Fat-soluble vitamins necessary to the human body as well as other mammals for daily repair and functioning of body organs.[1] These are vitamins that are stored in body fat and also dissolve in body fat as opposed to water-soluble vitamins which dissolve in water and are not stored in the body.
The fat soluble vitamins are absorbed from the terminal ileum, and so pathology at this location can lead to their deficiency (e.g. ileal resection, Crohn's disease). They can also become deficient in poor diets, malabsorption (e.g. cystic fibrosis) and obstructive jaundce (bile is required in the duodenum/ileum to facilitate fat absorption).
Fat soluble vitamins are mostly found in fatty foods and fish-liver oils and are particularly rich in vitamins A and D. A certain amount of fat is needed in the diet to help the body absorb these vitamins. Vitamins A and D are also found in human liver and if the diet contains more vitamin A or D than is immediately required the surplus is stored in the liver. Enough of these vitamins is stored in the liver of a well-nourished person to satisfy the body's needs for several months if they are absent from the diet. If the diet contains too much vitamin A or D, however, the surplus will accumulate in the liver and may be harmful. Such excessive intakes are less likely to result from over-eating than through over-enthusiastic use of vitamin pills or dietary supplements.