Hip fractures among postmenopausal women and Vitamin A intake.





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Vitamin A, also know as retinol, wasn't even known about until 1913, when scientists discovered it could prevent night blindness. Then, in 1932 it was discovered that beta-carotene, also known as pro-vitamin A, was the precursor to vitamin A. When we consume beta-carotene, vitamin A is produced naturally by enzymes in the digestive tract that break beta-carotene down. The fat-soluble vitamin A is then stored in the liver, where it can remain for long periods of time.

The use of vitamin A supplements supports vision and prevents drying of the cornea. It also plays an important role in maintaining the integrity of epithelial tissues, which consist of the mucous membrane-secreting cells that line all the glands and organs of the body. Many studies report that adequate intake of vitamin A is associated with reduced risk of various epithelial-cell cancers. It is essential for the growth of bones, teeth, and soft tissues.

Vitamin A toxicity can include symptoms such as dry itchy skin, brittle nails, hair loss, bone pain, headaches, muscle and joint pains, increased infections, enlarged liver, and abnormal liver function. In animal studies toxic levels of vitamin A can have adverse skeletal effects. A recent study investigated the correlation between high amounts of vitamin A and postmenopausal hip fractures in women. Beginning in 1980, 72,337 women involved in this study were followed for 18 years. In association with the Nurses' Health Study, these postmenopausal women were aged 34 to 77 years. The number of fractures, along with intake of vitamin A and multivitamins, was recorded at baseline and during the study. During the extent of the study, 603 hip fractures occurred. Women with the highest intake of vitamin A had a substantially increased relative risk of hip fracture compared with women with a low intake. The increase was chiefly due to retinol, although the risk was lessened if women were using postmenopausal hormones. Retinol obtained through food was also associated with fracture risk. In conclusion, the authors stated that long-term intake of vitamin A may increase the risk of postmenopausal hip fractures, and that the levels of retinol in supplements and foods may need to be re-examined.1


1. Feskanich D. Vitamin A Intake and Hip Fractures Among Postmenopausal Women. JAMA. Jan 2002;287:47-54,102-103.