Diet, Exercise, Stimulating Environment Helps Old Dogs Learn
According to conventional wisdom, old dogs and new tricks aren’t
a good match. But a new study of beagles finds that regular physical
activity, mental stimulation, and a diet rich in antioxidants can
help keep aging canine — and perhaps human — brains
in tip-top shape. The research, supported by the National Institute
on Aging (NIA), a part of the National Institutes of Health (NIH),
is among the first to examine the combined effects of these interventions
and suggests that diet and mental exercise may work more effectively
in combination than by themselves.
During the two-year longitudinal study, William Milgram, Ph.D.,
of the University of Toronto, Elizabeth Head, Ph.D., and Carl Cotman,
Ph.D., of the University of California, Irvine and their colleagues
found older beagles performed better on cognitive tests and were
more likely to learn new tasks when they were fed a diet fortified
with plenty of fruits, vegetables and vitamins, were exercised
at least twice weekly, and were given the opportunity to play with
other dogs and a variety of stimulating toys. The study* is
reported in the January 2005 Neurobiology of Aging.
Dogs are an important model of cognitive aging, and these findings
could have important implications for people. Like humans, dogs
engage in complex cognitive strategies and have a more complicated
brain structure than many other animals. Dogs also process dietary
nutrients in ways similar to humans. And like people, dogs are
susceptible to age-related declines in learning and memory, and
can develop neuropathology similar to Alzheimer’s disease.
“This research brings a note of optimism that there are things that we
can do that may significantly improve our cognitive health,” says Molly
Wagster, Ph.D., program director of the NIA’s Neuropsychology of Aging
Branch. “In this case, more was better. Although each factor alone was capable of improving cognitive function in older animals,
the combination was additive, pointing to a healthy lifestyle
as the most beneficial approach. While we have yet to demonstrate
these benefits in people, research such as this gives us new
ways to think about the aging brain and what we can do to keep
For the study, the researchers divided 48 older beagles (ages
7 to 11) into four groups. One group was fed a regular diet and
received standard care; a second group received standard care
but was fed an antioxidant fortified diet, consisting of standard
dog food supplemented with tomatoes, carrot granules, citrus
pulp, spinach flakes, the equivalent of 800 IUs of vitamin E,
20 milligrams per kilogram of vitamin C, and two mitochondrial
co-factors — lipoic acid and carnitine; the third was fed
a regular diet, but their environment was enriched (regular exercise,
socialization with other dogs, and access to novel toys); the
fourth group received a combination of the antioxidant diet as
well as environmental enrichment. In addition, a set of 17 young
dogs (ages 1 to 3) were divided into two groups, one fed a regular
diet and the other fed the antioxidant fortified diet.
The fruits and vegetables added to the antioxidant fortified
diet was the equivalent of increasing intake from 3 servings
to 5 or 6 servings daily. Previous research suggests that antioxidants
might reduce free radical damage to neurons in the brain, which
scientists believe is involved in age-associated learning and
memory problems. Mitochondrial co-factors may help neurons function
more efficiently, slash free radical production and lead to improvements
in brain function. Other studies suggest that stimulating environments
improve learning ability, induce beneficial changes in cellular
structure, may help the brain grow new neurons, and increase
the resistance of neurons to injury.
As the study progressed, researchers tested the dogs with a series
of increasingly difficult learning problems, including a task
in which the animals needed to learn whether a treat was hidden
under a black or white block (black/white discrimination). Later,
the treat was hidden under the opposite block so the dogs had
to relearn the task (reversal learning).
Overall, older dogs in the combined intervention group did the
best on these learning tasks, outperforming dogs in the control
group (standard diet, standard care) as well as those that
received either the antioxidant diet or environmental enrichment.
However, older beagles that received at least one of these interventions
also did better than the control group. For instance, all 12
of the older beagles in the combined intervention group were
able to solve the reversal learning problem. In comparison, 8
of the 12 dogs that ate the antioxidant diet without environmental
enrichment and 8 of the 10 that received environmental enrichment
without the antioxidant diet solved the problem. Only two of
the eight older dogs in the control group were able to do this
task. Dietary intervention in the younger canines had no effect.
“The combination of an antioxidant diet and lots of cognitive
stimulation—which was almost the equivalent of going to
school every day—really did improve brain function in these
animals,” says Dr. Head. “We’re excited about
these findings because the interventions themselves are relatively
simple and might be easily translated into clinical practice
The NIA leads the Federal research effort on aging in general
and on aging and memory, including Alzheimer's disease. For more
information on these topics, the public and media are invited
to visit the NIA's websites. Information on memory and Alzheimer's
disease may be viewed at www.alzheimers.org, the NIA's Alzheimer's
Disease Education and Referral (ADEAR) Center website. The general
public also may call the ADEAR Center toll free at 1-800-438-4380.
General information on health and aging may be viewed at www.nia.nih.gov. Publications may be ordered online at www.niapublications.org or by calling the NIA Information Center toll free at 1-800-222-2225.
* Milgram, N.W., Head, E., Zicker, S.C., Ikeda-Douglas,
C.J., Murphey, H., Muggenburg, B., Siwak, C., Tapp, D., Cotman, C.W.
Learning ability in aged beagle dogs is preserved by behavioral
enrichment and dietary fortification: a two-year longitudinal
study. Neurobiol Aging, 2005, 26: 77-90.