Vitamin A -- with forms such as retinol and beta carotene -- is needed for many physiological functions, including vision, a healthy immune system, bone and body growth, normal cell development and reproduction. Your body easily stores the fat-soluble vitamin. But your body does not flush out vitamin A daily and can hold too much, leading to potentially harmful side effects.
Types of Vitamin A
Vitamin A can be supplemented in a variety of forms, some of which may not be as toxic as others. According to the Linus Pauling Institute, vitamin A is actually a generic term used to denote other related compounds such as the retinoids and carotenoids. Retinol and retinal are converted to retinoic acid. Collectively known as the retinoids, these compounds can affect gene transcription and often are used in skin treatments. Carotenoids include carotene and beta-carotene, which are converted into vitamin A in the body. The most usable form of the vitamin is retinol, which is often found in nutritional supplements.
Recommended Daily Allowance
The U.S. Food and Drug Administration recommends getting 5,000 IUs of vitamin A; pregnant women should get 8,000 IUs daily. The FDA also states that taking vitamin A in its beta-carotene form is potentially less toxic. For therapeutic purposes, vitamin A doses can range as high as 50,000 IUs, but any high dose therapy should be carefully monitored by a physician.
Hypervitaminosis A
Toxic levels of vitamin A in your body is referred to as hypervitaminosis A. This syndrome can occur both acutely and chronically -- you can overdose in a short period of time, or your body can build up toxic levels gradually. Symptoms are similar in either case. You can experience blurred vision, dizziness, headaches, nausea, low appetite, hair loss, brittle nails, or peeling and yellowing skin. Hypervitaminosis A can also occur in infants and children where bone development is impaired. Abnormal softening of the skull, bulging fontanelles and poor weight gain are characteristics of too much vitamin A.
Prescription Medications
Certain acne treatments, like Accutane, use retinoids in high doses to clear skin. The exact mechanisms of action are unclear, but these prescription medications can have a positive effect on difficult cases of acne. Because these substances form vitamin A, and are given in high doses, they carry risks. Severe birth defects, dry peeling skin and intestinal complications like Crohn's disease can result. Low doses of prescription retionoids are available, and may be less harmful than higher dose medications.
Member Comments