Alternative Names retinol, retinal, retinoic acid, carotenoids including beta-carotene
Definition Vitamin A is a fat-soluble vitamin meaning it is able to be dissolved in fat. Vitamin A is carried throughout the body by fat. The body can store fat-soluble vitamins. Getting too much can be harmful.
What food source is the nutrient found in? Vitamin A, in the form of retinal or retinol, comes from animal sources. These include liver, eggs, full cream milk and the oils of some fish. Vitamin A, in the form of carotenoids, is found in plants. Carotenoids such as beta-carotene, are converted 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. It is also found in many dark-green leafy vegetables. Some of these include:
How does the nutrient affect the body? Vitamin A helps build and maintain healthy teeth, skeletal and soft tissue, skin and mucous membranes. It helps the growth and health of all cells in the body. It is especially important for proper night vision. Vitamin A plays an important 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. An accumulation of free radicals can damage body cells and tissues.
Information Vitamin A is usually measured in retinol equivalents (RE). The Recommended Dietary Intake (RDI) for vitamin A for adults is 750 mcg RE per day. There is no increase of vitamin A requirements during pregnancy but lactating women need about 450 mcg RE more per day.
Vitamin A can be stored in the fatty tissues of the body. This can pose a problem for people taking high doses of vitamin A in the form of supplements. High doses can be toxic and cause symptoms such as headaches, dry and scaly skin and liver damage. It can also cause:
bone and joint pain
vomiting or lack of appetite
abnormal bone growth
Generally, levels 10 times the RDI (far more than a person could get through diet alone) have been linked with these symptoms. Vitamin A can only reach toxic levels if a person is taking supplements. Do not exceed 3000 mcg in children or 7500 mcg in adults of vitamin A. 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.
Just as high doses of vitamin A are a problem, getting too little can have side effects too. Symptoms of significant deficiency include:
lowered resistance to infections
problems with reproduction
improper tooth formation
rough, dry and pimply skin
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 dairy products to ensure optimal intake of vitamin A.
Author: Clare Armstrong, MS, RD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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