Friday, January 11, 2013

Vitamin D vs Mortality Part 4

As per yesterday's post, it's important to have the right tool used for the right job, right?  Unfortunately, it's not always clear which tool is best.  For instance, there is actually still some quibbling over whether vitamin D affects mortality or not.  Many studies suggest this to be the case.  In fact, in a prospective cohort study published this month in the American Journal of Epidemiology, the authors concluded that vitamin D levels are inversely linked to all-cause mortality in both blacks & whites.

To arrive at their conclusion, the authors followed more than 85,000 women & men in the Southern Community Cohort Study for close to 8 years when possible.  Of those 1,852 who passed away during this time w/blood samples frozen, 25OH vitamin D was measured & compared to matched controls from the study.  

In general, regardless of age group 40-49yo, 50-59yo & >60yo, their average 25OH vitamin D was just over 15ng/mL or well into the deficient range.  Of course, the definitions of normal, insufficient & deficient are open to debate.  Suffice it to say that those w/25OH vitamin <10ng/mL had a significantly higher all-cause mortality compared to those whose level is >21ng/mL.  However, lowest mortality was found at >35ng/mL.

Of course the big question that needs to be addressed is whether the chicken or the egg came first.  Remember that this was a prospective cohort study, not a randomized controlled trial.  This doesn't prove anything but rather proposes hypotheses that need to be sorted out.  Perhaps, all-cause mortality is lower in those w/greater vitamin D because they spend more time outdoors exercising.  Hopefully time will tell.  We'll see.




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