Now comes a sobering report.
In a study evaluating 1,445 people, scientists found that consistently drinking one to two cups of coffee each day is associated with a significant reduction in the risk of mild cognitive impairment (MCI) -- a precursor to dementia and Alzheimer's -- compared to those who never or rarely consumed coffee. That supports previous work, published in 2010, that showed that caffeine may have a neuroprotective effect.
The surprise was that participants who increased their consumption over time saw their risk of mild cognitive impairment shoot up significantly. Those who went from one cup to more than one cup had twice the rate of MCI as those who reduced their drinking to less than one cup and 1.5 times the rate of MCI as those who continued to drink one cup a day.
The research, which involved participants in the Italian Longitudinal Study on Aging and were ages 65 to 84-years-old, was published in the latest issue of the Journal of Alzheimer's Disease.
The results suggest that "cognitively normal older individuals who never or rarely consumed coffee and those who increased their coffee consumption habits had a higher risk of developing MCI," co-authors Vincenzo Solfrizzi and Francesco Panza, researchers at the University of Bari Aldo Moro, wrote.
Coffee's impact on the brain has been a critical question for modern-day nutrition scientists as coffee consumption grows with many billions of cups of the stimulant are now consumed each year.
One hypothesis the authors of the Italian floated is that coffee may work by reducing inflammation in the brain. Another is that it could be activating adenosine A2A receptors which play a role in oxygen consumption and blood flow. They wrote that they believed a steady stream of caffeine may be required "for normal memory performance" and increasing or decreasing consumption may result in impaired memory functioning.
A third explanation is based on the simple fact that caffeine is a powerful psychoactive stimulate. "Caffeine could in part compensate the cognitive decline in older individuals because its effects on vigilance and attention, mainly in situations of reduced alertness," they said.