermentation. The physiologic and metabolic implications of this relate to increased bacterial urea utilization, and to the production and absorption of short chain fatty acids in the colon. The application of the GI to therapeutic diets should be in the context of the overall nutrient composition of the diet. High-fat or high-sugar foods may have a low GI, but it may not be prudent to recommend these foods solely on the basis of the GI. It is therefore suggested that the most appropriate use of the GI is to rank the glycemic effects of starchy foods which would already have been chosen for possible inclusion in the diet on the basis of their nutritional attributes, i.e. low-fat, unrefined carbohydrate.
不同的淀粉类食物单独食用时会产生不同的血糖反应，并且有证据表明在混合餐的情况下也是如此。加工方法以及与食物营养成分无关的其他因素也可能对血糖反应产生重大影响。血糖反应存在差异的原因似乎与食物的消化速度以及影响这一速度的诸多因素有关。血糖生成指数（GI）是一种分类系统，其中食物的血糖反应以一种标准（白面包）为参照进行索引。这使得不同研究者的结果能够汇总。GI值还取决于一些与食物无关的变量。血糖反应面积的计算方法最为重要，但采血方法和研究时长也可能有影响。血糖反应的变异性源于同一受试者的日常变化以及不同受试者之间的差异。不同受试者的GI值之间的变异性小于同一受试者每日之间的变异性。因此，食物的平均GI值与被测试受试者的葡萄糖耐量状态无关。已确定一些产生相对平稳血糖反应的、具有潜在临床用途的淀粉类食物，包括豆类、意大利面、大麦、碎粒小麦、半熟米以及诸如裸麦粗面包之类的全谷物面包。将这些食物具体纳入饮食与血糖、胰岛素和血脂水平降低有关。低GI食物可能会影响氨基酸代谢，尽管其影响尚不清楚。此外，低GI食物会增加结肠发酵。这在生理和代谢方面的影响涉及细菌对尿素利用的增加，以及结肠中短链脂肪酸的产生和吸收。GI在治疗性饮食中的应用应结合饮食的整体营养成分。高脂肪或高糖食物可能具有低GI，但仅基于GI推荐这些食物可能并不明智。因此，建议对GI最恰当的使用是对基于其营养特性（即低脂、未精制碳水化合物）已被选作可能纳入饮食的淀粉类食物的血糖影响进行排序。
