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Nervous About Alzheimer's? Coffee May Help

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:

More On Coffee Research

Many studies show that coffee has positive health benefits. But a cup a day won't keep the doctor away. That is, nothing as simple as drinking coffee can significantly change the risk of developing most diseases.

For example: While research has suggested coffee might protect against diabetes, being obese or overweight is still the largest risk factor for Type 2 diabetes. And with Alzheimer's, genes are the strongest determinant of developing the disease.

Dr. Donald Hensrud, chair of the Division of Preventive, Occupational and Aerospace Medicine at the Mayo Clinic, recently wrote about coffee research for the clinic's consumer website.

"I think, in general, there's perception that coffee is kind of bad for you," says Hensrud, who drinks two or three cups each morning himself. He says some of his coffee-drinking patients almost sound apologetic when they tell him: "Well, I drink two or three cups of coffee a day."

But as long as they're not having side effects from the coffee, Hensrud tells them it’s probably a good source of antioxidants.

Coffee is studied so often, Hensrud says, because it is commonly consumed. He says the studies' findings probably don't affect coffee drinking habits, but they can help relieve some of the guilt associated with your morning cup.

-- Whitney Blair Wyckoff

"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 Ottawa. "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 2014 NPR. To see more, visit http://www.npr.org/.

Transcript

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. Transcript provided by NPR, Copyright NPR.

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