After reviewing my first blog entry on vitamin D, I came across a riveting hour-long YouTube post from some budding videographers at The Centers for Disease Control. And while the editing and composition leave something to be desired, there were some useful pearls that I will reveal here (and save you the burden of having to watch it yourself).
Four points emerge from the presentation, given by experts from several branches of the National Institutes of Health:
- There are only two systematic reviews (from 2008 and 2010) of vitamin D and its benefits. Both conclude there are no data to prove or disprove claims that D can influence the course of heart disease, cancers, hypertension, pregnancy outcomes, or death rates in general (cheerfully referred to as “all-cause mortality”).
- The existing recommendations on D blood levels and intake come from an Institute of Medicine report from 1997. That’s OLD research. The recommendation of 27.5 nmol/L was only intended to prevent rickets and other severe deficiency states. Because of this, other organizations have stepped in with their own guidelines — some as high as 80 nmol/L — though no one is sure which is correct.
- Because no one knows what the correct blood level should be, the scope of the deficiency problem cannot be defined. For example, if we use the 27.5 nmol/L level, less than 6% of the US population is deficient. But raise that to 80 nmol/L, and all of a sudden that figure rises to more than 70%.
- The assays to measure D levels have changed dramatically over the past 15 years, and no one is sure which one is the most accurate.
As the Director of the Office of Dietary Supplements, Dr. Paul Coates, succinctly stated:
“I don’t know what number to tell people to shoot for… oh, and I don’t know that that number is reliably measured. It may be, but I don’t know that.”
Donald Rumsfeld could not have spoken any more clearly.
For now, I think the most reasonable recommendations are:
- 400 IU daily in children
- 400-800 IU daily in men and women < age 50
- 800-1000 IU daily in men and women > age 50.
We’ll see what the next Institute of Medicine report advises. Try not to lose any sleep in the meantime.