Dr. Charles Ginsberg of Veterans Affairs San Diego Healthcare System, who helped to conduct the study on VMR and 25(OH)D. The VMR and 25(OH)D does not consistently associate with essential bone outcomes like hip fractures. However, a parameter that is currently used to assess VMR and 25(OH)D was a defective measure. The findings were published online in Bone.

A new study suggests that VMR ratio predicts fracture risk better than 25(OH)D. VMR might be a better marker of bone health than 25(OH)D. Dr. Ginsberg and his colleagues looked at data from the Cardiovascular Health Study on 890 community-dwelling elders, who had a mean 25(OH)D of 28 ng/mL. They also measured the VMR or the ratio of the catabolic product 24,25(OH)2D to 25(OH)D.

A 1% increase in VMR, 25(OH)D, or 24,25(OH)2D was linked with 0.26%, 0.32%, 0.25% lower parathyroid hormone (PTH) levels, respectively (P<0.05 for all). Bone mineral density (BMD) data were available for 358 study participants. There was no association between 25(OH)D or VMR and BMD, but there was a modest association between increased 24,25(OH)2D and higher hip BMD.

During follow-up of 8.4 years, 289 hip fractures occurred. Risk of hip fracture fell significantly with increased 24,25(OH)2D and VMR (hazard ratio per standard deviation, 0.73 and 0.74, respectively). However, there was no significant association between 25(OH)D and hip fracture risk.

Dr. Ginsberg noted, A person in the highest quartile of VMR would have half the risk of hip fracture compared to someone in the bottom quartile.

While Americans spend billions of dollars on vitamin D supplements, he added, basing the need for supplementation on 25(OH)D levels may not identify people who would truly benefit. "That's not necessarily the number we should be following; perhaps we should be following the VMR," he said.

According to Dr. Ginsberg, further studies would show if increasing an individual's VMR reduces their fracture risk. VMR could also use to look at levels of vitamin D about the risk of multiple sclerosis and several other illnesses, he added.