By Devi Nampiaparampil, MD, MS (“Doctor Devi”)

Heart disease is the number one killer of both men and women across the world. Although the medical focus has been on diet and exercise, research suggests we might have another—potentially more powerful—intervention: a loving relationship.

The early research concentrated on the health effects of marriage. In 2007, the Department of Health and Human Services found that married people live longer and have fewer medical appointments than unmarried folks. Japanese scientists determined that never-married men were three times more likely to die of heart disease than married men.

That could mean one of two things. Perhaps being married confers a health benefit. Or, maybe healthy people are more likely to get married. Scientists tried to tease out the answer by studying more than 3,600 people over a 10-year period. After accounting for cardiovascular risk factors such as age, body fat, smoking, blood pressure, diabetes and cholesterol levels, married men had a 46 percent lower rate of death than unmarried men.

A report from the National Institute of Medicine also found that having intimate relationships helps you live longer. Why would marriage affect your health? The physiologic changes that occur in your body when you’re in love might improve your health habits, lower your stress hormone levels and lower your blood pressure. One study found that the more educated a man’s wife was, the lower his risk for medical problems such as coronary artery disease, high blood pressure, high cholesterol, smoking and obesity. A 2009 study showed that men married to more educated women also had a lower death rate than men married to less educated women. It’s possible more educated women might have more knowledge about health. Therefore, they might promote healthier habits in their spouses.

Regardless of education level, being in love often changes how you act. If you feel like you have meaning and purpose in your life, you might take better care of yourself for your partner. You might take fewer risks. Research suggests that people in love drink less, exercise more, and floss more.

Scientists are discovering that the benefit may not be behavioral alone. There are physiologic underpinnings to why relationships might improve your heart health. When you feel stressed, your body releases stress hormones to help you adapt. This is called the “fight or flight” response. When you’re really anxious, these hormones cause your heart to race and your blood pressure to go up.

When you water delicate indoor plants, you probably use a spray bottle that creates a light mist. Those water droplets are propelled out of the bottle—but at a very low pressure—so they land gently on the leaves and roots. If you watered your house plants with a garden hose, you would damage them. The pressure generated inside the hose would be too high for the plant to withstand. The same is true in the body. When your blood pressure rises to high levels, the blood doesn’t nourish your brain and heart in the same way. Instead, it practically assaults those organs causing damage.

There’s evidence that being in love lowers your body’s stress hormone levels. Without those stress hormones there to elevate your blood pressure, it comes down. Your heart and other organs get some relief. And that can translate to living longer.

The body does this through a hormone called oxytocin. Oxytocin was first studied because of its role in mother-child bonding. Around the time of labor and delivery, its levels in the mother increase. It also increases during breastfeeding. Scientists later discovered that both men and women release the hormone. Activities like hugging, holding hands and cuddling release oxytocin in both sexes. The hormone promotes bonding, attachment, and feelings of contentment.

Researchers dubbed oxytocin the ‘anti-stress’ hormone because it lowers stress hormone levels in the body, thereby reducing blood pressure. This could protect your heart.

Oxytocin works alongside the body’s natural reward chemical, dopamine. Every time your body does what your brain wants it to, the brain gives it a treat—dopamine. If your body fails, it doesn’t get that dopamine. This is why people feel happy when they do something well and they feel disappointed when they do something poorly. When you’re in love, your brain gives you more dopamine. As a result, you feel more pleasure. That’s why falling in love often involves a mixture of pleasure and attachment.

What happens if you’re not in love? Researchers looked at data from approximately 300,000 people and found that being socially connected—being part of a community—could also add years to your life.

And owning a pet, particularly a dog, can reduce your risk of heart disease. This could be related to exercise habits. A study of more than 5,000 people showed that dog-owners walk much more than those who don’t have dogs. Dog owners are also less obese. Other studies suggest having a pet—who showers you with unconditional love—can reduce your stress hormones and improve your blood pressure.

Bottom line: this Valentine’s Day, consider showering someone—a romantic partner, a friend, a colleague, or a pet with love. It could help you live longer.