There are people who claim that homeopathy cured their cancer.
This is exactly the kind of bias that rational people should be scared of. This is exactly the kind of thing that we have double blind controlled studies to eliminate.
EDIT: Because if you do something, and it makes you feel good, well - that's fine. But don't go around telling other people that they're wrong and doing harm to themselves by not doing this thing.
> I know people who claim that eating a mainly paleo diet makes them feel better.
Well, there are people who claim fasting makes them feel better, too. Or living on allegedly nothing but sun light.
I am not sure this is very good proof since e.g. not eating for a couple of days makes you feel good because it's your body trying to make you more active to gather food... so, as logical as some correlations might sound it seems flimsy to me. The best way is probably to go by blood and medical exams, to see if you actually are healthier.
Though I am tempted to think it is less to do with removing diary , pasta etc and more to do with them actually eating some damn vegetables now.