JK, I had subtle, yet adverse reactions to various supplements that would make sleep very difficult for me. Once I stopped taking these, I would fall asleep so much easier. This is going to be different for everyone but the things which effected my sleep were: Betaine, Milk Thistle, Methylcobalamin, turmeric, and to a lesser extent, selenium and iodine.

Many of these supplements didn't affect me adversely in the daytime, yet had very noticeable effects (individually) on my sleep patterns. Once I stopped them I could sleep so much better, and if I introduced any one of them I would have a hard time sleeping, specifically falling asleep after waking up around 1-2am.