Web edition: July 22, 2010
CHICAGO Millions of Americans start their day with a cup of coffee and then reach for refills when their energy or attention flags. But new research in rats suggests that for the aging brain, coffee may serve as more than a mere stimulant. It can boost memory and the signaling essential to motor coordination.
But here's the rub: If the same effects hold for humans, downing a morning cup or two just won’t cut it. The new data, presented July 20 at the Institute of Food Technologists annual meeting, showed that among elderly rats, the best results emerged after months of downing the human equivalent of 10 cups per day.
And before you ask: No, that didn’t leave the furry test subjects jittery.
“They weren’t hyper at all,” notes Barbara Shukitt-Hale of the Agriculture Department’s Human Nutrition Research Center on Aging at Tufts University in Boston. “You’d think that with the equivalent of 10 cups per day they would be. But in fact,” the experimental psychologist observes, “you couldn’t tell the difference between a rat that had been getting the equivalent of 15 cups a day [the highest administered dose] and the rat that had none.” For instance, when placed in a pool for a water-maze test, those that had been downing the super doses didn’t swim any faster in their rush to find a safe haven and climb out of the yucky water.
Led by the late James Joseph, this USDA team at Tufts has been investigating the protective effects of certain foods — most notably blueberries — on brain health. They’ve just extended their work to include coffee. Which isn’t all that surprising since a number of studies over the past decade have indicated that coffee consumption can improve accuracy on certain mental tasks.
At an IFT session on coffee’s health benefits, Shukitt-Hale described new data from geriatric rodents. The rats were already 19 months old — analogous to 65- or 70-year-old people — when the study began. For the next two months, treated animals each received a diet that had been laced with high-quality freeze-dried coffee in amounts that were equivalent to between 3 and 15 cups of java daily. Another group of rats ate undoctored chow.
Like people, elderly rodents develop balance problems and tend to exhibit progressively poorer memory. To assess these deficits, the USDA scientists administer a pair of experiments. One requires that rodents maintain their balance as they perch on a slowly turning rod (the rotorod). In a second set of tests, each is placed in a pool of water and left to find — and haul out onto — a hard-to-see platform that is moved from one test session to the next. Each animal was tested twice, 10 minutes apart, in this Morris water maze. The reason for the double testing is to examine whether rodents learn what to look for on their second try.
When elderly rodents had dined on diets containing blueberries, they performed better on both tests than did aged rodents getting plain chow. At IFT, Shukitt-Hale reported a similar trend for rats administered coffee-laced meals. The difference: It took about 10 cups of coffee per day to deliver the same benefits achieved with the human dietary equivalent of a half cup to cup of blueberries per day.
In the rotorod tests, for instance, animals in the 10-cups-per-day group successfully balanced on the rotating perch longer than those in any other group. Similarly, during the water maze test, rats in this dose group found the platform about 40 percent faster on their second try than did those getting more or less coffee in their chow.
The only exception: rats in the 3-cups-per-day group. They did about as well on their first try as the 10-cups-per-day group did on their second. And this moderate-coffee group maintained its good performance on the second trials. Rats getting no coffee, the equivalent of 5-cups-per-day or of a whopping 15-cups-day all performed more poorly.
Why remains a puzzle, Shukitt-Hale admits. But they had 15 rats in each treatment group and the trend held for all in a group.
In a followup trial, the Boston scientists will be comparing groups of rats getting various doses of regular coffee to those whose chow contains additions of just caffeine in amounts equivalent to what would be found in that coffee.
Also in the works: A human trial administering coffee to the geriatric set. Here senior citizens will walk on a treadmill (a surrogate for the rotorod) and then researchers will evaluate balance when they get off of the machine. In a second set of tests, seniors will perform the Morris water maze — virtually. Each will do the test on a computer screen instead of within a pool of water.
As to putative mechanisms, there has been a suspicion that the polyphenols — plant antioxidants that often serve as pigments — might help prevent nerve-damaging oxidative stress, which becomes increasingly common with age. However, Shukitt-Hale pointed to some new data by scientists at Kraft Foods (maker of Maxwell House coffee and the source of coffee crystals fed to her rodents) showing that coffee polyphenols may be able to affect brain signaling independent of the chemicals’ antioxidant attributes.
At the IFT meeting, YiFang Chu of Kraft in Glenview, Ill., described data from an Oct. 28, 2009, paper in the Journal of Agricultural and Food Chemistry. It showed that roasting appears to not only increase the availability of coffee’s polyphenols to brain cells (at least to cells growing in a dish), but also the ability of these coffee constituents to protect those cells from oxidative damage. The coffee molecules appear to calm the cells so that they don’t become overstimulated by stess (like oxidation), Shukitt-Hale says. The Kraft team identified the affected proteins that become quieted as ERK and JNK.
What’s interesting, Chu noted at the meeting, is that although green, unroasted beans offer some protection for brain neurons, roasted coffee beans offer a broader, more potent mix of such protective molecules.
Shukitt-Hale, B., Joseph, J. 2010. The effects of coffee on age-related deficits in cognition and motor function. Institute of Food Technologists annual meeting (abstract # 253-03), July 20.
Chu, Y.-F., et al. 2009. Roasted Coffees High in Lipophilic Antioxidants and Chlorogenic Acid Lactones Are More. Journal of Agricultural and Food Chemistry 57(Oct. 28):9801
Chu, Y. 2010. Potential neuroprotective effects of coffee: A mechanistic study comparing green and roasted coffee. zInstitute of Food Technologists annual meeting (abstract # 253-04), July 20.
Raloff, J. 1999. Berry good protection for aging brains. Science News 156(Sept. 18):180.