Our bones and teeth contain large amounts of calcium. An adult has a total of about 1 kg of calcium and a baby has about 30g in their bones. So, during the period of growth from a baby to an adult, a large amount of calcium has to be added to the bones. Therefore, doctors prescribe calcium tablets to children and pregnant women. Calcium is always present in the body in combination with another mineral. phosphorus. Milk and green leafy vegetables are a very good source of calcium. It is also required for proper working of muscles and for . clotting of blood. Another important mineral is iron which is required for making haemoglobin in the blood. Haemoglobin gives red colour to the blood. In comparison to 1 kg of calcium, the total amount of iron in the body is about 3 g. Iron is necessary for growing children and pregnant women. During the menstrual period, women lose iron and therefore, they need extra iron. Fig shows various food rich in iron. About 17 different minerals are necessary for healthy functioning of our body, though their amount is insignificant in comparison to the bulk of food taken by us. Hence, these minerals are often referred to as "micronutrients". Some of these minerals are constituents of the body cells and the body fluids, and as such take part in chemical reactions in the cells. Have you heard of fluoride toothpastes? Fluorine is essential to produce strong teeth that resist decay.