Replies to post #135256 on Biotech Values

[NP1986]

I don't think it's fair to make assumptions about what vitamin D supplementation would do to CRP levels based on this type of study. There could be variables that affect both serum 25-Hydroxyvitamin D levels and CRP that weren't accounted for. And as you said, they didn't look at actual CV outcomes.

There's a large randomized trial of vitamin D supplementation that is ongoing which should provide some clarity in terms of its effects on CV outcomes.

[randychub]

Hey Dew - Would you happen to have the full article or a link to it?

Randy

[hiddenflem]

Hi Dew, The vitamin D study was observational and cross sectional; inferences from the study about direction of effect or about what supplementation would do to CRP levels are completely speculative in my opinion. I've seen studies of a number of other adverse health outcomes out there showing U shaped relationships with 25(OH)D. The reasons for this are not clear but it very well may be residual confounding; people with high levels might visit their doctor more often for other health conditions (for example) therefore having their vitamin D levels checked and being treated with high dose supplements. Or possibly people with high levels in the study may have some differences in the metabolism or storage of vitamin D. In this study they didn't adjust for season of blood draw or geographical location-- am not sure why since presumably they had that information since it came from NHANES.

On a side note I'm not sure I would classify 20ng as rock bottom either; though I personally side with the view of Hollick and other experts that higher levels are desirable, there are some out there who think that 20ng is an appropriate target level for the general population including the IOM committee responsible for the RDA who used that as the target level sufficient to meet the needs of 97.5% of all Americans. Which was admittedly quite a contentious recommendation.

[hiddenflem]

Another study just came out looking at vitamin D and hypertension/CVD mortality in NHANES; no increased risk of CVD with higher levels of vitamin D.

Zhao G, Ford ES, Li C, Croft JB. J Hypertens. 2012 Feb;30(2):284-9.
Serum 25-hydroxyvitamin D levels and all-cause and cardiovascular disease mortality among US adults with hypertension: the NHANES linked mortality study.

Of 2609 participants with hypertension, 191 died (including 68 CVD deaths) during an average of 3.7-year follow-up. Compared with participants with 25(OH)D concentrations in the highest quartile (=29?ng/ml), the hazard ratios for all-cause mortality were 1.93 (95% CI 1.06-3.49), 1.32 (95% CI 0.85-2.04), and 1.36 (95% CI 0.84-2.22), respectively (P for trend <0.05), and the hazard ratios for CVD mortality were 3.21 (95% CI 1.14-8.99), 2.42 (95% CI 0.85-6.90), and 2.33 (95% CI 0.88-6.12), respectively (P for trend <0.05), in the first (<17?ng/ml), second (17-<23?ng/ml) and third (23-<29?ng/ml) quartiles of 25(OH)D after adjustment for potential confounding variables. Additionally, concentrations of 25(OH)D as a continuous variable were linearly and inversely associated with the risk of mortality from all causes (P?=?0.012) and from CVD (P?=?0.010). These relationships were not affected much by adjustment for baseline blood pressure and use of antihypertension medications.