Vitamin A

Alternate Names : Retinol, Retinal, Retinoic Acid, Carotenoids Including Beta-Carotene

Vitamin A is a fat-soluble vitamin which means it can be dissolved in fat. Vitamin A is carried through the body by fat. The body can store this type of vitamin in fat tissue. Getting too much can be harmful.

Information

Vitamin A is usually measured in retinol equivalents, also called RE. The Recommended Dietary Allowance, called RDA, for vitamin A for adult men, from age 11 on, is 1,000 RE per day. Women, from age 11 on, should get 800 RE per day. There is no increase of vitamin A requirements during pregnancy but lactating women need about 500 RE or more per day.

Vitamin A can be stored in the fat tissues of the body. This can pose a problem for people taking extra doses of vitamin A. High doses can be toxic and cause symptoms such as the following:
headaches
dry and scaly skin
liver damage
bone and joint pain
vomiting or lack of appetite
abnormal bone growth
nerve damage
birth defects

In most cases, only levels 10 times the RDA (far more than a person could get through diet alone) have been linked with these symptoms. Vitamin A cannot reach toxic levels unless a person is taking extra doses. Carotenoids are not converted to vitamin A fast enough to increase the amount of vitamin A stored in the body. Beta-carotene is NOT toxic to the body.
Getting too little vitamin A can cause side effects too.
Symptoms of significant deficiency include:
lowered resistance to infections
problems with getting pregnant
poor growth
improper tooth formation
rough, dry, and pimply skin
digestive problems
night blindness
eye disease, including xerophthalmia (zear-off-thal-me-ah), a condition in which the clear covering of the eye known as the cornea becomes dry and dull

Vitamin A is an important fat-soluble vitamin. Eat a variety of fruits, vegetables, lean meats, and fortified dairy products to ensure optimal intake of vitamin A. Read food labels to help choose foods with vitamin A content.
Source
http://www.healthopedia.com/vitamin-a/