Too Much Vitamin A Can Lead to Weak Bones and Fractures
Vitamin A is essential for proper vision, allowing new cells to form, and supporting reproduction and growth (including immune system strength). Sounds wonderful, you may be thinking, and decide to consume large amounts of vitamin A. There's a problem with this strategy though - vitamin A is fat soluble, accumulating in your liver and fat cells when you eat more than you currently need. At high levels, this stored vitamin A exceeds your body's tolerable level, and starts causing significant harm.
You ingest vitamin A in two main forms:
- Preformed vitamin A, which is this vitamin in a form that it can be directly used by your body. You get preformed vitamin A from animal foods (especially liver, fish liver oils, dairy products, and eggs). Some "fortified" foods, multivitamins, and some other supplements also may contain preformed vitamin A.
- Carotenoids, pigments in many plant foods, that your body converts to vitamin A through a regulated process. The carotenoid that your body most easily changes to vitamin A is beta-carotene.
Nutritionists have developed a couple rather complex ways of determining how much vitamin A you need, whether from preformed sources or carotenoids. Rather than wading through all the complexities, it's easiest to just think in term of IUs (International Units), which are commonly used. The recommended dietary allowance (RDA) for vitamin A daily is 3,000 IU for men, 2300 IU for women, with other amounts for infants and children. The daily upper level of intake, which should not be exceeded, is 10,000 IUs.
Vitamin A Toxicity
Vitamin A toxicity comes from eating too much preformed vitamin A from animal foods, fortified foods, and/or supplements. This can happen quickly from a single large dose, which results in acute vitamin A toxicity. Symptoms of this condition include nausea, headache, fatigue, loss of appetite, dizziness, dry skin, and brain swelling.
Much more common, however, is chronic vitamin A toxicity from consuming a bit too much preformed vitamin A over a longer period of time. You do not need to eat more than the upper level of intake for this to happen - you only have to eat more preformed vitamin A than you need. The threshold to develop this condition varies among different individuals. Remember, this vitamin accumulates in the liver and other fatty tissues, and your body has no good way to get rid of it. This is especially dangerous in pregnant women, as too much vitamin A in the mother's body during pregnancy can lead to serious birth defects in the baby.