Humans require between 40 and 50 essential nutrients in order to function optimally; these nutrients consist of 1) macro-nutrients (carbohydrates, protein/amino acids, fats/lipids); 2) micro nutrients (vitamins and minerals); and 3) miscellaneous nutrients derived from factors such as light, oxygen, water, and fiber.
13 vitamins are necessary for essential metabolic reactions: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B-complex and vitamin C). Water soluble vitamins can only be temporarily stored and furthermore, in limited quantities. Excesses are passed through the urine. Fat soluble vitamins occur in foods that contain fat and can be stored in the body (in the liver or fatty tissue) until needed. So in the end, you actually need that bit of blubber to stay healthy...
Vitamin deficiencies (avitaminosis) can cause various illnesses, e.g. night blindness (vitamin A deficiency), depression (vitamin B3, B6, B12, and folic acid), scurvy (vitamin C), eczema (folic acid, biotin), rickets or osteomalacia/osteopenia/osteoporosis (vitamin D).
"Whatever", you say - you take your multivitamin, so it's covered. Or maybe you knock back capsule cocktails, after a nice long run. Not so fast.
Though the body cannot distinguish between synthetic (laboratory produced supplements) and naturally occurring vitamins, other substances which accompany the vitamin in its natural state make it perform slightly differently than the synthetic vitamin does. Furthermore, recent studies fail to prove significant benefits of vitamin-popping. And lastly, an active lifestyle means that your body needs a steady supply of them throughout the day (especially those that are water soluble) - so short, quick bursts of the stuff at breakfast or before bed isn't the answer. And as no one food can give us all the vitamins we need, a balanced diet is essential. Bottom line: ditch your vitamins and start eating your 5 a day. Nature does it best.
