Vitamins are a group of totally unrelated chemicals that have only one thing in common; they are essential (usually in tiny amounts) for the normal function of the body.
Vitamin A is found in milk, butter, eggs, fish, liver and most fruits and vegetables; with very high levels being found in orange colored foods (eg: carrots, paw paw. pumpkin etc).
It is essential for the normal function of the skin and eyes, but there is no evidence that Vitamin A can improve vision in people with sight problems due to other diseases, or cure skin problems.
High doses taken as fruit or vegetables may cause the disease carotenemia; but overdosage with prepared Vitamin A supplements is quite serious and may cause foetal abnormalities in pregnant women, and signs of increased pressure on the brain.
Vitamin B1 is found in liver, kidney, whole grain and lean pork; and is essential for the breakdown of foodstuffs.
It is almost impossible to have a lack in only one of the Vitamin-B groups. If one is missing, all will be missing. They may be lacking in fad diets and with the overcooking of foods.
Excess intake of the vitamin is rapidly excreted through the kidneys and high doses have no serious side effects.
Vitamin B2 is found in dairy products, leafy vegetables and offal; and is essential for the effective working of the lungs. A severe lack is rare, and overdosage is not harmful.
Vitamin B6 is used in the breakdown of protein foods, and low levels may cause anaemia and other blood diseases.
It is used in medicine to relieve nervous tension, treat mouth inflammation, ease pre-menstrual tension, and may help hardening of the arteries. Its level may be reduced by oral contraceptives.
Vitamin B12 is found in most meats and a lack causes pernicious anemia in which the vitamin must be replaced by regular injections.
Vitamin C is found in citrus fruits, tomatoes and leafy green vegetables; but its level in food is reduced by cooking, mincing and contact with copper utensils.
It is essential for the formation and maintenance of cartilage, bone and teeth. It is used in moderate doses to promote healing of wounds and ulcers and during convalescence from prolonged disease. There is no evidence to support its use in preventing or treating the common cold, despite many exhaustive trials.
Excessive doses of Vitamin C can be dangerous (particularly in children) causing skin rashes, diarrhea, heartburn, reduced fertility and kidney stones. It may also interfere with laboratory tests.
Vitamin D is a chemical found in egg yolks and butter, or may be formed by a reaction of sunlight on the skin. It is essential for the balance of calcium and phosphorus in the body and a severe lack may cause bone diseases.
Excessive doses of Vitamin-D preparations can cause severe kidney damage and the hardening of tissue. It is not routinely used in the treatment of disease.
Vitamin E is readily available in most foods. Very high doses may cause many serious diseases and abnormalities including blood clots, high blood pressure, breast tumors and headaches. It is a quite dangerous drug and the only medical uses are in premature infants and in some rare diseases.
Vitamin K is essential for the clotting of blood. It is found in most foods, and is also made by bacteria that normally live in the gut. A lack is very rare, but may occur if the absorption of fat from the gut is abnormal.
High doses may cause severe anemia and death in infants. In adults it can cause the breakdown of blood. It is not used to treat any diseases.
Nicotinic acid (Niacin) is found in peanuts, liver, yeast, meat and whole grains, and an acute lack causes the disease pellagra. It is used in certain types of headache, nervous disorders, muscle pains, balance disorders and blood diseases.
Large doses may cause flushing and dizziness, but are not otherwise harmful.
Folic acid is essential to the basic function of cells, and extra amounts are often required in pregnancy, breast feeding and certain types of anaemia.
The level of folic acid may be low in alcoholics, and supplements may also be needed in some people taking epilepsy drugs and oral contraceptives.
Generally, there is no evidence that vitamin supplements benefit anyone on a normal diet and in good health. There are certain diseases where some vitamins can be beneficial, but others may be quite dangerous in high doses.
Normally, the cheapest and most effective way to obtain adequate vitamins is to eat a well-balanced diet. Most vitamin supplements are very expensive, and usually pass rapidly through the body to enrich our sewers.