What the studies show, what they don’t, and a study of our own where nobody has run one.
Every claim gets a grade, and nobody here types it. We record each study — its design, its size, who paid for it, and whether the claim was what the study set out to test — and a fixed set of rules turns that into one of six grades. To change a grade, the evidence has to change. How we grade.
Where a popular claim has never been tested, we say so, and where we can, we run the test — registered in advance, published whatever it shows.