Types of Fat-Soluable Vitamins
- Fat-soluble vitamins, which dissolve in fats or lipids, can be obtained from the lipid portion of vegetable and animal sources. They are absorbed in the intestine and stored in the human body until they are needed. This can result in toxicity if over-consumed..
- Each fat-soluble vitamin has a unique role. Vitamin A protects cells from toxic substances, supports the immune system, promotes healing and growth of tissues such as the skin, and helps the eye function properly. Vitamin D is necessary for calcium and phosphorus metabolism, which in turn are important for bone growth and maintenance. Vitamin E protects cells from damage by stabilizing cell membranes and removing toxic free-radicals. Vitamin K participates in blood-clot formation.
- The fat soluble vitamins are found only in lipids so they are prevalent in foods with high lipid contents such as liver, fish liver oil, nuts, grains, dairy products and egg yolks. Vitamin K is found in most green plants, polyunsaturated oils, blackstrap molasses and yogurt. Additionally, the bacteria in the intestine make some vitamin K. The best sources of vitamin E are vegetable and seed oils. Vitamin D is made when the skin comes in contact with UV light or can be obtained from fish, milk, egg yolks or liver. Yellow or orange colored fruits and vegetables (i.e. carrots and pumpkin) are a good source of vitamin A.
- Since fat-soluble vitamins are stored in the body, any excess intake can result in illness from toxicity. Vitamin A is most likely to cause toxicity as it is not quickly excreted by the body. An excess of vitamin A from food sources or supplements can lead to swelling of the brain, stomach upset, enlarged liver, dry skin or stunted growth. Although less common, vitamins E, D and K can also produce toxicity if consumed in excess.
- An insufficient intake of fat-soluble vitamins can result in a deficiency disease. Because fat-soluble vitamins can be stored in the body, however, deficiencies of these vitamins are uncommon. Fat-soluble vitamin deficiencies are most likely to occur in individuals with extremely poor nutrition, intestinal absorption issues, liver disease or metabolic dysfunction. The daily Recommended Dietary Allowance (RDA) of fat-soluble vitamins is a very small quantity, measured in micrograms.