Sunday, December 30, 2007

Getting a D in Health

Greetings, indoor, computer-reader.

The Sunbathing Ape

It's natural for us to feel drawn to amazing photographs of sun-soaked landscapes. We humans evolved as mostly-naked, outdoorsy folks in sunny Africa. Although the cultures (and to some degree the genes) of migrating peoples have done what they can to adapt to more polar environments, if you dig at all deep into our biology you'll see we still aren't fine-tuned to live indoor, boreal lives.

One of the biologically unmet expectations humans in the USA and Canada experience is low sun exposure, leading to Vitamin D deficiency. This article in the Globe and Mail suggests that Canadians typically have about one third of optimal concentrations of vitamin D in their bloodstream.

What's D Good For?

Until recently, it was thought that the major effect of vitamin D deficiency was rickets. Since (last time I checked) rickets wasn't an endemic problem to North Americans, vitamin D was seen as being a non-issue; the mandated additions of D and A to dairy products seemed to be sufficient to keep bone formation normal in children.

However, vitamin D has more functions than merely the regulation of bone density. It's also an important chemical precursor to a lot of important cellular signaling mechanisms: not having sufficient vitamin D is the equivalent of trying to run a government when there's a shortage of notepads to write on.

D and Cancer Rates

One of the worst consequences of screwing up chemical messages is to impede natural anti-cancer cellular mechanisms. Does our D-prived culture result in fact in increased cancer rates? The only way to know for sure is with a double-blind experiment where groups are given vitamin D and placebos at random, and to track prevalence of cancers in the two groups. That's exactly what this study did, and what they found is almost unbelievable. Giving 1.5g supplemental Calcium with 1100 IU per day (about 3 liters of milk worth, but the study used pills) decreased cancer rates by 77% after one year.

Great moons of Neptune! That's a huge decrease! The cautious part of me finds it hard to believe that one factor could be responsible for over half of cancers, and to be fair the study tracked only 1200 women over 4 years, and thus wasn't able to notice enough cases of cancer to have really tight confidence intervals: the range of cancer decreases still consistent with the study is 91%-40% 19 times out of 20. Still, I've started feeding vitamin D to my wife as well as taking it, if not daily, than at least often.

Public Health Consequences

Suppose the study's numbers bear up, and that about half of cancers could be prevented by 1100 IU of vitamin D per day. Would it be a good policy for health insurers (or friendly socialist governments like Canada's) to simply hand out vitamin D supplements? It looks like the cost of vitamin D is pretty much nothing: this bottle of 250 pills (almost a year's supply) with 1000 IU of vitamin D is only $10. On the flipside, the annual cancer rate in the US is 1 in 200. If that could be halved by the D supplement, and if treatment costs on average $40 000, that's an expected savings of $100 per year. Pay one dollar into prevention, get 10 out in unneeded treatment. (Oh, then there's the whole increase in lifespan and quality of life issue too.)

Last Word

I suppose the cautious policy approach would be to conduct a larger study to figure out where within the wide confidence interval the truth lies. However, I'm inclined to start ramping up vitamin D production and consumption programs, maybe even with heavy subsidy by governments, HMOs or otherwise. Let's get a D in health.

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