A healthy high quality diet should be composed of fat, protein and carbohydrate. All of these components should be of high quality which means that the protein should contain all the essential amino acids in the right proportions for human health, the fat should contain both of the essential fatty acids in the right ratios and also provide long chain marine oils, and the carbohydrates should be unrefined and as close to their original plant form as possible. Good sources of carbohydrates include whole grains and legumes, and both provide excellent high quality nutrition which suggests that they should both incorporated into a healthy high quality diet. Both provide high quality fibre, a range of vitamins and minerals, as well as phytonutrients that may have beneficial health effects, particularly in terms of providing antioxidant defences. However, when considering the diet as a whole, there is good reason to favour legumes over grains as the cornerstone of a healthy eating plan.
The two main differences between the nutritional content of legumes and whole grains is that the former contains higher levels of protein and higher levels of soluble fibre that falls into the categories of gum fibre. The high protein content of legumes may explain some of their weight loss effects, as high protein diets have been shown to have beneficial effects on satiety and postprandial glycaemia. These effects may interact to cause a shift in metabolic regulation that favours weight loss. The fibres in legumes are interesting because they can form highly viscous barrier layers along the enterocytes and in this way may enhance the beneficial glycaemic effects of the high protein content which mechanistically may work through delaying gastric emptying. Legumes then have far more favourable effects on postprandial glycaemia compared to whole grains. Both whole grains and legumes are important parts of a healthy diet, but the lower glycaemic index of most legumes means that a high quality diet should favour the latter.
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