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Used a $150 ZEO which monitors brain wave activity
A lower cost unit uses a Smartphone
He looked at many different sleep parameters
The vitamin D analysis is about 2/3 the way thru the very long web page
At night had 5,000 IU vitamin D or placebo pills (one subject: double blind)
Takes 5,000 IU vitamin D the next morning if he discovered that the previous evening was a placebo
Extremely scientific, even includes the software code for the analysis on the web page