Vitamin A is an essential vitamin that helps maintain your overall health and the normal function of your eyes, your immune system and several other organ systems. It is especially important during pregnancy and in infants and children. A deficiency in vitamin A can cause serious illness but ingesting too much can be toxic and lead to major problems. Consult your doctor to determine if you should take extra vitamin A and, if it is advisable, to determine the correct amount.
Vitamin A is a group of dietary, fat-soluble compounds, collectively called retinoids. Animal-based foods contain retinoids, while plant-based foods contain pigments called carotenoids, precursors that your body converts into vitamin A. Vitamin A is extremely important for many biological processes, especially during development. It also has a vital function in your eyes, where special receptors in your retina use it to manufacture a light-responsive molecule. Vitamin A also helps keep your cornea and skin healthy and is important for the membranes that line your digestive and respiratory systems. It also supports your immune system, helping you to avoid illness and resist infection.
Failure to ingest enough vitamin A or its precursors can lead to serious health problems. Vitamin A deficiency is especially harmful to vision and is the most common cause of blindness in children worldwide, according to the World Health Organization, which says that up to 500,000 children lose their sight yearly due to vitamin A deficiency. A vitamin A-deficient diet can also cause an eye condition called xeropthalmia, a disorder in which low production of tears causes dryness of the eyes' membranes and, if uncorrected, corneal damage that can interfere with vision.
If a woman fails to consume sufficient vitamin A or its precursors during pregnancy, the risk to her health and that of her fetus increases significantly, especially during the last trimester when the fetus grows quickly. Because vitamin A is critical for proper growth of organs and tissues, a deficiency may lead to serious developmental problems in the fetus or even cause fetal death. Vitamin A deficiency can also cause night blindness in pregnant women, a condition in which the retina functions poorly in low-light conditions. A nursing infant is at increased risk for illness if his mother does not ingest sufficient vitamin A while she is lactating.
A deficiency in vitamin A raises the likelihood of developing other health problems, including skin conditions, diarrhea and respiratory disorders. Because it supports normal function of the immune system, a lack of vitamin A can also lead to poor recovery from infections. This is especially true for children, who may have difficulty overcoming common illnesses such as measles if they fail to consume enough vitamin A or its precursors.
The recommended dietary allowance for vitamin A differs with age, ranging from 300 micrograms daily for children aged 1 to 3 to 900 micrograms daily for adults. Although vitamin A supplements are available, do not consume these without first consulting your doctor, since excess vitamin A can produce headache, fatigue, joint pain, liver failure and even death. Because your body converts carotenoids into vitamin A as needed, you can safely increase the availability of vitamin A to your body by consuming abundant carotenoid-rich, orange and yellow foods such as carrots, oranges, sweet potatoes, pumpkin, apricots and peaches.
- Office of Dietary Supplements: Vitamin A
- MayoClinic.com: Vitamin A (Retinol)
- Elmhurst College Virtual Chembook: Beta-Carotene and Vitamin A
- World Health Organization: Vitamin A Deficiency
- Harvard School of Public Health: Vitamin A
- University of Maryland Medical Center: Retinol (Retinol)
- Medical Dictionary: Xeropthalmia
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