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Q: The research study you wrote about found that excessive levels of vitamin A increased the risk of bone fractures but that beta-carotene was not associated with this same risk. You said this was presumably because the body converts beta-carotene to vitamin A only as needed. Couldn't you just take beta-carotene instead of vitamin A?
A: Yes and no.
Yes: If you get your beta-carotene primarily from diet (veggies and fruits such as sweet potatoes, carrots, spinach, mango, and cantaloupe), which provides ample amounts.
Probably no: If you mean high-dose beta-carotene in supplement form, particularly if you smoke or consume alcohol excessively. Supplement pills in doses of 20 mg daily are associated with a higher risk of heart disease and cancer in people who smoke. It's not known whether this risk might apply generally, so it's best to be wary of supplemental beta-carotene in amounts significantly higher than standard multivitamin products provide.
Q: In regard to your recent column on Vitamin A and bone fractures, my multivitamin says it contains 5,000 IU of vitamin A. Is this too much, given that I also eat a lot of dairy products?
A: I'm assuming that the 5,000 IU is "straight" vitamin A , that is, no beta-carotene. This is quite a bit more than the RDAs (2,300 IU for women and 3,000 IU for men), but only half the safe upper level currently set at 10,000 IU.
However, the important consideration is the possible bone-weakening effect and increased risk for osteoporosis associated with excessive levels of vitamin A.
You're also getting vitamin A from diet and vitamin A-fortified foods. You might wish to choose a multivitamin product that conforms more closely to the RDAs for vitamin A.
Vitamin RDAs don't have to be ingested every day. The body can store limited amounts of some nutrients for use on days when supplies might fall short. Ideally, over a period of several days or weeks, daily amounts should average out to the RDA.
(Richard Harkness is a consultant pharmacist who writes on health care topics. You can write him at 1224 King Henry Drive, Ocean Springs, MS 39564. His e-mail address is firstname.lastname@example.org. Volume of mail prohibits individual replies; selected letters will be answered in his column.)
(c) 2003, The Sun Herald (Biloxi, Miss.). Distributed by Knight Ridder/Tribune News Service.