Vitamin D3 During Pregnancy and Cognitive Performance at 10 Years

Meanwhile, the endocrine society is still murdering millions by asking people to not supplement vitamin D3 and to explicitly not test for it either. The times must be tough for endocrinologists with people supplementing high-dose vitamin D3 and testing routinely to ensure an optimal level, tough enough to want to keep people very sick.

Can you say p-hacking? It was designed and powered to test whether prenatal vitamin D reduces childhood asthma/wheeze, and found no effect on that primary outcome. The rest is just shuffling numbers and statistical methods around until something with p > .05 pops out.

They flags their own post hoc status, reports modest effect sizes, and applies some multiple-comparison correction. That makes the rhetorical sleight of hand harder to spot, because it's buried inside otherwise careful looking work.

The statistics are shit. They applied Benjamini-Hochberg FDR correction within cognitive domains, not across the family of 11 functions. That choice is what produced the headline "memory survived correction."

Watch what happens with the actual numbers. The two "winning" functions, verbal memory (p = .02) and visual memory (p = .01), both sit inside the memory domain — which contains exactly those two functions. BH within a 2-member family barely adjusts anything: the most lenient threshold is just 0.05, and both p-values are already under it, so the q-values come back at .02 and .02. The correction was toothless by construction, because the two hits happened to fall in the same tiny domain. A reviewer should have made them show the whole-family result side by side. The fact that they didn't is the tell. And there is much more that could be criticized in the same manner across the whole thing.

And then the observational data fail to corroborate the supplementation finding. The authors explain the mismatch via trimester timing of exposure, which is plausible, but the equally plausible reading is that the RCT hits are fragile, or that, more probably, it's not a real effect.

And even if there was an effect, it's so small and weak and NOT proven by even this data, that the recommendation for supplementation is not warranted at all. At best, this single study with their focus on recreating this effect is the only defensible conclusion. And yet they recommend supplementation.This is pure bias and D-vitamin cult babble once again.

The conclusion, based on the actual data, is: in a vitamin-D-sufficient cohort, high-dose prenatal D3 was not associated with offspring cognition on any whole-battery-corrected measure.

I hate this so much because it's stupidity like this that shows that science is not worth paying attention to, because the scientists basically lie through their teeth, at least from my perspective, where truth is something that is verifiable and relates to something real.

the Vitamin D cult is a bit insane

it is -exactly- like Linus Pauling and Vitamin C cult in the previous century

Vitamin D is very important

Too Much is as bad as Too Little

The "RDA" is too low at 600IU and should have been changed to 2000IU decades ago

It can help prevent certain diseases and illnesses

It CANNOT cure any known disease or illness once afllicted

I just skimmed the summary but in the results section it reports three significant results and two after “multiple-test correction”. I’m not sure how they did that correction; I would expect that measures of cognitive performance are correlated for each child and so the standard Bonferroni correction might be too harsh to apply here.

> Covariate-adjusted analyses of standardized scores (mean [SD], 0 [1]; higher values indicating better performance) showed positive associations of high-dose vitamin D3 with verbal memory (β = 0.17 SD; 95% CI, 0.03-0.32 SD; P = .02), visual memory (β = 0.24 SD; 95% CI, 0.06-0.42 SD; P = .01), and flexibility or set shift (β = 0.19 SD; 95% CI, 0.01-0.37 SD; P = .04); however, high-dose vitamin D3 was no longer associated with flexibility or set shift after multiple test correction.

> We found that high-dose supplementation was positively associated with 3 of 11 functions assessed: verbal memory, visual memory, and flexibility or set shift. However, the association with flexibility or set shift was not significant after correction for multiple testing.

They tested 11 different measures. Only 3 of those tests showed significance, but after they corrected for multiple testing the significance of 2 of those disappeared. Only 1 test remained below the significance threshold.

This is on a set size of about 500 children who completed the study, randomized to the two groups.

The only measure that remained statistically significant was visual memory. If you look at Figure 2 it's not even clear that there was a trend toward improvement because everything is so scattered, including a couple measures that were trending worse with higher Vitamin D levels.

This study isn't very convincing. It's a classic p-hacking trick to include many different smaller tests so if one of them pops up as an outlier you can claim that something was significant.