Low vitamin B tied to hip fracture risk

NEW YORK (Reuters Health) - Older adults who are low in B vitamins or have elevated levels of a blood protein called homocysteine may be at increased risk of suffering a hip fracture, new study findings suggest.

The body's homocysteine levels are known to go up when B vitamin levels are depleted. However, in the new study, researchers found that homocysteine and certain B vitamins were each independently linked to hip fracture risk.

Among more than 1,000 elderly men and women, those who were deficient in vitamin B12 were 60 percent more likely than those with normal levels to sustain a hip fracture over four years. A similar risk was seen among those deficient in vitamin B6.

When the researchers looked at homocysteine levels, they found that men and women with high levels were 50 percent to 70 percent more likely to suffer a hip fracture -- even when their B vitamin levels were taken into account.

"We've seen evidence in the past that high homocysteine is associated with elevated risk of hip fractures," lead investigator Dr. Robert R. McLean said in an interview. However, he added, it has been "hard to disentangle whether low vitamin B status is a causal mechanism or whether high homocysteine is a causal mechanism."

He and his colleagues report these latest findings in the Journal of Clinical Endocrinology and Metabolism.

Lab research suggests that B vitamins play a role in maintaining bone density, and studies have linked low blood levels of the vitamins with low bone mass.

Consistent with this, McLean and his colleagues found that as study participants' B6 levels declined, their bone loss accelerated, on average.

In contrast, although homocysteine was related to hip fracture risk, it was not related to bone loss. For now, it's not clear why the protein is linked to hip fractures, the researchers say.

Diet changes and vitamin supplements are "easy and effective methods" for controlling B vitamin and homocysteine levels, McLean and his colleagues note. The current findings, they say, suggest that such measures should be studied as "potential novel measures" for preventing bone fractures.

However, McLean said, "I think that it's still too early to tell people to start taking their B vitamins to prevent fractures. We need clinical trial evidence to give us a better picture of what's really going on."

Vitamin B6 is found in foods like potatoes, bananas, beans and fortified cereals; vitamin B12 is found mainly in meat, fish and poultry.

SOURCE: Journal of Clinical Endocrinology and Metabolism, June 2008.