Most of us concerned about our health have heard the recommendation to walk 10,000 steps a day. But is 10,000 really the magic number? Or, like the adage to drink 8 glasses of water daily, is the science not actually that precise?

It turns out that the 10,000 steps a day figure was first catapulted into public awareness by a Japanese firm promoting pedometer sales. The advice migrated across the ocean to the U.S., where it has become so widely accepted that it is even used as a benchmark in many fitness trackers.

Recently, however, Dr. I-Min Lee of Harvard’s Brigham and Women’s Hospital set about to establish a more exact minimum number of steps that are necessary to maintain good health and live a long life. Dr. Lee studied the activity levels of about 17,000 older women whose average age was 72. All wore clip-on fitness trackers to measure their steps as they went about their day-to-day activities. It turns out that women who took about 4,000 steps per day got a boost in longevity, compared with women who took fewer steps.

The relationship between exercise and health benefits is well-established. Regular physical activity protects against hypertension, stroke, heart attacks, circulatory problems and other cardiovascular disease; improves respiration and pulmonary function; and even protects against cancers (e.g., prostate, lung, colorectal for men, and breast, lung, and colorectal for women).

Other beneficial effects of exercise include improved lipid profile, prevention of type 2 diabetes, improved bone-mineral metabolism and body composition—and, of course, stress reduction. That’s because exercise decreases the stress hormones, such as cortisol, and increases production of endorphins, the body’s “feel good” chemicals. It also builds muscle, which retains far more water than fat. Finally, exercise builds mental strength, making you feel more capable of tackling life’s other challenges.

Perhaps the most powerful statistic regarding the benefits of exercise is this: It has been shown to reduce mortality from all causes by as much as 40%.  And, there is a clear dose-response relationship between exercise and reduced mortality. This means that a larger volume of physical activity is associate with a lower all-cause mortality, in both men and women, and in younger and older subjects.

Bottom line: exercise is good for you! A little is good; more is better! And to increase the odds that you’ll stick with it, make it something you enjoy–whether that means walking, running, swimming, gardening, dancing, or a little bit of all of the above. And don’t beat yourself up if you don’t achieve 10,000 steps today. Perhaps you will achieve 20,000 tomorrow!