Diacetyl, a flavoring used to produce the buttery flavor and aroma of microwave popcorn and other food, may be linked to Alzheimer's, U.S. researchers say...Vince's team said it realized that diacetyl has an architecture similar to a substance that makes beta-amyloid proteins clump together in the brain — this clumping is the hallmark of Alzheimer's disease. Other laboratory experiments also showed diacetyl easily penetrated the "blood-brain barrier," which keeps many harmful substances from entering the brain, Vince said. "In light of the chronic exposure of industry workers to diacetyl, this study raises the troubling possibility of long-term neurological toxicity mediated by diacetyl," the researchers said in a statement.