The typical American drinks about a cup and a half of coffee a day.
Studies suggest that a daily caffeine habit may help protect against Alzheimer's disease. But, new research indicates that the cup or two a day that most Americans drink probably isn't enough to give any benefits. And even if you're buzzing on coffee, researchers say a person's Alzheimer's risk is largely determined by genes.
It's an appealing notion that our daily pick-me-up may also confer a range of health benefits. And for coffee drinkers there's a lot of research percolating. Several studies suggest that a daily caffeine habit may help protect against Alzheimer's disease. But there's a catch. The cup or two a day that most Americans drink doesn't seem to be enough. Researchers say 500 mg of caffeine, or about five cups of regular coffee, is the dose that seems to protect the brain.
Five Cups A Day
This may sound like an excessive amount of caffeine. After five cups, lots of us would end up with the jitters and be making extra trips to the bathroom. But some coffee lovers are hard core:
"I drink five to six cups a day religiously," says Gary Arendash, a researcher at the Florida Alzheimer's Disease Research Center, part of Florida State University. Arendash says he's convinced that caffeine is protecting his brain.
Arendash and his colleagues at the Florida Alzheimer's Disease Research Center have been studying the effects of caffeine on the brains of mice with Alzheimer's disease. They've found that adding caffeinated water to rodents' diet results in big improvements. The mice perform better on short-term memory and thinking tests. But only if they get enough caffeine.
"The human equivalent of two to three cups of coffee does not have benefits in our Alzheimer's mice," says Arendash.
Arendash's team also documented that these super-caffeinated mice end up with about a 50-percent reduction in abnormal amyloid proteins, which are thought to play an important role in the development of Alzheimer's.
The typical American drinks about a cup and a half of coffee a day. "So you can see that many of us are below that threshold level that we believe confers protective benefits," says Arendash.
Evidence Not Conclusive
The Alzheimer's mice studies on caffeine are intriguing to researchers who are trying to translate the findings into advice for humans. But interpreting an animal study can be tricky.
"It's always a good starting point," says Joan Lindsay of the University of Ottowa. "But we never know how well it's going to hold up with humans." After all, people are a lot more complicated. And researchers have learned that mice can respond really differently than humans do to a drug, an environmental toxin or a change in nutrition.
Another challenge is to find a reliable test of the memory of mice. Arendash uses a mouse maze to assess the spatial memory of his Alzheimer's mice. He puts the mice in little swimming pools with lots of alleys and dead-ends to see how quickly they can find and remember hidden escape platforms. Similar computer-based maze tests are used in human studies.
"The first thing that is lost in Alzheimer's is short term memory -- the memory for what happened a few seconds or a minute ago," says Arendash. "That's what (the water maze) is focusing on."
Observations Of Coffee-Loving Middle-Aged Folks
There wouldn't be as much interest in Arendash's mice studies if scientists hadn't also begun to gather some evidence that a steady caffeine habit is beneficial to people, too.
One recent study comes from Finland where researchers followed about 1,400 coffee drinkers for more than two decades. Researchers found one group seemed to benefit the most: the people who'd been drinking three to five cups of coffee a day in their 40s and 50s.
"They had about a 65-to-70-percent reduced risk of developing Alzheimer's disease in their 70s," says Huntington Potter, a neurobiologist at the University of South Florida. Potters says effects held up even when researchers controlled for things such as cardiovascular disease, which can influence the risk of dementia.
A few other smaller studies in Europe have led to similar findings, but experts say the research only establishes a correlation between coffee drinking and brain protection.
"I'd hesitate to say that there's epidemiologic evidence that coffee prevents Alzheimer's disease," says Reisa Sperling, an Alzheimer's researcher at the Brigham and Women's Hospital at Harvard University.
It's possible that these regular coffee drinkers might have other habits in common that could explain the protective effect. "People who are very active in mid-life are more likely to be drinking coffee than couch potatoes," says Sperling. Maybe the coffee drinkers aren't benefiting from the coffee as much as they are from keeping their minds and bodies active. The studies make it difficult to suss out.
Coffee Drinking Can't Offset Genetic Risks
Sperling says Alzheimer's is an incredibly complicated disease. Exercise and good nutrition do seem to be protective, but a person's risk is largely determined by genes. No one behavior or diet change -- like coffee drinking -- can erase that risk.
If future research brings stronger evidence that caffeine may modify the risk by some small percentage that means coffee lovers will have one more reason to drink away.
Just make sure those five cups don't keep you up all night -- sleep is important to health, too. Copyright 2010 National Public Radio. To see more, visit http://www.npr.org/.