Vitamins are essential nutrients that the human body can not synthesize and must ingest them through food. Vitamins arise from plants with the help of the sun and/or bacteria and from human or animal body.
There are about 40 different substances known as essential nutrients in the human diet. 13 of them were identified as vitamins, 15 were identified as essential minerals, minerals in traces and electrolytes. The other 12 are amino acids. Vitamins are divided into two basic groups:
1. Water-soluble vitamins - this group includes B-complex and vitamin C. These vitamins are easily absorbed directly through the gastrointestinal tract into the blood. When absorbed, they circulate through the body and are prepared for the needs of the organism. Most water-soluble vitamins is not stored in the body in large quantities over a long period. When the concentration exceeds a certain amount, the body expels them out through urine. In these moments, the urine is white, unlike the normal yellow color of urine.
2. Fat-soluble vitamins - they dissolve in fat, and are stored in fatty tissues. These vitamins require additional substances, emulsifiers, so they can be converted into a chemical compound that can be absorbed into the blood. When it is absorbed, fat-soluble vitamins travel to place in the body where it places for the needs of the organism.
Vitamin deficiencies are rare among people who have access to a wide variety of foods and know how to put together a balanced diet.
Some vitamins are toxic when taken in the very large amounts known as megadoses. Megadoses of vitamin A (as retinol) may cause symptoms that make you think you have a brain tumor. Taken by a pregnant woman, megadoses of vitamin A may damage the fetus. Megadoses of vitamin D may cause kidney stones and hard lumps of calcium in soft tissue (muscles and organs). Megadoses of niacin (sometimes used to lower cholesterol levels) can damage liver tissue. Megadoses of vitamin B6 can cause (temporary) damage to nerves in arms and legs, fingers, and toes. The likeliest way to get a megadose of vitamins is to take supplements.