Vitamin A is essential to human life, but too much of it can cause serious adverse effects. Consuming too much of this nutrient can lead to vitamin A toxicity, a condition referred to as hypervitaminosis A. By educating yourself about the types of vitamin A and the recommended dietary allowances established by the Institute of Medicine, you can avoid vitamin A toxicity.
Types of Vitamin A
Vitamin A describes a large number of nutritional compounds. Preformed vitamin A is a term used in reference to two types of vitamin A called retinol and retinal. These two compounds are also referred to as retinoids. Provitamin A carotenoids are a type of nutrient that your body can convert into retinol. According to the Office of Dietary Supplements, provitamin A carotenoids are generally recognized as safe and, unlike retinoids, high dosages of provitamin A carotenoids are not associated with adverse health effects.
Acute vs. Chronic Hypervitaminosis A
Hypervitaminosis A, or vitamin A toxicity, results when you consume excessive dosages of preformed vitamin A. Your body absorbs this type of vitamin A rapidly and excretes it slowly. As a result, vitamin A can accumulate in your body to reach toxic levels. Hypervitaminosis A can occur rapidly if you are taking high dosages, or more gradually if the dosage is lower but still exceeds your needs.
Effects of Vitamin A Toxicity
Acute hypervitaminosis A, though rare, can cause nausea, dizziness, dry flaky skin, and swelling in your brain. Chronic hypervitaminosis A also causes these symptoms, in addition to bone and joint pain. Vitamin A toxicity can cause birth defects and increase your risk of osteoporosis, according to the Linus Pauling Institute.
Dosages
Your need for vitamin A depends upon your age and gender. For most adult males, the recommended dietary allowance for preformed vitamin A is 900 micrograms per day. For adult females who aren't pregnant or lactating, the RDA for preformed vitamin A is 700 micrograms per day. Tolerable upper level of intake, or UL, is the highest daily dosage of a nutrient that is likely not to cause adverse health effects. The UL for preformed vitamin A for adults 19 and older is 3,000 micrograms per day.
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