nutrition: Vitamins, Minerals, and Water

Vitamins, Minerals, and Water

To keep the body functioning properly it is necessary to have, in addition to the basic foods, a sufficient intake of accessory substances such as vitamins, minerals (see mineral, dietary), and enough water to carry nutrients to the tissues and waste products away from them. A minimum of about 2 liters of liquid per day are recommended for the average adult. Vitamins function as coenzymes in important body processes, with the exception of vitamin D, which is synthesized upon exposure to sunlight. A large variety of minerals are required, some in trace amounts and others, such as calcium and iron, in relatively large amounts. Milk, cheese, and dark, leafy green vegetables are excellent sources of calcium; liver, meat, and egg yolks are good sources of iron. Minerals are vital to the development of teeth and bones (calcium, phosphorus, and fluoride) and to the functioning of a number of the body's metabolic systems. Iron is a necessary part of hemoglobin in the blood; various metals are required in many enzymes; sodium and potassium are essential to maintenance of fluid balance and functioning of the nervous system; magnesium is needed for the normal functioning of nerves and muscles; and iodine is required for thyroid hormone. The usefulness of vitamin and mineral supplements for a person of good health who eats a well-balanced diet continues to provoke debate among health experts.

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