And the brisker the walk, the more the benefit, new research shows.
As for men? The researchers say they most likely could reap the same benefits.
The findings stem from analysis of questionnaires on physical activity completed by more than 72 000 women who participated in the Nurses Health Study. None of the participants had evidence of heart disease or cancer when the study began.
In the eight years that researchers from the Harvard School of Public Health followed the nurses, they documented 258 cases of ischemic stroke, 109 strokes caused by haemorrhage and 40 strokes of unknown cause.
Ischemic strokes, which account for about 80 percent of all strokes, occur when an artery supplying blood to the brain becomes blocked by a blood clot. The clot slows or stops blood flow and causes what's known as a "brain attack."
However, nurses who walked at a normal or moderate pace every day had less risk of having a stroke, and even less risk when they walked vigorously, says researcher Dr Frank Hu, an assistant professor of nutrition at Harvard. Results of the study appear in the Journal of the American Medical Association.
"The role of exercise is not well established in preventing strokes," Hu says.
At least a half-hour of brisk walking and 45 minutes of moderate walking each day produced the protective effect, he says. "Each 3.5-hour-a-week increase in moderate to vigorous activity was associated with a 19 percent reduction in total stroke and a 29 percent reduction in ischemic stroke," Hu says.
Even moderate walking lowers the risk of stroke by "lowering blood pressure and blood cholesterol," Hu says.
"People need to understand that ischemic stroke is similar to heart disease caused by atherosclerosis," he says. Atherosclerosis is the buildup of fatty substances on the walls of blood vessels, resulting in a thickening and hardening of the arteries.
Exercise and walking also reduce "the risk for Type II diabetes, which is a problem in strokes," Hu says. "Exercise causes weight loss and maintenance and is known to improve insulin sensitivity," he says.
Even women who become active later in life have a lower stroke risk than their sedentary counterparts, Hu says.
"Older adults can enjoy the benefit of exercise even if they were sedentary for a long time," he says.
"There is nothing physiologically different in men and women that would change the protective effect," Hu says.