Ask HN: Getting Vitamin D from Mushrooms

Being a hacker and living in the Pacific Northwest, I don't get enough sun and am probably deficient in vitamin-d. I have read some articles that say mushrooms produce a healthy dose of vitamin-d when exposed to ultraviolet light. Is it just a matter of buying a blacklight and shining it on regular mushrooms that I get from the local grocery store for some period of time, before I cook them up? I haven't seen mushrooms advertised as UV-enhanced or high-in-vitamin-d in any of the stores I normally shop at, so I'm considering the do-it-yourself strategy.