Nutrients that the body requires in very small amounts are called micronutrients. Vitamins and minerals are micronutrients that are needed for thousands of daily body functions. They work together in groups – for example, vitamin D regulates the absorption of calcium, and so both are equally important for maintaining healthy teeth and bones. A lack of any individual micronutrient can lead to ill health, either directly or by reducing the body’s overall resistance to disease.
The micronutrients known as vitamins are organic substances that occur in living tissues; the majority cannot be manufactured by the body and must be obtained from food. Vitamins are usually classified according to whether they are soluble in water or fat. The B vitamins and vitamin C are water-soluble; they cannot be stored by the body and are easily eliminated in urine and sweat, so they need to be replaced on a regular basis. The fat-soluble vitamins A, D, E and K require fat for their absorption into the body. Because these vitamins are not easily excreted, they can accumulate in the body and an excess amount can be hazardous to health.
Each of the vitamins has a specific role to play in the body; vitamin B2, for example, is required in minute amounts to promote cell division and growth.
Minerals and trace elements
Essential for health and growth, minerals perform many important functions in the body, such as the formation of bones and teeth, maintaining a healthy immune system, and helping vitamins to do their work. Once their work is done, minerals are excreted from the body in urine and perspiration, and therefore need to be replaced regularly.
Macro-minerals, such as calcium and potassium, are required in comparatively large quantities. Micro-minerals, such as iron and zinc, are needed in much smaller amounts. Some minerals, such as selenium, magnesium and iodine, are required in such miniscule amounts that they are known as ‘trace elements’.
Because plants cannot manufacture their own minerals, and have to extract them from the earth, the levels of minerals found in foods depend on the amounts present in the soil where plants were grown, or where animals grazed.
The body can maintain its own mineral balance over short periods of time, but if the intake gets low, it draws from stores laid down in the muscles, the liver and even the bones. If mineral intake is too high, any excess is usually excreted.