Along with energy and protein, the body needs two further groups of nutrients in the diet, in relatively small amounts: mineral salts and vitamins. ‘Vitamins and minerals’ explains how these micro-nutrients are essential for maintenance of normal health, growth, and metabolic integrity. Vitamin D and niacin are the only vitamins that can be synthesized by the body; all other vitamins must be provided in the diet. The most important minerals are iron and calcium, but other trace elements are required in small amounts. Iron is needed for synthesis of the protein haemoglobin, which transports oxygen in red blood cells, and calcium is required for bone formation and regulating the activity of muscle.