The four fat soluble vitamins, Vitamins A, D, E and K, share certain characteristics, despite their very different roles in the body's physiology. Since they're all stored in organs such as the liver and are released to the blood when your body needs them, you don't have to consume these vitamins every single day. Vitamin deficiency may develop, for example in people who have difficulty absorbing fat. Toxicity can also occur. Both deficiency and toxicity can cause serious medical problems.
Vitamin A
Vitamin A, also known as retinol, is essential for bone growth, tooth development and proper skin functioning. Retinol is a component of the retinal cells that enable you to see in low light conditions. Vitamin A deficiency can cause night blindness, along with skin problems and reduced immunity to diseases. Young children may experience growth difficulties. Severe vitamin A deficiency in the very young is often fatal. Good sources of vitamin A include leafy greens and orange or yellow fruits and vegetables, such as carrots and pumpkins, all of which contain carotene, a substance that is converted to the vitamin A in your body. Fish and liver contain the vitamin itself. Deficiency can develop in people who have difficulty absorbing fat. Toxicity, which can be a result of taking vitamin supplements, can lead to neurological problems and skin disorders.
Vitamin D
Vitamin D is present in fortified milk, fish and eggs, and it's also produced by your own body when you're exposed to sunlight. Vitamin D affects calcium metabolism and bone strength. In children, deficiency can lead to rickets, a disease in which bones are malformed and soft. In adults, vitamin D deficiency can cause osteomalacia, in which the bones are soft and weak. It also can lead to osteoporosis, casing bones to fracture easily, even without significant trauma. Vitamin D deficiency has also been associated with an increased risk of several types of cancers and of some autoimmune conditions. Certain people are considered at risk for deficiency, including breast-fed infants, older adults and people with limited sun exposure, and supplements are recommended in these instances.
Vitamin E
Vitamin E is an antioxidant that protects various cells in the body from being destroyed. The best sources for vitamin E are vegetable oils. It's also found in grains, nuts and seeds. Supplements are apparently not beneficial, and may even be harmful. People who take cholesterol reducing medications and blood thinners need to be especially careful about taking vitamin E supplements.
Vitamin K
Vitamin K plays a role in the formation of blood clots. It can be found mainly in green leafy vegetables. Some is produced by bacteria that grow normally in your intestines. Certain medications, including several types of antibiotics and phenytoin, an anti-seizure drug, can interfere with the absorption and functioning of vitamin K. Vitamin K deficiency can lead to an increased risk of bleeding. Newborns in the United States are routinely given vitamin K to reduce the risk of a brain bleed, even though vitamin K deficiency is rare. If you're taking blood thinners, vitamin K can counteract their action. You'll need to follow your physician's dietary instructions regarding the amount of leafy green vegetables you may eat.
References
- Colorado State University Extension: Fat Soluble Vitamins
- Merck Manuals: Vitamin A - Vitamin Deficiency, Dependency and Toxicity
- MayoClinic.com: Vitamin D
- University of Maryland Medical Center: Vitamin K
- Office of Dietary Supplements of the National Institues of Health: Dietary Supplement Fact Sheet - Vitamin D
Member Comments