Elevated homocysteine is a strong risk factor for osteoporotic fractures in the elderly, and may not simply be a marker of lack of vitamin B, researchers report in the June issue of the Journal of Clinical Endocrinology and Metabolism.
"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, "it's hard to disentangle whether low vitamin B status is a causal mechanism or whether high homocysteine is a causal mechanism."
To investigate further, Dr. McLean, of the Institute for Aging Research, Boston and colleagues examined information on more than 1000 men and women taking part in the Framingham Osteoporosis Study. The researchers used data at baseline in 1987 to 1989 and at four-year follow-up to calculate the annual percent change in bone mineral density (BMD).
Adjusted mean bone loss was inversely associated with vitamin B6, the investigators found.
Through 2003, there were a total of 111 hip fractures, and levels of vitamin B6 and B12 showed a significant inverse association with hip fracture risk.
Nevertheless, these associations were attenuated and lost significance after controlling for baseline BMD, serum vitamin D, and homocysteine.
After adjusting for folate and vitamin B6, subjects with homocysteine levels of 14 micromol/L or more had about a 70 per cent higher fracture risk. However, this was attenuated after controlling for vitamin B12.
Thus, say the investigators, "Low B-vitamin concentration may be a risk factor for decreased bone health, yet does not fully explain the relation between elevated homocysteine and hip fracture."
Dr. McLean added, "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."
