Fat Soluble Vitamins

Most of the vitamins were discovered from the years 1900 to 1950. It was found that a fat-soluble factor prevented xerophthalmia (dry eye disease) in rats, and the discoverers called it fat-soluble A factor. This factor is now known as vitamin A or retinol. Soon other fat-soluble factors (the fat-soluble vitamins A, D, E and K) were discovered.

Although the four fat-soluble vitamins ( A, D, E and K ) differ in function,. utilization, and sources, they also have several similar characteristics. They are soluble in fat and fat solvents; are fairly stable to heat, as in cooking; do not contain nitrogen; are absorbed in the intestine along with fat and lipids in foods; and require bile (greenish brown liquid to help the body to deal with fats) for absorption.

The fat-soluble vitamins A, D, E and K differ from the water-soluble vitamins in several ways. The fat-soluble vitamins are found in the fats and oils of food. They 'are insoluble in water, so they require bile for absorption. The fat-soluble vitamins are stored in the liver and adipose tissue (fatty tissue) until they are needed. They are not readily excreted from the body as most of the water-soluble vitamins are. Vitamins A and D are stored in large amounts for long periods of time and need not be consumed everyday. A person only needs to ensure that their average daily intake should be close to the recommended amount. Because the fat-soluble vitamins can be stored in the body, the risk of toxicity in case of fat-soluble vitamins is greater than it is for the water-soluble vitamins.