Study: Vitamin Linked to Fractures

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Wednesday January 2 9:04 AM ET

Study: Vitamin Linked to Fractures

By TAMMY WEBBER, Associated Press Writer

CHICAGO (AP) - Too much vitamin A may increase the risk of hip fractures in

older women, according to a new study that researchers say suggests the need to

reevaluate the levels in supplements and fortified food.

Vitamin A is important for such things as healthy skin and hair and bone growth.

But in the study published in Wednesday's Journal of the American Medical

Association (news - web sites), researchers found that women with the highest

total intake - both from food and vitamin supplements - had double the risk of

hip fractures compared with women with the lowest intake.

One theory is that too much vitamin A inhibits the ability of Vitamin D to help

the body absorb calcium, said lead author, Diane Feskanich, an epidemiologist at

Brigham and Women's Hospital in Boston. She said previous studies also suggest

vitamin A affects cells that work in bone remodeling - the breakdown and

rebuilding of bone.

``There is a biologic reason to support what we're observing, but we don't know

what those reasons are,'' said Feskanich, adding that the research confirms the

findings of an earlier Swedish study.

The adverse effects appear to be caused only by too much retinol - the true form

of vitamin A, found in such things as liver, fish oils and supplements - and not

by foods rich in beta carotene, such as dark, leafy vegetables. Beta carotene is

converted by the body to vitamin A as needed.

Researchers analyzed dietary questionnaires from more than 70,000 postmenopausal

woman - all nurses from 34 to 77 years old. From 1980 to 1998, there were 603

hip fractures from such things as falling from the height of a chair or

tripping.

The risk was almost twice as high among women with retinol intake of about 2,000

micrograms or more per day, compared with those with intakes of less than 500

micrograms daily. And women specifically taking a vitamin A supplement had a 40

percent greater risk of hip fracture than women not taking the supplement,

Feskanich said.

The Institute of Medicine (news - web sites) - a private science organization

that sets the nation's recommended daily allowances for nutrients - recommends

that women get 700 micrograms a day of the vitamin. But multivitamins typically

contain about 1,500 micrograms because the U.S. Food and Drug Administration

(news - web sites) has not updated vitamin supplement labels, Feskanich said.

She said that between multivitamin supplements and fortified food, it is not

difficult for women to attain vitamin A levels high enough to cause problems.

Some increased risk was even seen at the old recommended levels.

``If you're taking a multivitamin and consuming fortified milk and cereal ...

after a while, there are just too many sources,'' she said.

She said the FDA should consider lowering labeling standards for vitamin A.

Also, some foods currently fortified with the vitamin might not need to be, or

could be fortified with beta carotene instead of retinol, she said.

Researchers cautioned that people should not stop taking multivitamins, which

help lower the risk of other diseases. Instead, consumers might consider a

multivitamin that supplies some of its vitamin A from beta carotene, said

co-author, Dr. Walter Willett, professor of epidemiology and nutrition at the

Harvard School of Public Health.

The Council for Responsible Nutrition, a trade group for the dietary supplement

industry, played down the significance of the study, saying another recent

survey found no connection between high vitamin A intake and bone density

problems. The study of nurses was ``observational'' only, the trade group said,

and ``by its very nature, never provides proof'' but only suggests further

study.

But Dr. , a nutrition professor at the University of North Carolina

at Chapel Hill, said the study appears to show a strong link between high

vitamin A levels and hip fractures.

But, ``I think we kind of need to wait and see,'' said , who was not

involved in the study. ``There is enough suggested evidence from previous

studies and this one that it's very possible we're overfortifying and

oversupplementing in the U.S. But it's unclear what a safe upper limit is, and

the issue needs to be resolved more with clinical studies.''

In an accompanying editorial, Dr. Margo A. Denke of the Center for Human

Nutrition at the University of Texas Southwestern Medical Center said the

findings support the need to set a safe upper limit to dietary retinol only.

She noted that the study participants were white U.S. women of high

socioeconomic status, and said further study is needed on populations with diets

less rich in vitamin A, ``to avoid confronting the other, even more hazardous

side of the sword - vitamin A deficiency.''

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