The study began with a question: why has previous research found that coffee consumption correlates with lower risk of developing neurodegenerative diseases like Alzheimer’s and Parkinson’s?
“We wanted to investigate why that is—which compounds [in coffee] are involved and how they may impact age-related cognitive decline," said lead study author Dr. Donald Weaver, co-director of the Krembil Brain Institute in Toronto.
To find out, the research team evaluated several compounds (including caffeine) released during the roasting process in three types of coffee beans: caffeinated dark roast, caffeinated light roast, and decaffeinated dark roast.
The analysis focused on how the compounds interact with amyloid beta and tau, the toxic proteins linked to the development of Alzheimer’s disease. Results from previous studies suggest that coffee compounds could provide a neuroprotective effect by preventing these proteins from forming the terminally disruptive clumps and tangles found in the brains of Alzheimer’s patients.
The researchers gradually zeroed in on one particular set of compounds known as phenylindanes that form during the roasting process and give coffee its paradoxically enjoyable bitterness. More than any other compound of those examined in this study, the research team found that phenylindanes inhibit both amyloid beta and tau under laboratory conditions.
"So phenylindanes are a dual inhibitor…we were not expecting that," said Dr. Weaver.
The researchers added that most likely it’s a combination of compounds that provides the biggest benefits from drinking coffee, but the results indicate that phenylindanes—present in both caffeinated and decaf coffee (slightly more in dark roasts)—are central to its neuroprotective effects.
Since this was a lab study that examined the interaction of coffee compounds with toxic proteins outside the body, the next step is to find out if the same results turn up in human subjects once ingested. While the results aren't conclusive, the research is an important starting point to investigate how these compounds interact with proteins responsible for brain-destroying diseases that affect more people every year. The researchers were careful to note that they aren't suggesting that coffee is a cure for these diseases.
"What this study does is take the epidemiological evidence and try to refine it and to demonstrate that there are indeed components within coffee that are beneficial to warding off cognitive decline," said study co-author Dr. Ross Mancini. "The next step would be to investigate how beneficial these compounds are, and whether they have the ability to enter the bloodstream or cross the blood-brain barrier.”
Forbes
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