Vitamin D

[caryn]

A new study and a review of studies out this month just killed the vitamin D idea. Or at least, they really ought to. I imagine there is still research in the pipeline, but I can't imagine there being a lot of new proposals after these:

http://www.ncbi.nlm.nih.gov/pubmed/22336906
There was no significant difference in the median serum vitamin D MoM or raw values within the outcome groups (P=141 and P=0.231, respectively) whereas the median PAPP-A MoM, uterine PI MoM and MAP MoM were significantly different (P=0.031, P=0.001 and P<0.0001, respectively)...

In other words, our D levels are average at the end of the first trimester. But other stuff is clearly already broken. So it's not causal.

and

http://www.ncbi.nlm.nih.gov/pubmed/22336854
Vitamin D supplementation in a single or continued dose during pregnancy increases serum vitamin D concentrations as measured by 25-hydroxyvitamin D at term.

In other words, *that's the only thing it seems to do*. It doesn't affect rate of onset of anything, it doesn't improve outcomes, but when you check the bloodwork, supplemented women have more vitamin D in the bloodstream.

No one would say this data completely rules out the possibility that supplementing vitamin D might help. But that doesn't mean that it is at all likely to help. It means, instead, that science can't prove a negative. If D were going to be a significant tool in our toolbox, we would see some differences in serum D levels in our population early and raising D levels would lower risk.

I'll probably write up a bit more on this for the main blog in a bit!

[alviarin]

I don't know, I haven't given up on vitamin D yet. (Though I should admit I"m probably biased since I found out I was vitamin D deficient).

One small study found woment taking 4000IU/day (higher than any previous study) had lower rates of pregnancy complications and pre-term birth. http://www.cnn.com/2010/HEALTH/04/30/vi ... index.html
I would love to get my hands on the original study, all I can find is http://www.ncbi.nlm.nih.gov/pubmed/21706518.

And please, to anyone else reading this, don't start taking large doses of vitamin D without talking to your doctor and testing for a deficiency first. Since too much vitamin D can be toxic.

[caryn]

What worries me about that one is that better pregnancy outcomes weren't reported as a study finding, in the abstract. A possible difference in frequency between the populations - and the populations were probably too small to have this be statistically significant, given the sample size - got mentioned to the journalist, who wrote all about it in the CNN article. But the science just says that more vitamin D supplementation led to higher levels of serum D.

http://www.ncbi.nlm.nih.gov/pubmed/21040394 Is a study in a high risk population that found no difference in outcomes based on serum D levels. But I am also biased, because my serum D is normal.

[alviarin]

Yeah, but how many women were in the study? If n=221 is that the total number? And if 78% of the women in the study were vitamin D "insufficient" it doesn't sound like there were very many women in the sufficient group to compare too.

Definitely an area that needs more study though, imho.

[caryn]

Yep, n=221 high risk patients - IIRC women with a history of PE - and no differences in PE rate btwn normal, mildly deficient and very deficient patients. The idea was that if vitamin D mattered we'd see differences in outcomes in a high risk population.

Big multi center randomized trials are so expensive that what we really need is a good mechanism.