Vitamins
Vitamins are essential nutrients that must either be ingested or synthesised to maintain health. There are two main varieties: water-soluble and fat-soluble. Because some vitamins are only soluble in fat, a totally fat-free diet can be unhealthy.
Vitamin A (also known as retinol) is a fat-soluble vitamin found in dairy products and in liver. Excessive vitamin A can poison you. The body can create vitamin A as needed from beta-carotine , which is water-soluble and not dangerous. (large amounts can turn your skin and eyes orange though) You can get plenty of beta-carotine from carrots, squash, and spinach. Vitamin A deficiency can affect the eyesight, so the popular belief that carrots help you see in the dark is not wholly false.
The Vitamin B group of water-soluble vitamins contains a number of separate vitamins.
Vitamin C (or ascorbic acid) is a water-soluble vitamin found in citrus fruits and green vegetables. A deficiency can lead to scurvy.
Vitamin D (or calciferol) is a fat-soluble vitamin found in oily fish. Humans can also synthesise the vitamin from the effects of sunlight on skin.
Vitamin E (or tocopherol) is a fat-soluble vitamin found in vegetable oils, nuts and green leafy vegetables.