It is never too late to eat well and exercise every day, according to a quartet of new studies that found healthy lifestyles can produce dramatic benefits for the body and mind, even among the elderly.

Although an abundance of research has demonstrated that a good diet and regular physical activity are potent promoters of health, the four studies released yesterday found that the effects extend into old age, sharply reducing the risk not only of heart disease and cancer, but even of dementia.

"A lot of times older people get the idea that, 'What's done is done. It's too late for me now,' " said Meir J. Stampfer of the Harvard School of Public Health, who co-wrote an editorial accompanying the research in today's Journal of the American Medical Association. "This says, 'It's not too late to have a big influence.' "

One of the studies found that elderly people who ate a healthful diet, exercised regularly, drank alcohol moderately and avoided smoking slashed by more than half their risk of dying from any cause during the study period, while another found that the same type of diet improved blood vessel function and reduced inflammation. The two other studies produced the strongest evidence yet that simply walking every day goes a long way toward keeping the mind sharp and warding off dementia, including Alzheimer's disease.

Taken together, the new studies provide some of the most definitive evidence to date that relatively simple, inexpensive lifestyle changes can dramatically improve the health and well-being of the elderly, experts said.

"This package really provides a lot more data supporting the whole concept that lifestyle matters," Stampfer said.

The findings are particularly important because of the rapidly increasing number of Americans who are elderly, a driving force behind skyrocketing health care costs in the United States.

"The most important message for the public is, the combination of all these factors can have an enormous impact," said Perry Hu, a geriatric medicine expert at the School of Medicine at the University of California at Los Angeles.

In the first study, the most comprehensive attempt to date to assess the health effects of various lifestyle factors among the elderly, researchers followed 1,507 healthy men and 832 women ages 70 to 90 in 11 European countries for 10 years.

Those who led the most healthy lifestyles were more than 50 percent less likely to die from any cause. A healthy lifestyle consisted of a "Mediterranean diet," which is rich in grains, olive oil, vegetables, fruits and fish, and low in meat and dairy products. It also included about 30 minutes of moderate activity a day, such as walking; consuming about two or three alcoholic drinks a day; and not smoking.

Each of those lifestyle choices alone had a dramatic effect on health, individually reducing by more than one-fifth to more than one-third the risk of dying from any cause, the researchers found. Overall, 60 percent of all deaths, 64 percent of deaths from heart disease, 61 percent of deaths from cardiovascular disease and 60 percent of deaths from cancer were associated with a failing to live that kind of life, the study found.

"This says, 'Even if you are older, you have to pay attention to your diet and look at your alcohol consumption, physical activity and smoking,' " said Kim T.B. Knoops of the Wageningen University in the Netherlands, who led the study.

The second Mediterranean diet study found that it improved blood vessel function and reduced inflammation in people suffering from an increasingly common condition known as the metabolic syndrome, which boosts the risk for heart disease and diabetes.

The two remaining studies were among the first to follow large numbers of older men and women over time to determine whether the amount of physical activity they did, including walking, affected the health of their minds.

In the first, researchers followed 16,466 women participating in the Nurses' Health Study. The women were in their late fifties and early sixties when the study began.

When the women were in their seventies and early eighties, those who reported the most physical activity, including walking, scored significantly higher on tests measuring learning, memory and attention than those who reported the least, and the more active they were the better their cognitive functioning, the researchers found.

"Our data do support the contention that being active does protect your brain," said Jennifer Weuve of the Harvard School of Public Health, who led the study.

In the second, researchers followed 2,257 men ages 71 to 93 participating in the Honolulu-Asia aging study from 1991 to 1999, specifically examining the relationship between daily walking and the risk for dementia. Those who walked the least -- less than a quarter-mile a day -- were about twice as likely to develop dementia, including Alzheimer's, than those who walked the most, more than two miles a day.

Although neither study examined how physical activity might protect mental function, other research suggests it may improve blood flow to the brain or perhaps promote brain cell growth and connections between neurons.

"There is some evidence that physical activity has a direct effect on the brain," said Robert D. Abbott of the University of Virginia in Charlottesville, who led the Honolulu study.