Activated charcoal toothpaste doesn't whiten teeth as well as other options—some studies found no whitening difference at all compared to regular toothpaste. The bigger concern: it's significantly more abrasive, which means it can wear down your enamel over time.

Researchers reviewed 11 published studies (out of 208 articles found) that tested activated charcoal toothpaste on real teeth or extracted teeth to measure both whitening ability and abrasiveness.

Funding not disclosed in abstract