Vitamin D supplements may not stop bones from deteriorating with age but calcium might.
Researchers at Winthrop University Hospital studied more than 100 women who were either given high doses of vitamin D, a normal dose of calcium, a combination of both supplements, or no supplements at all.
They found those taking calcium alone experienced a drop in bone turnover -- which is what happens when the body breaks down old bone.
However, vitamin D did not have any effect on bone turnover.
If the body breaks down bone faster than it can replace it, osteoporosis develops.
Researchers say it appears vitamin D helps bones absorb calcium, but it does not improve bone health on its own.