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Wednesday, 2 January, 2002, 16:19 GMT
Vitamin A link to hip fractures
X-ray scan
Vitamin A may interfere with absorption of calcium
Too much vitamin A in the diet may increase the risk of hip fractures in older women, according to research.

Women eating at least 3,000 micrograms of vitamin A each day were at 48% higher risk of suffering a hip fracture than those who consumed less than 1,250 micrograms of the vitamin daily, the survey found.

The adverse effects appear to be caused only by too much retinol - the true form of vitamin A, found in such products as liver, fish oils and supplements.

They do not seem to be caused by foods rich in beta carotene, such as dark, leafy vegetables, according to the report in the Journal of the American Medical Association.


The amounts of retinol in fortified foods and vitamin supplements may need to be reassessed

Diane Feskanich, epidemiologist
Beta carotene is converted by the body to vitamin A as required.

Women specifically taking a vitamin A supplement had a 40% greater risk of hip fracture than women not taking the supplement.

Researchers analysed dietary questionnaires from more than 70,000 postmenopausal women - all nurses from 34 to 77 years old - over an 18-year period.

They found 603 women had hip fractures after only mild or moderate trauma.

Re-assessment

One theory is that too much vitamin A inhibits the ability of vitamin D to help the body absorb calcium, said the report's lead author epidemiologist Dr Diane Feskanich.

She said previous studies suggest vitamin A affects cells that work in bone remodelling - the breakdown and building of bone.

She said: "There is a biologic reason to support what we're observing, but we don't know what those reasons are.

"The amounts of retinol in fortified foods and vitamin supplements may need to be reassessed since these add significantly to total retinol consumption.

"If you're taking a multivitamin and consuming fortified milk and cereal... after a while, there are just too many sources."

An adult needs about 600-700 micrograms of vitamin A daily to maintain healthy skin, hair and immune system.

Multivitamin tablets typically contain about 1,500 micrograms.

'Speculative' research

A National Osteoporosis Society spokesman said: "It is important to note that the study is an observational one and thus can only be used to speculate concerning dietary/bone health associations and encourage further research in the area.

"Interestingly, there is a high incidence of osteoporosis in both men and women from Scandinavian countries, where sunlight exposure is limited and intake of vitamin A is particularly high.

"Previous work has shown a link between high dietary intake of vitamin A and the development of osteoporosis.

"Furthermore, vitamin A is known to antagonise the action of vitamin D."

Researchers cautioned that people should not stop taking multivitamins, which help lower the risk of other diseases.

See also:

15 Dec 01 | Health
Osteoporosis cases 'being missed'
20 Oct 01 | Health
'I felt my spine fracture'
04 Jun 01 | Health
Osteoporosis 'runs in families'
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