Vitamin A is essential to the proper functioning of your eyes. Involved in both low-light and color vision, vitamin A is converted by your body into retinal, a molecule that helps your retinas to absorb light. Found in a variety of plant and animal sources, vitamin A concentrations are particularly high in such foods as carrots, liver and butter. Due to being readily available in numerous food sources, the use of supplements can potentially lead to overconsumption of vitamin A.
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Vitamin A derived from animal sources is the most easily used by your body. Known as preformed vitamin A, animal-source vitamin A enter your body as retinol. As retinol is easily converted to retinal, preformed vitamin A is the most biologically available source of this essential vitamin. When derived from non-animal sources, vitamin A is known as provitamin A carotenoid. Found in high concentrations in colorful and green, leafy vegetables, provitamin A carotenoid is most commonly derived from beta-carotene, alpha-carotene and beta-cryptoxanthin. Although others exist, your body is able to produce vitamin A from fewer than 10 percent of all known carotenoids. Of these forms, beta-carotene is the most readily converted to retinol, producing approximately twice the retinol as would be made from a similar amount of alpha-carotene or beta-cryptoxanthin.
Aside from its important role in vision, vitamin A is involved in bone growth, reproduction, cell division and cell differentiation, or the process by which cells become assigned to different parts of the body. In addition, vitamin A plays numerous roles in the immune system. These include helping lymphocytes to fight off infection, maintaining surface linings of organs that prevent the entry of harmful bacteria into the body and promoting the healthy development of the skin and mucous membranes.
Acute Hypervitaminosis A
Despite the numerous benefits of vitamin A, there are risks associated with overconsumption of this essential vitamin. Known as hypervitaminosis A, having too much vitamin A in your body can lead to a range of adverse symptoms. The two forms of hypervitaminosis A are acute and chronic, referring to the underlying cause of these high levels. Acute hypervitaminosis A occurs when too much vitamin A is taken at one time. Generally associated with overconsumption of supplements, acute hypervitaminosis A can lead to the formation of rashes, headaches, increased pressure in your skull, drowsiness, nausea, vomiting, irritability, blurred vision, stomach pains and a lack of muscle coordination. The symptoms associated with acute hypervitaminosis A pass once the excessively high levels of vitamin A have left your body, provided you do not continue ingesting vitamin A.
Chronic Hypervitaminosis A and Carotenemia
Chronic hypervitaminosis A occurs when you consistently have excessive amounts of vitamin A in your body, often due to daily oversupplementation. This condition arises solely as a result of overconsumption of preformed vitamin A, as the conversion of provitamin A carotenoids to vitamin A is closely regulated by your body. Overingestion of carotenoids is possible, and leads to a generally harmless condition know as carotenemia. While overuse of supplements is the most common cause of this chronic hypervitaminosis A, this disorder can also arise from treatments for acne and other skin conditions. Despite the risks of hypervitaminosis A, many popular and effective skin treatment products include or rely on extremely high concentrations of vitamin A. As such, it is important that you consult with your doctor before beginning any treatment program for acne or other skin disorders.
Symptoms of Chronic Hypervitaminosis A
In contrast with carotenemia, chronic hypervitaminosis A is associated with a range of adverse effects. Immediate effects include hair loss, dry, rough skin and hair, dry eyes and cracked lips. If early symptoms are not treated, this condition can lead to severe headaches, feelings of weakness, liver abnormalities, reduced bone mineral density and osteoporosis, central nervous system disorders and birth defects in children of pregnant women. As these symptoms can cause severe damage to your health, monitor your daily vitamin A intake and consult your doctor if you believe that you are suffering from hypervitaminosis A.