Carbohydrate as a nutrient in adults: range of acceptable intakes.

This review considers the acute and chronic effects of different levels of carbohydrate (CHO) intakes. The type of CHO consumed, especially glucose vs fructose, affects the glycaemic, insulinaemic and thermogenic responses. In addition, other aspects of food (type of starch, method of processing or cooking, presence of other nutrients) affects the glycaemic response (glycaemic index). In general, the greatest benefit to health is derived from consuming foods with a low glycaemic index and a high non-starch polysaccharide (fibre) content. Healthy, moderately active adults require at least 200g CHO per day to sustain normal brain metabolism and muscle function. Moreover, the CHO content should represent at least 50% of energy intake. Higher intakes of CHO can have deleterious effects on blood lipids (especially plasma triacylglycerol) in middle-aged and elderly subjects, and are really only appropriate for subjects with a high level of physical activity who need to maintain muscle glycogen content. Meals with a high carbohydrate content can lead to problems of postprandial hypotension in the elderly, and impaired exercise capacity in patients with angina.