A study just published in JAMA Internal Medicine examined the effects of placebo, low-dose cholecalciferol (Vitamin D3), and high-dose cholecalciferol on 1-year changes in total fractional calcium absorption, bone mineral density, Timed Up and Go and five sit-to-stand tests, and muscle mass in postmenopausal women with vitamin D insufficiency. This study was undertaken because “expert” advice had suggested that patients (especially postmenopausal women) with vitamin D levels below 30 ng/L were at increased risk for a variety of health problem, especially decreased bone mass. These conclusions were to a large degree inferential and not based on controlled prospective studies.
Doctors in practice took to measuring vitamin D levels and to treating those patients whose levels were below the above mentioned 30 ng/L. All of this medical busy work was based on good intentions and the best analysis that could made on the basis of available evidence. This sort of thing happens all the time. The urge to treat seems hard wired into the brains of all who would treat the sick or the maybe sick.
The current study was a randomized, double-blind, placebo-controlled clinical trial. It concluded that “[h]igh-dose cholecalciferol therapy increased calcium absorption, but the effect was small and did not translate into beneficial effects on bone mineral density, muscle function, muscle mass, or falls. We [the study’s authors] found no data to support experts’ recommendations to maintain serum 25(OH)D levels of 30 ng/mL or higher in postmenopausal women. Instead, we found that low- and high-dose cholecalciferol were equivalent to placebo in their effects on bone and muscle outcomes in this cohort of postmenopausal women with 25(OH)D levels less than 30 ng/mL.”
In other words treating older women with vitamin D accomplished nothing. Not a big surprise. Whether similar results will be found in other populations with other health problems is uncertain. But the burden of proof about the use of extra vitamin D should be on those who advocate its use. In medicine less is more, more often than not.