MARY LOUISE KELLY, host:
This is MORNING EDITION, from NPR News. I'm Mary Louise Kelly.
RENEE MONTAGNE, host:
And I'm Renee Montagne.
In Your Health today, we examine things that may or may not have a beneficial effect on your brain - from Mozart to coffee. We start by looking at whether a daily cup of coffee does more than just perk you up in the morning. New research on caffeine is hinting at all kinds of potential benefits, from cancer protection to staving off diabetes and brain diseases. NPR's Allison Aubrey looks at the science behind the claim about Alzheimer's protection.
ALLISON AUBREY: Five cups of coffee a day may sound like may sound like an excessive amount of caffeine. I can only imagine the jitters, the trips to the ladies' room. But for neuroscientist Gary Arendash, this is his normal consumption.
Dr. GARY ARENDASH (Neuroscientist): Five to six cups of coffee a day, religiously. I truly do.
AUBREY: Why so much? Arendash is convinced that caffeine protects his brain. He 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, and they found that adding caffeinated water to the rodents' diets results in big improvements in the animals' performance on short-term memory and thinking tests.
They've also documented that these mice on caffeine 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. Arendash says in these studies, the dose of caffeine is critical to the protective effect.
Dr. ARENDASH: The human equivalent of two cups of coffee does not have benefits in our Alzheimer's mice. Five does. So you can see that many of us are below that threshold level that confers what we believe is protective benefits.
AUBREY: So now we know why Arendash is committed to his five cups. But can we really translate studies in mice into reliable advice for humans? Not so easily, says researcher Joan Lindsay of the University of Ottawa. Animal research is tricky.
Dr. JOAN LINDSAY (University of Ottawa): It's always a good starting point, but we never know how well it's going to hold up with humans.
AUBREY: Human physiology is 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.
And it takes some real efforts to do a reliable test of the memory of mice. Here's what Arendash has come up with. He puts mice in little swimming pools with lots of alleys and dead-ends to see how quickly they can find and remember hidden escape platforms.
Dr. ARENDASH: The first thing that is lost in Alzheimer's is short-term memory, the memory for what happened a few seconds, a few minutes ago. And that is what this task is focusing on.
AUBREY: Now, there may not be so much interest in Arendash's mice studies if scientists hadn't also begun to gather some evidence from observing coffee drinkers that a steady caffeine habit is beneficial to people, too.
One recent study comes from the northern European country of Finland, where researchers followed about 1,400 coffee drinkers for more than two decades. Neurobiologist Huntington Potter of the University of South Florida explains the Finnish researchers found one group seemed to benefit the most: those who'd been drinking three to five cups of coffee a day throughout middle age.
Dr. HUNTINGTON POTTER (Neurobiologist, University of South Florida): They had about a 65-to-70 percent reduced risk of developing Alzheimer's disease in their 70s.
AUBREY: Potter says the effect held up even when researchers controlled for things such as cardiovascular disease, which can influence the risk of dementia. So, in his estimation, it's a good study. But does it prove that lots of coffee drinking prevents Alzheimer's? Not by a long shot, says Harvard researcher Reisa Sperling. Finnish coffee drinkers might have other habits in common that could explain the protective effect. Say, for example...
Dr. REISA SPERLING (Brigham and Woman's Hospital, Harvard University): People who are very active in mid-life are much more likely to be drinking coffee than couch potatoes. And so I would hesitate to say that that's, you know, epidemiologic evidence that coffee prevents Alzheimer's disease.
AUBREY: Sperling says Alzheimer's is an incredibly complicated disease. Exercise and good nutrition do seem to be protective, but one's risk is largely determined by genes. No one thing - even coffee drinking - can erase that risk. If future research brings stronger evidence that caffeine may modify the risk by some small percentage, coffee lovers will have one more reason to drink away. Just make sure those five cups don't keep you up all night, because sleep is important to your health, too.
Allison Aubrey, NPR News.