On Nutrition: Confusion about Vitamin A and Calcium
By Barbara Quinn
http://www.JewishWorldReview.com | Christine P. writes:
"Dear Barbara Quinn,
My question concerns A-vitamin. I am taking a multivitamin for women over 50 that contains a large amount of vitamin A beta carotene. I am concerned that this might be too much. I am 70 years old and in excellent health.
I also take a calcium supplement plus vitamin D and other medications to lower my cholesterol and blood pressure. I am considering to drop the calcium supplement, I heard a new study does question the absorption of calcium into the bones. I would like to have your opinion on the vitamin A and calcium."
Dear Christine, my opinion is this: As much as we try to simplify nutrition recommendations, they are really quite complex. Hence the following:
Vitamin A is actually a group of related compounds that are essential for good vision, immune function and reproduction. In food, vitamin A is in two major forms: "Pre-formed" (retinol or retinal ester) is found in fish oils, liver, and dairy foods. "Pro-vitamin A" (alpha- and beta-carotene) is found in orange, yellow and leafy green vegetables, tomatoes and fruit) and is converted to active vitamin A in the body.
Dietary supplements may contain both forms of vitamin A and the label should tell you that. This is important because excess "preformed" vitamin A (retinol) can be toxic and has also been associated with an increase in bone fractures. On the other hand, beta carotene is rarely toxic except in the case of smokers or asbestos workers who take it in high doses.
What is confusing is that nutrition labels often list vitamin A in IU's (international units) while nutrition experts consider RAE's (retinol activity equivalents). And RAE's are different based on the source of the nutrient. (Confusing, yes?)
In general, if your dietary supplement contains more than 10,000 IU's of "preformed" vitamin A (often listed as retinol or palmitate), that's too much. Many supplement labels will also list what portion of the vitamin A content is in the safer form of beta carotene.
Regarding calcium, you may be referring to the recent draft (not set in stone) document by the US Preventive Services Task Force (USPSTF) that specifically addresses the use of calcium and vitamin D supplements to prevent bone fractures from osteoporosis in woman past the age of menopause.
This task force concludes "with moderate certainty" that a daily supplement less than 400 IU of vitamin D-3 and 1000 mg of calcium carbonate does not appear to prevent a first-time fracture from osteoporosis in older women. And there is not enough evidence to support taking more than these amounts either.
However … this draft report says there is good evidence that vitamin D supplements can help prevent falls (that can lead to fractures) in people over the age of 65.
Adequately confused? It's a good reminder to look closely at who and what is being studied. Better yet, get the advice of a nutrition professional who can personalize your dietary needs according to your unique health and medical concerns.
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Barbara Quinn is a registered dietitian and certified diabetes educator at the Community Hospital of the Monterey Peninsula.
© 2011, The Monterey County Herald Distributed by McClatchy-Tribune Information Services