of disease, but that’s not the same as showing that if you start eating more oatmeal, your risk will drop. To prove cause and effect, we need to put it to the test by performing an interventional trial: Change people’s diets and see what happens. Ideally, researchers would randomly split people into two groups and give half of them oatmeal and the other half a placebo—a fake, similar-tasting and -looking oatmeal. Neither the study subjects nor the researchers themselves can know who’s in which group until the end. This robust, double-blind
