There are 13 different vitamins essential to your good health. They help you grow, aid in nerve and digestive functions and bolster your immune system. If you eat a variety of foods, you'll get most of the vitamins you need. The Institute of Medicine, or IOM, has set minimum requirements, called daily reference intakes, or DRI, for the amount of each vitamin you should consume daily. In some cases, the IOM has also set upper limits for these nutrients, as an excess of some, such as vitamin A, can cause toxicity or poisoning.
Hypervitaminosis
Hypervitaminosis is another word for vitamin toxicity or vitamin poisoning. It can occur as an acute attack, similar to an overdose of other types of pills or medicines, or it can occur chronically, meaning it happens if you take excessive doses of vitamins over a period of time. Vitamins can be water soluble or fat soluble, but most hypervitaminosis occurs with fat-soluble vitamins. This is because the water-soluble vitamins, such as vitamin C and the B vitamins, are readily absorbed into the body and any excess is eliminated in your urine. Fat-soluble vitamins, such as vitamin A, D and E, are stored in the body, making toxicity more of a possibility, though it is still unusual.
Vitamin A Toxicity
Vitamin A can be found in a number of forms, divided between carotenoids that come from plants, and retinoids that originate in animal-based foods. The recommended dietary allowance for vitamin A is 900 mcg for adult men and 700 mcg for adult women each day, according to the Office of Dietary Supplements, or ODS. ODS has set a tolerable upper intake level for the retinol form of vitamin A at 3,000 mcg for adults of either gender, beyond which you should be concerned about vitamin A toxicity. An upper limit has not been set for the beta-carotene or other carotenoid forms of vitamin A, but research is ongoing.
Symptoms
Hair loss and brittle nails are symptoms of chronic vitamin A toxicity, the more common form, which could occur if you regularly consume large doses of vitamin A. Synthetic retinoids, such as those used to treat acne and other skin conditions, are also a potential source of such toxicity. Other symptoms include hydrocephalus, vomiting, fatigue, constipation, bone pain and severe headaches. If the toxicity is from beta-carotene, your skin may take on a yellowish tint. The Encyclopedia of Nursing and Allied Health says that 20 mg or more of retinol taken on a regular basis can lead to birth defects, so pregnant women need to be especially vigilant about the amount of vitamin A they get in their diet.
Treatment and Prevention
Hypervitaminosis A symptoms usually subside if you simply take a smaller dosage or eliminate supplemental vitamin A, except as a component of your daily multivitamin. If you eat a well-balanced diet with plenty of colorful vegetables, as well as some dairy or meat each day, you should meet the DRI for vitamin A.
References
- USDA: Dietary Guidance
- Office of Dietary Supplements: Vitamin A
- Patient.co.uk; Hypervitaminosis; Richard Draper, M.D.; Feb. 2011
- "The Gale Encyclopedia of Nursing & Allied Health"; Vitamin Toxicity; Lisa Maria Andres, et al; 2002
- "Medline Plus"; Hypervitaminosis A; David C. Dugdale, May 2010
- "Linus Pauling Institute"; Vitamin A; Jane Higdon, et al; Nov. 2007
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