First - CONGRATULATIONS are in order. Astute reader Bill Spaeth (Team Raven Lunatics, Arcata, CA, sponsored by FSM) aced the competition in my recent T shirt contest by correctly deducing that an athlete laboring mightily in the sunfree Northwest might be supplementing with Vitamin D. Nice work, Bill!
Yes, sports fans, I've been sucked into the dark, dark world of sports supplements. But - Oregon is a dark, dark place, especially in winter. In fact, ANY place at a latitude above 40-42 degrees is unlikely to provide enough solar radiation to produce sufficient Vitamin D in the winter months. Salem, Oregon sits at precisely 45 degrees North latitude. Add in that current knowledge about skin cancer and UV damage lead most of us to be very careful in using sunscreen, and there are a lot of Vitamin D deficient people out there.
Vitamin D does a lot in the body other than "just" maintaining healthy bones. I'm already on the hook for crappy bone density - family history AND a lot of cycling (non-weightbearing exercise) predispose me - so I'm grateful for all the help I can get in the bone density department. But - in addition to that, there's good evidence that Vitamin D helps improve athletic performance and is protective against some autoimmune disorders and cancers. It has a very wide range of effects in the body - it's one of the fat-soluble vitamins that acts as a hormone in the body.
The research on this subject is pretty solid. If you'd like to get a look, you can type "Vitamin D athlete" into Google Scholar. (OH! You didn't know that Google has a "scholar" setting? Pretty cool - it ONLY returns peer-reviewed/journal-published information. Pull down "Scholar" from the "more" clickdown on your Google homepage...voila! Just the information you're looking for, and no commercial sites or "junk" science.) Or you can get some great information here: http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/ (written by Dr. Jane Higdon, with lots of references).
The current issue of OUTSIDE magazine has (in addition to a vaguely interesting interview with Jack Johnson) a good "popular science" type review of Vitamin D's uses in the body, and how we're likely not getting enough.
Sun exposure provides a HUGE amount of Vitamin D relative to food. A few minutes' exposure to the sun a couple of times a week provides several THOUSAND IU's (international units) - again, provided that the sun angle is correct to give you exposure to the UV-B wavelength which is necessary for synthesis. There aren't many foods that are high in D, and some of them, like cod's liver, just aren't a regular staple. An egg - a food that's on the recommended list for Vitamin D - packs in 20 IU. The RDA is 400, and current research shows that that's almost certainly much lower than is desirable for optimum health.
So - since the best available medical advice on sun exposure is still "don't", it almost becomes imperative to supplement your diet to make sure you get enough.
I've been taking 1000 IU once or twice a day since November. I can't swear that there's any difference, but I don't feel like I had the performance dropoff that I normally have in the winter, either. I bought a jar of 250 caps (250 x 1000 = 250,000) and as it turns out, I'll swallow the last one Friday morning on my way out of town.
Next post: WHY I'm the luckiest person in the world. Promise.