Overcoming the vitamin D hype

The United States Preventive Services Task Force has released a draft recommendation that 400 IU of vitamin D and 1,000 mg of calcium has not been shown to prevent fractures in postmenopausal women.

I try and keep up with the literature, and I cannot recall any data that suggest otherwise.

There is no doubt that vitamin D deficiency has an adverse effect on skeletal health, but the skeletal disease resulting from vitamin D deficiency is osteomalacia, not osteoporosis. In osteomalacia, the abnormality is not a decrease in bone mass but a decrease in the proportion of bone that is fully mineralized. This leads to pseudo-fractures or “looser” zones and bone pain. This is often accompanied by muscle weakness. The serum calcium may be low or at the lower end of the reference interval, and parathyroid hormone (PTH) is generally elevated. An important lab abnormality is an elevated alkaline phosphatase — in severe cases several times higher than the upper limit of the reference interval.

One item often missing from the massive literature on vitamin D (10,098 articles in PubMed in the last five years, 2,329 of which were reviews) is the ethnic difference in vitamin D levels that is not associated with skeletal disease.

Almost two decades ago our group reported the following in the Journal of Bone and Mineral Research:

“[Bone mineral density] measured by DXA was greater in the forearm (9.8%), spine (8.7%), and femoral neck (14.7%) in black women (P < .001 at all sites). At L1 measured by QCT, adjusted BMC in the black women was 37.4% greater than in the white women (P< .001). Serum calcidiol was significantly lower and serum PTH and calcitriol significantly higher in the black women. Despite this, biochemical markers of bone resorption and formation were significantly lower in the black women. We conclude that skeletally healthy older black women have a greater bone mass and lower rates of bone remodeling than a comparable group of white women.”

I am in complete agreement that 400 IU of vitamin D and 1,000 mg of calcium daily has not been shown to prevent fractures in postmenopausal women. Additionally, 25-hydroxyvitamin D assays are measured all too often, and the expense is not justified given the low cost of over-the-counter vitamin D.

Despite all of the articles attempting to relate vitamin D deficiency to a wide range of health issues, to my knowledge the only diseases clearly documented to be the result of vitamin D deficiency are rickets (children) and osteomalacia (adults).

Since the vitamin D receptor is ubiquitous, I will not be surprised that over time someone will provide clear-cut evidence that low levels of vitamin D will result in a systemic disease that can be controlled or prevented to a great extent by ensuring that vitamin D intake is adequate. Until then, however, stop measuring vitamin D so often, and don’t be concerned about recommending 800 or 1,000 IU of vitamin D daily along with adequate amounts of calcium preferably taken as food if possible.

For more information:

Kleerekoper M. J Bone Miner Res. 1994;9:1267-1276.