May 15, 2019
By Lisa Rapaport
(Reuters Health) - Older women who take supplements with high doses of vitamins B6 and B12 may be more likely than their counterparts who don't to experience hip fractures, a U.S. study suggests.
While some previous research has linked both of these vitamins to a lower risk of heart disease, results have been mixed and some studies have also tied B6 and B12 to fractures in older adults, researchers note in JAMA Network Open, May 10.
Under current U.S. dietary guidelines, women over age 50 should get 1.5 mg a day of B6, and girls and women aged 14 and older should get 2.4 mcg daily.
For the current study, researchers followed almost 76,000 female nurses in the U.S. for an average of 21 years, doing extensive dietary surveys roughly every four years. Almost all of the women in the study had total intake of B6 and B12 from foods and supplements that was higher than recommended.
About 2,300 women had hip fractures during the study, and half of them had these fractures before they were 76 years old.
Compared to women who had the lowest intake of both vitamins, women who had the highest daily intake - at least 35 mg of B6 and 20 mcg of B12 - were 47 percent more likely to have hip fractures during the study.
"Many people take supplements without clear indications, and high dose vitamin supplements are readily available in drug stores and on the internet," said lead study author Dr. Haakon Meyer of the University of Oslo in Norway.
"Our results add to other reports suggesting that high-dose vitamin supplementation can lead to unexpected adverse effects," Meyer said by email. "Normal intakes of these vitamins, corresponding to recommended dietary allowances, were not associated with increased fracture risk."
Vitamin B6 helps the body maintain a healthy metabolism and immune system and is found in a variety of foods, including meat, fish, chickpeas, potatoes and other starchy vegetables. B12 helps the body make red blood cells and is naturally found in clams, fish, meat, eggs and dairy products.
The study wasn't designed to prove whether or how high intake of B6 or B12 might contribute to risk for hip fractures.
It's also possible that the study population of predominately white, insured and middle class women might not reflect what would happen with all older women in the U.S.
Even so, the results underscore the importance of getting a checkup before starting any vitamin supplements, said Dr. Karen Hansen, a researcher at the University of Wisconsin School of Medicine & Public Health in Madison.
"Women should seek their primary care provider's advice on whether to take a vitamin B supplement," Hansen, who wasn't involved in the study, said by email.
"If the provider documents a vitamin deficiency, then a supplement is clearly warranted," Hansen said. "However, in the absence of a documented deficiency, (several) studies collectively suggest that vitamin B6 and vitamin B12 will not improve skeletal health, and might even be harmful."
JAMA Netw Open 2019.
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