As usual, the headline ought to be taken from the publication. Bone strength was virtually unchanged for every group in the study; no participant had osteoporosis. Mean BMD went down a hair for all groups, but estimated failure load was considered statistically the same:
> At trial end[...]
> mean percent change in [radial] volumetric BMD of −1.2% (400 IU group), −2.4% (4000 IU group), and −3.5% (10 000 IU group).
> mean percent change [...in tibial volumetric BMD] of −0.4% (400 IU), −1.0% (4000 IU), and −1.7% (10 000 IU).
> There were no significant differences for changes in failure load (radius, P = .06; tibia, P = .12).
Agreed the differences look small but find a copy of the full article (I would link but I saw a hard copy). The time curve will convince you this effect is real. All participants start at the same place and you see the dose curves move apart over time and very consistently. What definitely isn’t clear is whether vitamin D supplementation is benefiting the participants at all, thanks to their lack of a proper control.
The bone density decreases may look minor on paper but look at it this way: it’s quite possible that a very large cohort of elderly and middle aged people concerned about their bone health (potentially because they were told they have reason to be concerned) have been paying a lot of money annually to actually worsen their situation. That sucks.
> At trial end[...]
> mean percent change in [radial] volumetric BMD of −1.2% (400 IU group), −2.4% (4000 IU group), and −3.5% (10 000 IU group).
> mean percent change [...in tibial volumetric BMD] of −0.4% (400 IU), −1.0% (4000 IU), and −1.7% (10 000 IU).
> There were no significant differences for changes in failure load (radius, P = .06; tibia, P = .12).