I just updated VeganHealth.org/articles/bones with the following tidbits:

Dr. Jacqueline Chan sums up the studies on vitamin D2 vs. D3, “Treatment for most of the studies finding D2 to be less effective than D3 were extremely large boluses given only once, whereas in studies finding them equally effective, the treatment was daily amounts between 400 and 2,000 IU.” (38)

Test Kit

The Vitamin D Council has partnered with ZRT Labs to make a discounted take-home vitamin D test kit available (for $65 as of April 2010).

Sun Tips

According to Dr. Jacqueline Chan, in order to make vitamin D, “The sun must shine directly on skin without being blocked by sunscreen, glass and most plastics. Glass and most plastics block UVB, the part of the spectrum that converts pro-vitamin D3 but allow passage of UVA which contributes to skin cancer.” (38)

Also according to Dr. Chan, increasing the surface of the skin exposed to the sun proportionately decreases the amount of time needed in the sun to produce the same amount of vitamin D. The duration of the sun exposure should be no more than about half the amount of time it takes for the skin to turn pink. (38)

I have also been getting the impression, based on hearing from people who have been supplementing and getting tested regularly, that it could take large amounts of vitamin D2 (1,000 – 2,000 IU per day) over the course of months to see a significant increase in 25(OH)D levels.

References

38. Vitamin D Update for Nutrition Professionals. Chan J. Vegetarian Nutrition. Volume XVIII, Number 1 and 2, 2009:1.

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