When you complain that circumstantial situations can effect the results of a study, this is why anecdotal evidence is not useful and not why actual studies aren't useful.

I am not saying they are not useful. I am saying that they can be flawed.

This is the very reason scientist try to include as many subjects as possible - to average out or otherwise eliminate other possible factors.

Actually they rather try to focus on one single thing.

Furthermore no scientists takes one study and says "done." Instead they expect other studies to try and reproduce the results.

no. they don't. most scientists can't replicate studies from their peers.

http://www.bbc.com/news/science-environment-39054778

Unfortunately the problem is media reporting that take a single study and make a catchy click-baity headline from it. This is why you don't hear doctors stating that any of the items you listed cause cancer, because the results have not been consistently reproduced. What you're hearing are pop-sci hacks.

That's a different kind of blue-pill all together and yes I agree.