Your question about popcorn is a great one. I personally had to remove corn from my diet as I found I had digestive problems when I consumed it. If corn does not give you any problems I would suggest purchasing organic popcorn and making it yourself in an air popper as this is the healthiest way to consume popcorn. The reason I suggest organic popcorn is because corn is one of the highest genetically modified foods on the market. GM foods create a whole host of problems in the body and as a result consumers feel many side effects.
I hope this helps. If I can be of any further help please reach out to me.