It is fine to see another group of researchers who get it, even if it takes them five years to rediscover what others have already discovered. This time it has to do with the dose of vitamin D needed to get the elderly above 30 ng/ml. Dr. Leidig-Bruckner and five colleagues from the University of Heidelberg simply went back and looked at the records of 104 patients treated with varying doses of vitamin D.
Leidig-Bruckner G, Roth HJ, Bruckner T, Lorenz A, Raue F, Frank-Raue K. Are commonly recommended dosages for vitamin D supplementation too low? Vitamin D status and effects of supplementation on serum 25-hydroxyvitamin D levels–an observational study during clinical practice conditions. Osteoporos Int. 2011 Jan;22(1):231-40.
First, they rediscovered what Professors Heaney and Vieth discovered years ago, 1,000 IU of vitamin D a day does not move 25(OH)D levels very far (about 10 ng/ml) and even 3,000 IU/day fails to get many elderly patients with osteoporosis above 30 ng/ml.
Secondly, they rediscovered that response to any dose of vitamin D depends on the baseline level. That is, if your baseline level is 10 ng/ml, and many of these patients had such levels, then 1,000 IU/day of vitamin D will increase levels about 10-15 ng/ml. However, if your starting level is 25 ng/ml, then an extra 1,000 IU/day will only increase your level by about 5 ng/ml. In fact, the effect size continues to decrease as you go up the ladder until a baseline of 80 ng/ml hardly moves up when one takes an extra 1,000 IU per day.
Finally, they rediscovered that a commonly used biomarker of vitamin D deficiency elevated parathyroid hormone (which puts the owner at risk for multiple diseases) does not return to normal until vitamin D levels exceed 40 ng/ml. Several patients with levels above 30 ng/ml still had elevated parathyroid hormone.
Of course, elevated parathyroid hormone is simply a convenient biomarker. The important biomarker, the one the species depended on for survival, is the level of vitamin D needed to transform breast milk into a rich source of vitamin D. Someday, I hope not too long from now, a group of scientists will rediscover what Professors Hollis and Wagner recently discovered, and that is that it takes a vitamin D level of about 50 ng/ml to consistently transform breast milk into a reliable source of vitamin D.