Coffee and cigarettes could protect the brain of flies with a form of Parkinson's disease, but the benefit was not because of caffeine and nicotine, says a new study.
Leo Pallanck, a neuroscientist at the University of Washington in Seattle, whose team led the new study, said that if they could identify the compounds that put up this brain defence, they could offer a preventive Parkinson's treatment where none currently exists.
"We think that there's something else in coffee and tobacco that's really important," New Scientist quoted him as saying.
Epidemiological studies have suggested that coffee-drinkers and smokers are less likely to develop Parkinson's than abstainers.
"A lot of the field has gravitated to the idea that it's caffeine and nicotine [that protects their brains]," said Pallanck.
To see if ingredients other than caffeine and nicotine might be providing the benefit, Pallanck's team turned to fruit flies with a condition similar to Parkinson's disease.
The flies have mutations that kill off dopamine-producing neurons, which causes them to develop movement and cognitive problems like those characteristic of Parkinson's in people.
The same mutations are linked to hereditary forms of Parkinson's in humans.
The researchers prepared several fly foods spiced up with normal coffee, decaffeinated coffee, smokeless "dipping" tobacco designed to allow nicotine absorption via the mouth, or a commercial nicotine-free tobacco.
Then the researchers raised groups of flies on the various diets.
Normally, dopamine-producing neurons in the mutant flies die off as they age.
However, a diet featuring coffee and tobacco kept the neurons alive in all the flies tested at 20 days old, whether or not their food contained caffeine or nicotine.
In addition, when pure caffeine or nicotine were added to the meals of other groups of flies, their dopamine neurons died off - just like those of flies whose food had no additive at all.
"We didn't see any protective effects at all of caffeine and nicotine," said Pallanck.
His team went on to identify a compound found in both decaf and normal coffee called cafestol that seems partially responsible for its neuro-protective effects.
Cafestol activates a protein produced by flies called Nrf2, and the team found that blocking Nrf2 diminished coffee's protective effect on dopamine neurons.
Blocking Nrf2 in flies fed tobacco also reduced its protective effects.
And now, the scientists are searching for tobacco ingredients that activate Nrf2 - and other ones that do the same in coffee.
These compounds might one day be given to people to protect against Parkinson's.
Alternatively, new drugs could mimic the protective neural processes triggered by coffee and cigarettes.
The study was published in the Journal of Neuroscience.