Re: getting vitamin d in winter

I believe radiation from Sun-like sources is dose dependent before it's considered harmful, much like most drugs, foods, etc...

Why are you trying to get Vitamin D?!

Most tanning beds are calibrated to 95% UVA, not the UVB bands required for Vitamin D synthesis. UVA causes the skin to tan, UVB causes skin burning after too much exposure. If you must tan, ask if they can re-calibrate the bed for you to increase the UVB spectrum between 270 and 300 nm. Vitamin D synthesis supposedly peaks between 295 and 297 nm. Even if the tanning bed is not calibrated, you're still getting 10% or less UVB.