I've seen a lot of claims, some referring to "research" others not. As some have pointed out - there is NO way to do an objective, controlled scientific study. Another thing to keep in mind when looking at "statistical studies" - there are three kinds of liars: liars, damn liars, and statisticians.
Best to just find something that works for you and give 100% to that and not worry about other approaches. As long as it works for you, you're golden. As an analogy: I have allergies. My Dr. tried many meds to get them under control. None worked till he hit on the one that worked for me. I can't fault the meds that didn't work for me. They work for a lot of people, just not me. Once I found the med that aleviates my allergies I had my relief. No need to worry about the other meds. Just keep taking the one that works for me and no more suffering.