Earlier quoted context omitted.
> It is strange to discuss L-theanine with vitamin D as one has nothing much to do with the other. That's the idea, vitamin D was used as a placebo. They bought vitamin D supplements rather than cellulose because the supplier sold both L-theanine and vitamin D and the pills looked (nearly) identical.
Vitamin D3 is not a placebo at all. It 100% promotes energy quite quickly even though it takes much longer for the body to convert it to the active form. Also, its mental effect is distinctly different from that of L-theanine, like day and night. For these reasons, it's not a great candidate for comparison with L-theanine.
Taking vitamin D once, right before bed will do nothing. Our bodies don't use it that way.
Cholecalciferol = weeks
calcidiol = hours