Exercise and a diet fortified with vitamins, fruits and vegetables helped older dogs learn new tricks and kept them spry in an experiment that scientists said could teach humans a thing or two.

Beagles given either the fortified diet, regular exercise or both did much better in learning new tricks than dogs fed regular chow and allowed to lie around more, the researchers reported on Tuesday.

Dogs are similar to humans in their dietary needs and the way they digest food, so the findings have implication for people, said Molly Wagster of the National Institute on Aging, which funded the study.

Dogs also can develop memory and learning problems as they age in much the same way people do.

"This research brings a note of optimism that there are things that we can do that may significantly improve our cognitive health," Wagster said in a statement.

"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," added Elizabeth Head of the University of California Irvine, who worked on the study.

"We're excited about these findings because the interventions themselves are relatively simple and might be easily translated into clinical practice for people."

For the study, Head, William Milgram of the University of Toronto in Canada and colleagues studied 48 older beagles over two years.

Writing in the journal Neurobiology of Aging, they said they divided the dogs into four groups that got either standard care; a diet supplemented with tomatoes, carrot granules, citrus pulp, spinach flakes and supplements; standard care plus extra exercise and play; or the special diet and the special play and exercise regime.

A second set of 17 dogs aged 1 to 3 got either a standard or fortified diet.

Tests included having to find a hidden treat. The older dogs clearly benefited from the special diet and the special exercise program, the researchers said.

All 12 of the older beagles that got a supplemented diet and exercise could solve a difficult problem, compared to eight of 10 dogs that got the enriched diet alone and two of eight dogs that got no special treatment.

Last week the U.S. government issued new guidelines that encouraged Americans to eat more fruits and vegetables and to exercise for at least an hour a day to improve their health.