Vitamin A and hip fracture risk
The evidence is piling up that too much vitamin A weakens bones and
leads to hip fractures. In 2002, Harvard Medical School researchers
reported that high vitamin A intake raises the risk for hip fracture
in postmenopausal women. The data suggest that the main culprit is retinol,
the active form of the vitamin. Retinol is found in supplements, liver,
eggs, full-fat dairy products, fish liver oils, and fortified foods
such as cereals and skim milk.
Since then, other studies have linked excess retinol to decreased bone
strength and greater fracture risk — especially at the hip. The
consistency of this evidence suggests that older men and women should
consider limiting their retinol-derived vitamin A, particularly from
A long-term Swedish study found that men with high blood levels of retinol
had a risk for hip fracture double that of subjects with average levels.
Beta-carotene levels were not associated with increased risk. Also, people
whose daily vitamin A consumption was more than 5,000 IU (International
Units) per day had a hip fracture risk about double that of participants
whose intake was less than 1,666 IU per day.
The study also has meaning for women because they have less bone at
midlife and more hip fractures at earlier ages than men do. They also
take more supplemental vitamins, the likeliest source of excess vitamin
Vitamin A is important for vision, the immune system, and healthy tissues.
Although vitamin A deficiency is a leading cause of blindness in developing
countries, it’s not a major problem in the United States. In this
country, health experts worry more about high levels, especially for
older people who may have difficulty metabolizing retinol properly.
We know from studies using animals and human cells that excess retinol
stimulates cells that break down bone (osteoclasts) and interferes
with cells that build new bone (osteoblasts).
Unless you have a health condition involving vitamin A and are under
a clinician’s care, you may want to take the following precautions:
- Don’t take vitamin A supplements.
- When shopping for a multivitamin, look for one that derives part
or all of its vitamin A from beta-carotene. If the amounts of retinol
and beta-carotene aren’t listed on the label, call the manufacturer
(many labels display a toll-free number).
- Be aware that the “% Daily Value” of vitamin A listed
on food and supplement labels is based on a daily intake of 1,500 mcg
(micrograms; 5,000 IU) per day for adults. A scientific panel recently
updated the recommended amount, lowering it to 700 mcg (2,330 IU) per
day for women. Until we know more, don’t exceed 1,500 mcg of
retinol from both food and multivitamins.
- Eat lots of colorful vegetables (carrots, spinach, red pepper, tomatoes)
and orange fruits (oranges, apricots, peaches). They provide vitamin
A from beta-carotene, plus other important nutrients. You can’t
get too much beta-carotene because it converts to vitamin A only as
the body needs it.
New England Journal of Medicine, Jan. 23, 2003
March 2003 update
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