Reducing Adrenaline/epinephrine In The Brain/body
I've experiencing some anxiety lately which I believe could be a build-up of adrenaline in the brain/body (if this is actually a thing). I'm looking for ways to reduce the amount of adrenaline. One of the reasons why I think it's a build-up of adrenaline is that I've (on a few occasions) taken a small amount (10mg) of propranalol and it clears up any issues almost immediately. I understand that one of the things that propranalol does is lower adrenaline levels in the brain (https://newrepublic.com/article/133008/cure-fear).
However, I'm looking for something a bit more "natural". The only other things I've come across are niacin potentially (http://www.doctoryourself.com/hoffer_niacin.html) and exercise (seemingly anecdotal claims only, no empirical evidence that I've been able to find).
Are there any other substances or strategies that help to reduce adrenaline. I'm sure something like meditation would as well although I haven't found empirical evidence on that either.