Friday, May 7, 2010

Vitamin A

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.

What food source is the nutrient found in?
Vitamin A can come from animal sources such as:

* eggs
* fortified milk
* liver
* oils of some fish

This form of Vitamin A is called retinal or retinol.

Vitamin A is also found in plants. This form is called carotenoids. Substances such as beta-carotene are converted from carotenoids into vitamin A in the body. Beta-carotene is one of the most common carotenoids. Carotenoids are pigments found in deep orange, red, and yellow fruits and vegetables. They are also found in many dark-green leafy vegetables, such as:

* carrots
* pumpkin and other squashes
* sweet potatoes
* cantaloupe
* broccoli
* spinach

How does the nutrient affect the body?
Vitamin A helps develop and maintain healthy growth in the cells and almost all the parts of the body. It is especially key for proper night vision, but is also needed for the health of a person's:

* teeth
* skeletal and soft tissue
* skin
* mucous membranes

Vitamin A plays a key role in the immune system by helping protect from infections. Beta-carotene is an antioxidant. It has been studied for its role in cancer and heart disease protection. Antioxidants help fight free radicals. Free radicals are oxygen by-products produced when body cells burn oxygen. A build up of free radicals can damage body cells and tissues.

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

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