"Luck is the result of a previous action," wrote Aristotle in his essay Physics in the year 329 B.C. "In this respect, one can also say that happiness and good fortune are the result of previous good actions."

Few would dispute that living to become 100 years old is a particularly appealing sort of good fortune.

Many would be ready to pay a fortune for such privilege, but contemporary medicine still has major difficulties to extend a man's life beyond his eighty-fifth birthday.

In the course of the last three decades, scientific studies on longevity have outgrown the status of fringe curiosities.

Today, trying to figure out how human beings could live longer occupies a central place in medical research.

"Time is a measure of motion and change," observed Aristotle. "Growing old shows the effect of time on living entities."

When researching longevity, the approach taken by the great majority of scientists has been based on the following five steps:

1. Seek out very old people in different countries. 
2. Talk to them and to their families. 
3. Organize the information in four areas, namely, genetic characteristics, environment, lifestyle, and food. 
4. Compare the details in each area. 
5. Identify patterns that explain why those people live much longer than average.

In the late seventies, a population survey in Okinawa, a group of islands located between Japan and Taiwan, discovered an unusually large population segment that had reached an age beyond ninety years old.

The scientific investigation conducted with Okinawan men and women led to the same results as studies carried out in other areas of the world.

No one can modify the genetic characteristics of human beings after their birth, at least for the moment, but researchers agree that we are able to influence the other three factors that determine longevity.

These are some of the ways of turning those factors in our favour:

* ENVIRONMENT: If possible, move to live in an unpolluted area, free of smoke, industrial fallout, and with abundant green areas for relaxation.

* LIFESTYLE: Try to spend a good part of the day outside, cycling, gardening, or simply walking. Live close to friends and see them often. Pursue long-term interests in fields that require continuous learning, skill development, and intellectual concentration. Follow your passions.

* FOOD: Eat moderately and seek to maintain a stable weight. Food affects people in various ways and there is no universal formula for youth. In general, it seems that legumes, fruits, vegetables, nuts, and fish tend to further essential biochemical processes at cellular level. Find out which precise diet works best for you by observing how your metabolism reacts to different foods.

"Virtues are actions that move us in the direction of happiness," defined Aristotle. "In order to find out the right direction to follow, a man should think of the likely effects of his actions."

Let us learn how to live properly by learning from reality. The more we learn, the longer and happier our life will be.