Michael Corleone in “The Godfather” says, “My father taught me many things ... he taught me keep your friends close, but your enemies closer.” Not the formula for a relaxed and happy life. Keep your friends close and your cortisol levels low — now that’s a much better recommendation for a long and healthy future.

A new study in the Journal of Women and Aging looked at friendships and conversation quality in young and older women.

The researchers found that in times of stress, women can kick in a tend-and-befriend response instead of fight-or-flight, and that impulse helps lower their level of stress hormones — cortisol in particular.

That, in turn, reduces the harm that chronically-elevated levels of cortisol can do to the body by pumping up blood glucose, causing body-wide inflammation, reducing immune system function and increasing the risk for cardiovascular disease.

Other studies have shown similar health benefits of social relationships.

• One American-U.K. study from the mid-20th century found that six friend contacts a month were the best way to ease the adverse health effects of stressful life events.

• A 2010 review of research found that having strong social ties increased longevity as much as quitting smoking.

• A three-year Swedish study of more than 13,600 men and women found that having few or no close friends increased the risk of having a first-time heart attack by about 50%.

Especially now, as the world opens up (if you are vaccinated), we hope you take advantage of opportunities to improve your well-being by enjoying the company of others.

Mehmet Oz, M.D. is host of “The Dr. Oz Show,” and Mike Roizen, M.D. is Chief Wellness Officer Emeritus at Cleveland Clinic. To live your healthiest, tune into “The Dr. Oz Show” or visit www.sharecare.com.