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.

Quercetin, a natural compound, might help stop harmful clumps linked to Alzheimer’s, but barely affects another type linked to Alzheimer’s, and could actually make clumps linked to Parkinson’s worse at higher doses — so it’s not a safe all-purpose brain protector.

Some chemicals in coffee, like caffeic acid and quercetin, might make a harmful protein clump together in the brain at high doses, which could make Parkinson’s disease worse — but other coffee chemicals don’t do this.

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.