I found that taking a specific brand of Vitamin D (the Genestra D-mulsion in particular) right before bed was guaranteed to give me vivid dreams. I've had half a dozen friends try it, with every single one reporting similar results.
I checked the ingredients. That is because it contains glycerin. Which is a great and safe supplement to take for anyone with sleeping issues. But will cause very vivid dreams at the start. D3 will not by itself have a huge effect on dreams.
That's interesting. I know vitamin D can improve sleep quality in people who are deficient, and sleep quality helps with dream recall -- I wonder if that's the mechanism or it's something else.
A cursory search shows lots of redditors taking Vitamin D (some of them way, way too much btw) and having wild dreams too.
I take 800IU a day and haven't noticed anything on that little.
Supplementing any "large" amount of either Vitamin D or Bs really messes with my sleep. It makes it harder to fall asleep and I get crazy dreams (and sometimes hallucinations in bed too)
Spicy food and dehydration do wonders for me!
I've heard not to take vitamin D right before bed because it will kinda keep you up. Maybe the vitamin D as a stimulant is what's gives you the extra dream awareness.