Vitamins A, D, E and K are classified as fat-soluble vitamins, which do not dissolve in water and are absorbed by fat and transported throughout the body. According to Colorado State University Extension, deficiencies of fat-soluble vitamins are uncommon, since they are stored in the liver and the fatty tissues. Unlike water-soluble vitamins, which are eliminated in urine in excess quantities, toxicities in fat-soluble vitamins may occur at mega doses.
Vitamin A
Vitamin A has many crucial roles in the body. It is involved in low light vision, reproduction, cell development, bone growth, immune system regulation and the production of white blood cells, according to the Office of Dietary Supplements of the National Institutes of Health. Vitamin A is found in different forms. Animal sources of vitamin A are in the form of retinol, which is considered to be one of the most usable forms of vitamin A. Retinol is found in liver, eggs, milk and cheese. Plant sources of vitamin A are in the form of carotenoids, most commonly beta-carotene, which is found in carrots, cantaloupes, sweet potatoes and spinach. The body doesn't absorb Vitamin A from plant sources as well as it absorbs the vitamin from animal sources.
Vitamin D
Vitamin D is often referred to as the sunshine vitamin. According to MayoClinic.com, as little as 10 minutes of sunlight daily may help to prevent deficiencies of vitamin D, depending on factors such as latitude, skin pigment and sunscreen use. Vitamin D is also found in milk, fish and eggs. The vitamin helps your body absorb calcium, and it aids in the development and maintenance of strong bones. MayoClinic.com also reports that research shows that vitamin D may provide protection from other diseases and conditions, including cancer, autoimmune conditions and high blood pressure.
Vitamin E
Vitamin E is essential for the development of red blood cells. It is an antioxidant that protects vitamins A and C. Vitamin E deficiencies are rare. The vitamin is found in corn, nuts and olives, as well as in vegetable oils such as corn, sunflower and soybean. High doses of supplemental vitamin E may affect the metabolism of certain medications like blood thinners, according to the Office of Dietary Supplements. Consuming a balanced diet is the best way to meet your vitamin needs.
Vitamin K
Vitamin K plays a primary role in blood clotting. As a result, a vitamin K deficiency can lead to excessive bleeding. Vitamin K is also important in promoting healthy bones. The most common sources of vitamin K are dark green leafy vegetables such as broccoli, kale, spinach and cabbage. The vitamin is also produced naturally by the bacteria in your digestive tract. If you are taking anticoagulant medications, you should maintain a consistent level of vitamin K for optimal drug effectiveness.
References
- Office of Dietary Supplements: Dietary Supplement Fact Sheet: Vitamin A and Carotenoids
- MayoClinic.com; Vitamin D; Dec. 1, 2010
- MedlinePlus; Vitamin E; updated by Linda Vorvick, MD; March 7, 2009
- Office of Dietary Supplements: Dietary Supplement Fact Sheet: Vitamin E
- University of Maryland Medical Center; Vitamin K; reviewed by Steven D. Ehrlich, NMD; June 18, 2009
- Colorado State University Extension; Fat-Soluble Vitamins; J. Anderson and L. Young; Aug. 2008
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