Scanning electron micrograph (SEM) of crystals of Vitamin C (ascorbic acid) showing the monoclinic crystal structure. Vitamins are compounds required for the normal functioning of metabolism, but which are not synthesised by the body, so must be obtained from the diet. Vitamin C is most easily acquired from fruit and vegetables. The average adult requirement is 70-100mgs/day. Ingestion of 1-5gm/day has been suggested as a prophylactic against colds. There is little evidence to support this. The excess is eliminated in the urine, and ascorbic acid is partially metabolised to oxalate, so heavy consumption may lead to the formation of urinary stones. Vitamin C deficiency in the diet can eventually lead to the disease scurvy, once common amongst seafarers. It is due to a failure in the metabolism of collagen, an important component of connective tissue. Magnification: X 12 at 35mm size.