VitaminsFood contains only small quantities of vitamins, but they are vital for good health. For example, if you eat a diet of meat, bread, sugar and fat, you may become ill with a disease called scurvy (坏血病). This is caused by a deficiency （缺乏） in vitamin C, which is found in fruit and vegetables.About fifty different vitamins have been identified, and a deficiency in many of these can lead to illness. Vitamin A is most important for good eyesight, but is also important for general good health. Liver contains a considerable amount of vitamin A, but vitamin A is also found in fish, meat, milk, butter, some fruits and vegetables,Vitamin B in fact consists of twelve different chemicals, which are found in eggs, cheese, butter, wholemeal flour and vegetables. If a person has not enough vitamin B in his diet, this may affect his whole body, particularly the skin, the nervous system and the heart.Vitamin C prevents scurvy and helps to heal injuries. Some doctors believe that large quantities of vitamin C help people to avoid colds. Fruits and uncooked vegetables are rich in Vitamin C, but when they are overcooked, or left for a long time, they lose most of their vitamins.Vitamin D is essential for the growth of bones and teeth and is found in fish, liver, oil and milk. Vitamin D is the only vitamin which the body can make for itself, but it can only do this if there is sufficient sunlight. A lack of both sunlight and vitamin D can result in a disease called rickets (佝偻病) ， which causes bones to soften and to be deformed.Vitamins are only needed in very small quantities. A quantity sufficient for a whole life would weigh only a quarter of a kilogram. Vitamins can be manufactured and are sold as additions to our food, but a well-balanced diet will provide an adequate amount of vitamins.
Vitamin C is used by doctors to heal the diseases of nervous system.