Vitamin A is stored in the fat tissues of your body, and plays several important roles in physical function. This vitamin binds to opsin, a protein that enables the detection of images in low light, according to the Linus Pauling Institute at Oregon State University. It also increases the availability of iron to developing red blood cells, which aids in the formation of hemoglobin.
Daily Requirements
Requirements for vitamin A are largely dependent upon age and gender. The daily requirement of vitamin A is 700 mcg for female adolescents and adults, and 900 mcg for male adolescents and adults, according to the University of Maryland Medical Center. Pediatric requirements range from 400 mcg daily for infants to 600 mcg for children between the ages of 9 and 13. Breastfeeding females should consume between 1,200 and 1,300 mcg of vitamin A daily.
Sources
Vitamin A is available in two forms. Retinyl palmitate is found in animal-based foods such as eggs, whole-milk products, fish oil and chicken, beef and calf liver. Carotenoids, which are substances that your body converts into vitamin A, are primarily found in plant-based foods. These foods include pumpkin, winter squash, kale, spinach, mangoes, sweet potatoes and carrots. This vitamin is available in supplement form, and is commonly included in multivitamin supplements.
Uses
Vitamin A may aid in the prevention of several health conditions. This vitamin is necessary for proper bone development and may play a role in preventing osteoporosis, according to the University of Maryland Medical Center. Vitamin A is also an antioxidant that may help prevent esophageal, breast and cervical cancer, although evidence of this vitamin's role in cancer prevention is not conclusive. This vitamin may also prevent night blindness and the formation of cataracts.
Toxicity
Although vitamin A is important for physical function, overconsumption of this vitamin may increase your risk of toxicity. Daily doses of more than 3,000 micrograms of preformed vitamin A may be toxic for adults, according to the Linus Pauling Institute at Oregon State University. A dose of more than 600 mcg may be toxic for infants and young children. Hypervitaminosis A, or vitamin A toxicity, can produce symptoms such as fatigue, headaches and nausea. It may also contribute to liver damage, and may result in a coma.
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