When coffee beans are roasted, they make some natural compounds that, in lab tests, stop harmful clumps of brain proteins from forming—clumps that are linked to Alzheimer’s disease. One of these compounds, called phenylindane (6), was super effective at stopping these clumps.

When coffee beans are roasted, they make a chemical called phenylindane that might stop harmful clumps in the brain—linked to Alzheimer’s—from forming, at least in test tubes.

Dark roast coffee has a special compound that might stop two harmful proteins in the brain from clumping together, which could be good for brain health.

A compound in coffee called quercetin might stop some harmful protein clumps linked to Alzheimer’s from forming, but it doesn’t stop another type linked to tau, and at high doses, it might even make a different protein clump more — so its effects are mixed and not simple.

Dark roast coffee seems to stop harmful clumps in the brain better than light roast coffee, and scientists think it’s because the darker roasting creates special compounds called phenylindanes.