After 40 days and 40 nights (plus a few), I’ve finished my little randomized double-blind placebo-controlled vitamin D sleep experiment: http://www.gwern.net/Zeo#vitamin-d
Conclusion: it probably hurts sleep when you take it at night.
Followup: it helps morning mood when taken in the morning: http://www.gwern.net/Zeo#vitamin-d-at-morn-helps
After 40 days and 40 nights (plus a few), I’ve finished my little randomized double-blind placebo-controlled vitamin D sleep experiment: http://www.gwern.net/Zeo#vitamin-d
Conclusion: it probably hurts sleep when you take it at night.
Followup: it helps morning mood when taken in the morning: http://www.gwern.net/Zeo#vitamin-d-at-morn-helps