Carbohydrate bioavailability

Abstract

There is consensus that carbohydrate foods, in the form of fruit, vegetables and whole-grain products, are beneficial to health. However, there are strong indications that highly processed, fibre-depleted, and consequently rapidly digestible, energy-dense carbohydrate food products can lead to over-consumption and obesity-related diseases. Greater attention needs to be given to carbohydrate bioavailability, which is determined by the chemical identity and physical form of food. The objective of the present concept article is to provide a rational basis for the nutritional characterisation of dietary carbohydrates. Based on the properties of carbohydrate foods identified to be of specific relevance to health, we propose a classification and measurement scheme that divides dietary carbohydrates into glycaemic carbohydrates (digested and absorbed in the small intestine) and non-glycaemic carbohydrates (enter the large intestine). The glycaemic carbohydrates are characterised by sugar type, and by the likely rate of digestion described by in vitro measurements for rapidly available glucose and slowly available glucose. The main type of non-glycaemic carbohydrates is the plant cell-wall NSP, which is a marker of the natural fibre-rich diet recognised as beneficial to health. Other non-glycaemic carbohydrates include resistant starch and the resistant short-chain carbohydrates (non-digestible oligosaccharides), which should be measured and researched in their own right. The proposed classification and measurement scheme is complementary to the dietary fibre and glycaemic index concepts in the promotion of healthy diets with low energy density required for combating obesity-related diseases.