Nutrients, Vitamins and Minerals

The nutrients in food fall into two broad groups by the quantity the body needs: macronutrients — carbohydrates, proteins and lipids — required in relatively large amounts, and micronutrients — vitamins and minerals — required only in small amounts. Both groups can include essential nutrients that the body cannot manufacture for itself and so must obtain from the diet; water, too, plays an essential metabolic role and prevents dehydration, even though it supplies no calories. Eating too much or too little relative to the body's real requirement is called malnutrition, while a balanced diet supplies carbohydrates and fats for energy, proteins for growth and tissue replacement, and vitamins, minerals and water for regulating the body's physiological processes. Vitamins are organic substances needed in minute amounts as metabolic regulators; they split into the fat-soluble group (A, D, E and K, listed with their functions and deficiency diseases in Table 1) and the water-soluble group (the B-complex vitamins and vitamin C, in Table 2). Because the fat-soluble vitamins can be stored in the body, consuming them in excess can itself cause harm — a condition called hypervitaminosis — which is not generally a risk with the water-soluble ones, since any excess is simply excreted. Minerals are inorganic elements such as calcium, iron, iodine, potassium, magnesium, sodium, phosphorus and sulphur, needed to regulate a wide range of physiological functions; they are grouped …