We think about sex. We fantasize about sex. We spend an inordinate amount of time and money in the pursuit of sex. We have sex. When you consider AIDS, childbirth, or “honor” killings, our survival and death are often intertwined with sex. Thus, it is worthwhile to spend some time on what scientists have learned about sexuality.
Sex burns calories
Yes, knocking boots counts as exercise—and it sure beats the gym! Depending on how physical you get, sex can strengthen muscle tone, increase your heart rate, and get your whole body working, says Justin Lehmiller, PhD, creator of lecturer in the department of psychology at Purdue University and author of The Psychology of Human Sexuality. And according to a 2013 study in which volunteers wore activity trackers while they did the deed, men burn about 101 calories per session, while women torch an average of 69. “Relatively speaking, that’s not a huge amount,” says Lehmiller. He points out, however, that sex in the study (from foreplay to orgasm) lasted an average of 25 minutes. “If you have sex for a longer period of time, you can have even more of those calorie-burning benefits.”
Sex helps you sleep
After orgasm, the body releases a relaxation hormone called prolactin, says Kristin Mark, PhD, director of the Sexual Health Promotion Lab at the University of Kentucky. “If you’re not feeling particularly tired beforehand, having sex and reaching orgasm may certainly help you nod off a little more quickly than you would have otherwise.”
Sex lowers your blood pressure and stress levels
In a 2005 Scottish study, volunteers were asked to record their sexual activity for two weeks and were then given anxiety-inducing tasks, like public speaking or solving math problems out loud. Those who’d had sex over the study period experienced smaller blood pressure spikes, and recovered from them more quickly, than those who hadn’t. (Only penile-vaginal intercourse seemed to have this effect, not masturbation or other forms of sexual activity.)
The study suggests two important benefit of regular sex, says Mark: Better blood pressure control, and better stress management overall. “Sex not only lowers people’s perceived levels of stress, but it also appears to helps them handle stress more effectively, as well,” she says.
Sex strengthens your heart
Regular sex may benefit the cardiovascular system in other ways. A British study found that men who had sex at least twice a week over a period of 20 years were less likely to have died from heart disease than those who got it on less than once a month. After 10 years, in fact, their risk of sudden death was 50% less than that of the group that had less sex, although that gap lessened over the next decade.
These sorts of findings only show a correlation, not causation, says Mark. “People who have healthy sex lives probably have overall healthy lifestyles.” Even so, she suspects there may be a connection: “Sex helps regulate hormones like estrogen and testosterone,” she says, “which impacts all kinds of systems in the body, including the heart.”
Sex may protect against cancer
Some studies have suggested that men who ejaculate more frequently may have a reduced risk of prostate cancer—although the difference appears to be very small, and others haven’t found a conclusive link.
The benefits may be clearer for breast cancer prevention, however: A French study found that women who had sex at least once a month were less likely to develop breast cancer than those who didn’t. And while the disease is rare in men, those who orgasm less than six times a month appear to be at increased risk of breast cancer compared to those who do so more often, according to a Greek study.
Sex boosts immunity
Getting busy on a weekly basis stimulates the immune system and provides protection from the common cold, according to a Wilkes University study. Researchers gave college students questionnaires about their sex lives, then tested their saliva for levels of immunoglobulin A (IgA), an antibody that helps fight off viruses. They found that the students who had sex once or twice a week had 30% more IgA than those who had sex less frequently. (They also, however, had higher IgA levels than those who had sex three times a week or more, suggesting that in this case, maybe you can get too much of a good thing.)
Sex relieves pain
Women often skip sex because of headaches, or so the cliché goes—but, according to a 2013 German study, going through with it may actually help them feel better. When study volunteers chose to have sex during a headache episode, about 60% of migraine sufferers and 30% of cluster headache sufferers reported partial or total relief.
Endorphins released during orgasm, as well as increased blood flow to the genital area, likely play a role in sex’s pain-relieving power, says Mark. “Pain sometimes has to do with blood flowing to one particular area, like the head, and sex can take some of that pressure off by redirecting the flow.”
Sex may extend your life
Several studies have found connections between a busier sex life and a longer life in general, most notably a Duke University study that took place between 1955 and 1980. Researchers found that for men, frequency of intercourse was related to longer lifespans; while for women, enjoyment of intercourse was the most significant factor.
“We can’t really do cause-and-effect studies, so we don’t know if sex actually helps people live longer, or if healthier people are just having more sex,” says Lehmiller. “But from what we know about the other health benefits of sex, it probably won’t hurt to have more of it!”
Sex strengthens relationships
Oxytocin, also known as the “love hormone,” is released during physical intimacy and skin-to-skin contact—and it can help increase romantic feelings between you and your partner, says Lehmiller.
Want to boost that bond even more? Be sure to cuddle after sex: A University of Toronto study found that couples who were asked to spend extra time together after sex—kissing, talking, and being affectionate—reported higher levels of satisfaction with their sex lives and with their relationships.
Sex is the key to lasting happiness
Physical intimacy can be difficult to maintain as people age, especially if chronic illnesses get in the way. But people couples can especially benefit from staying sexually active, according to a 2014 study from Johns Hopkins University on adults ages 58 to 85: Researchers found that couples who regularly engaged in sexual activity—even as little as once a month—reported greater marital satisfaction and happier relationships than those who hadn’t in a year or more.
Sexual activity didn’t have to mean intercourse, either, or result in orgasm; the study authors say that anything couples do together to stimulate sexual arousal can have a lasting benefit.
Sex makes you smarter
A 2010 Princeton University study found that rats that have more frequent sex show more neuron growth in the hippocampus, a key brain region for learning and memory. “We know there are chemicals released during sex that activate the brain’s rewards center, so it makes sense that this neurogenesis happens in people, as well,” says Lehmiller. “In some ways, sex could potentially make you smarter!”
Sex makes you look younger
Research presented at the 2013 British Psychological Society annual meeting found that study subjects who had frequent sex (at least three times a week for people in their 40s and 50s) look between four and seven years younger than those who had less.
Why? Lead author David Weeks, PhD, suspects the endorphins and feel-good chemicals released during intimacy, plus sex’s beneficial effects on sleep and stress levels. Sex also boosts blood flow and helps regulate hormones, says Mark, which can both have positive effects on skin’s appearance.
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