Shift happens

The current issue of the blue journal has more stuff on the vitamin D hypothesis (that has been shifted recently into the opposite direction). I agree with the editorial that

Intervention studies of vitamin D in the primary prevention and treatment of asthma raise a number of difficult scientific, ethical, and regulatory issues.

That may be true while the editorial includes the widely quoted myth that immunological effects occur only at high doses (at least it provides no good reference). And sure, I am misquoted with effects on Th2 (never said that) as well as on asthma (so far I talked only about sensitization).

Without dietary supplementation, humans obtain about 90% of their vitamin D from sunlight exposure and 10% from diet

is also not correct as a newborn will get 99,5% from sunlight. On the other hand I liked the note that

humans cannot overdose on vitamin D from sunshine because excessive pre–vitamin D is destroyed by sunlight to inactive photoproducts, and repeated exposures stimulate tanning. This does not happen with dietary vitamin D, where there is clear potential for overdosing.

For those who have not attended the recent session of the AAAAI in Washington, here is a possible and rather simple explanantion of the Weiss et al. findings. Supplements may be more effective in hypovitaminic individuals, yea, yea.