The Absorption Of Fat-soluble Vitamins

Vitamins are important for many functions in the body such as growth, digestion and nerve function, and are found in many types of foods. There are water-soluble and fat-soluble vitamins, with the latter type lasting much longer in the body due to its storage in the liver and fatty tissues. It is the fatty tissue cells that assist in the absorption of fat-soluble vitamins into the body.

About Fat-Soluble Vitamins

The fat-soluble vitamins include vitamins A, D, E and K. Vitamin A is important for the health of the skin, eyes, and mucous membranes as well as for bone and tooth development. Vitamin D is important for the health of bones and teeth since it assists in the absorption of calcium that helps with the integrity and strength of such body structures. Vitamin E, like vitamin A, is an antioxidant and thus prevents damage to cell membranes. Vitamin K is important in the clotting of blood; therefore a deficiency of vitamin K can cause excessive bleeding.

Recommended Fat-Soluble Vitamin Intakes

Fat-soluble vitamins can be consumed less frequently and in smaller amounts due to the ability of such vitamins to be stored in the body for later use. Therefore, it is important not to ingest megadoses of such vitamins in supplemental form since toxicity, especially of vitamins A and D, could cause nausea, vomiting, weakness, or other severe symptoms, according to the Food and Drug Administration. The Institute of Medicine's daily recommended intakes of fat-soluble vitamins for most individuals are 700 to 900 micrograms (mcg) of vitamin A, 600 international units of vitamin D, 15 mg of vitamin E, and 90 to 120 mcg of vitamin K, with lesser amounts recommended for children. Vitamin A can be found in liver, dairy products and orange fruits and vegetables, vitamin D can be found in fortified dairy products and fish oils, vitamin E can be found in whole grain foods and nuts, and vitamins A, E, and K can all be found in leafy green vegetables such as spinach, kale and collard greens.

Absorption of Fat-Soluble Vitamins

According to the Centers for Disease Control, the absorption of fat-soluble vitamins from the gastrointestinal tract depends on those processes responsible for absorption or metabolism. Fat-soluble vitamins are absorbed into the body through bile acids released by the liver, which are substances used in the digestive process to absorb fat from the foods we eat.

Factors Affecting Absorption

Any disorder that involves malabsorption of fat can affect the absorption of fat-soluble vitamins. Disorders such as celiac disease, Crohn's disease and pancreatic disorders can affect the absorption of fat-soluble vitamins. Deficiencies of fat-soluble vitamins are rare, but if present may cause defects in the bones, teeth and skin as well as negative effects on immune and nerve function. Deficiencies of fat-soluble vitamins can be corrected with consumption of fat-soluble vitamin-rich foods or vitamin supplementation.