Macronutrients

Macronutrients are nutrients required by the body in relatively large amounts. In human nutrition, the three main energy-yielding macronutrients are carbohydrates, fats, and proteins. They provide energy and also supply chemical building blocks needed for normal body structure and function .^1,2

The three macronutrients have different roles. Carbohydrates are an important source of metabolic energy. Fats provide energy and are components of cell membranes and other biological molecules. Proteins supply amino acids used to build and maintain body proteins, including structural proteins, enzymes, transporters, and signaling molecules. Using conventional food-energy values, digestible carbohydrate and protein provide about 4 kilocalories per gram, while fat provides about 9 kilocalories per gram .^1,2

Macronutrients are distinguished from micronutrients mainly by the quantities in which they are required. Vitamins and minerals are micronutrients because they are needed in much smaller amounts and do not themselves provide energy. The terms do not indicate relative importance, since both macronutrients and micronutrients are necessary for normal physiological function .¹

Water is also required in large quantities but does not provide energy, so it is usually treated separately from the three energy-yielding macronutrients. Dietary fiber is generally grouped with carbohydrate, although much of it is not digested and absorbed in the small intestine in the same way as digestible carbohydrate .^1,2