Vitamin K: No Help for Bone Density
But Study Shows Vitamin K May Offer Some Protection Against Fractures and Cancers
Oct. 14, 2008 -- Though often touted as a way to strengthen bones, taking
vitamin K for osteopenia does not protect
postmenopausal women from age-related declines in bone density, a new study
But it may help them avoid fractures or cancers.
The findings relating to fracture and cancer avoidance were
"unexpected," says Angela Cheung, MD, of Toronto's University Health
Network and lead author of the study. "It is intriguing and gives us reason
for additional research."
The study, published in the journal PLoS Medicine, involved 440
postmenopausal women diagnosed with osteopenia, a "warning" condition
of bone loss that can be a precursor to osteoporosis. The disease causes bones
to become more fragile and likely to break.
Cheung says the women were either given a vitamin K supplement or a placebo
for two years, with 261 continuing for two more years.
"Bone density scans after two years and after four years revealed there
were no differences in bone density between the two groups, and that bone
density had decreased by similar amounts," Cheung says. "But fewer
women over the four-year period had fractures, and fewer had cancer."
Vitamin K and Osteoporosis
Low-dose vitamin K for osteoporosis has been "promoted by the lay media
for increasing bone mass" and is widely available in health food stores and
over the Internet, according to study researchers.
In Japan, Cheung tells WebMD, vitamin K is an approved treatment for
But the study researchers say the value of vitamin K to lower risk of bone
loss or fractures "remains controversial." The study, whose
participants were chosen because they had been diagnosed with osteopenia,
concludes that 5 milligrams of vitamin K supplementation daily did not protect
them against age-related declines in bone mineral density "at the lumbar
spine, total hip, femoral neck, or ultradistal radius" even if they had
plenty of vitamin D.
Roberto Pacifici, MD, director of the division of endocrinology at Emory
University in Atlanta, says he was unimpressed with the study because it's
"been known for some time that there really is no connection between
osteoporosis and vitamin K. If you have enough vitamin K deficiency to cause
bone weakness, you bleed to death."
He says vitamin D is "very important" for bone strength, but that
"people should not go out and buy vitamin K because of this study."
Although Cheung says it would be premature to recommend vitamin K for
osteoporosis, she believes it deserves further study in larger groups of
About 10 million Americans, 80% of them women, have been diagnosed with
osteoporosis; another 34 million people in the U.S. are at risk, according to
the National Osteoporosis Foundation.
Previous research suggesting vitamin K supplements might strengthen
bones may have had "design and methodological" flaws, Cheung says.
Women in the study did develop fewer fractures, a finding that Cheung says
she could not explain and needed further research. Over the four years, nine
women had fractures among those taking vitamin K supplements, vs. 20 in the