A flurry of small studies suggest that sex is as good for your health as vitamin D and broccoli. It not only relieves stress, improves sleep and burns calories, it can also reduce pain, ease depression, strengthen blood vessels, boost the immune system and lower the risk of prostate and breast cancer.
Stress relief: The rush of hormones boosts mood, fosters feelings of closeness and helps manage stress for days.
Weight: Sex burns about five calories per minute, meaning it would take roughly 12 hours to lose a pound.
Longevity: More sex means longer lives for men; women live longer when they are sexually satisfied.
More research is needed to evaluate all these claims. “If I told you we have randomized double-blind placebo-controlled multi-center trials on these questions, there is no such a thing,” says Irwin Goldstein, a urologist and editor in chief of the Journal of Sexual Medicine. The biggest obstacle is lack of funding, he says. “If ‘sex’ is in your grant proposal, it’s very hard to get it approved.”
Still, a look at what researchers do know about the physiology of sex shows that at least a few health benefits may come along with that roll in the hay.
Some benefits of sex—beyond producing a baby, that is—are obvious even without scientific evidence. “When you have good sex, there’s a relaxation response and a satiation response…you lie there and life is great,” says Dr. Goldstein, who is also the director of sexual medicine at Alvarado Hospital in San Diego, Calif.
Much of that is due to chemistry—the rush of hormones and neurotransmitters that rise and fall during sexual activity. Arousal boosts dopamine, which activates the brain’s centers of craving and reward “just like chocolate and winning at gambling,” says Erick Janssen, a senior scientist at the Kinsey Institute at Indiana University.
Sex also increases oxytocin, known as the “cuddle hormone,” which promotes bonding, reduces fear and stimulates endorphins, the body’s natural painkillers, which is why sex can bring temporary relief from back pain, migraines and other body aches.
Dopamine levels plummet after orgasm, and levels of prolactin rise, bringing on feelings of satisfaction and sleepiness, particularly in men. “That’s the nice, relaxed feeling afterwards,” says Stuart Brody, a psychologist at the University of the West of Scotland who has conducted numerous studies on sex and health. Of course, timing isn’t always perfect. In a 2006 survey of 10,000 British men, 48% admitted to having fallen asleep during sex.
All together, this chemical cascade has a lasting effect that helps people handle stress, which Dr. Brody showed in a study in the journal Biological Psychology in 2005. He had 24 women and 22 men keep diaries of their sexual activities for two weeks, then took their blood pressure while they were told to give an impromptu speech to a hostile audience and do rapid math calculations in their heads. Those who had had traditional sexual intercourse during the fortnight had smaller blood pressure spikes and recovered more quickly than those who engaged in other forms of sex or none at all.
Sex is also touted as good exercise—but the effect is actually modest. Although couples obviously differ, sex generally burns an estimated five calories per minute, or roughly 50 to 150 calories total. Calculated another way, orgasm uses 3 to 4 METs (metabolic equivalent tasks, a measure of physical intensity)—the equivalent of light housekeeping.
Sex does increase heart rate and blood pressure—as high as 125 beats per minute and to 160 peak systolic rate—about as much as walking up a flight or two of stairs. And several studies suggest that having it regularly can protect against cardiovascular problems. One British study found that men who reported having three or more orgasms per week experienced 50% fewer heart attacks than those who engaged less frequently—perhaps because orgasm triggers the release of the hormone DHEA (dehydroepiandrosterone), which helps with circulation and arterial dilation.
On the other hand, erectile dysfunction can be an early indicator of cardiovascular problems—and when drugs such as Viagra first came on the market, some cardiologists feared sex could be dangerous to men with underlying heart problems. In general, such fears have proven unfounded. Cases of sudden death during sex are actually very rare, according to studies in Germany, Japan and Korea. But they are more likely to occur during extramarital sex.
Frequent sex may benefit men’s health another way: by boosting testosterone, which in turn is linked to stronger muscles, more energy and better cognition. (Sex’s effect on testosterone was shown in a now-famous article in Nature in 1970. A man stranded on a remote island with no women saw his beard stop growing. Then it resumed when he returned to civilization and sex again.)
Sex also improves women’s moods—although how it does is controversial. One 2002 study of 293 college women at the State University of New York in Albany found that those who engaged in unprotected sex were less likely to be depressed than those whose partners use condoms or who don’t have sex at all. The researchers noted that semen contains testosterone, estrogen, prolactin and prostaglandins, which can pass through vaginal walls into the bloodstream and elevate mood. But safe-sex groups add that the unintended results of unprotected sex—pregnancy and sexually transmitted diseases—can put quite a damper on mood.
Some of the most intriguing findings suggest that frequent sex can lower the risk of some types of cancer. A 2004 study of 29,000 male health professionals in the Journal of the American Medical Association found that those who reported having the most frequent ejaculations—21 or more a month—had a much lower risk of prostate cancer than those reporting four to seven per month.
“Emptying the tank every once in awhile is probably good for the prostate,” Dr. Goldstein says. Still, the authors noted that the data “may have contained some inaccuracy” since it asked men, some in their 80s, to recall how often they ejaculated each month four decades earlier.
Similarly, a 1989 study in France found that women who had sex infrequently or not at all had three times the risk of breast cancer compared to those who had sex more frequently—but the possible biological mechanism is less clear.
Several studies also suggest that having sex extends life in general. A study in the British Medical Journal found that men who had sex less than once per month were twice as likely to die in the next 10 years than those who had sex once per week. A 25-year study of 270 men and women aged 60 to 96 conducted at Duke University found that the more men had sex, the longer they lived. Women who said they enjoyed their sex lives lived seven to eight years longer than those who were indifferent. But factors such as intelligence, health and activities also played a role in living longer, too.
So should people ramp up their sexual activity to be healthier?
Not necessarily. “The ‘more is better’ prescription is too simplistic,” says the Kinsey Institute’s Dr. Janssen. “What we’ve learned from all our years of research is that what’s important is the satisfaction and the meaning we attach to sex.” In short, “if you’re having sex in a frequency and in a way that is compatible with who you are, then that’s healthy.”
Write to Melinda Beck at HealthJournal@wsj.com