(CNN) "I know a man who gave up smoking, drinking, sex and rich food. He was healthy right up to the day he killed himself."
This old wisecrack is credited to American late-night talk show host and comedian Johnny Carson. Sorry, Johnny, it may be funny, but you've got it wrong. Although giving up unhealthy habits like smoking, drinking and rich food will certainly improve your health, giving up sex will not.
In fact, when you're in a healthy relationship, sex is one of the best things you can do for yourself. Here are 10 reasons why.
If you're stressed, sex may be the last thing on your mind. But if you can get in the mood, sex is a great stress-reliever. The act of sex floods your brain with all sorts of feel-good chemicals while reducing the stress hormone cortisol.
Dopamine, which impacts the brain's pleasure and reward centers; endorphins, which can reduce pain and stress; and oxytocin, also known as the cuddle hormone, are all released during sex, with higher levels after orgasm.
Oxytocin promotes feelings of well-being and happiness. And you don't have to boink like bunnies to feel that way.
A study of 30,000 American men and women between 1989 and 2012 found that having sex at least once a week in a committed relationship was enough to make people happy.
It's more than the coital act that brings benefits. Studies of older adults found that holding hands, hugging, kissing and mutual stroking also contribute to a greater quality of life.
Getting it on can ward off depression, too. Studies show that men and women who have intercourse with their partners have greater satisfaction with their mental health. (Unfortunately, the benefits didn't extend to masturbation.)
But the boost doesn't appear to work for casual sex or hookups. One study of nearly 7,500 US college students across 14 public universities found that those who had more hookups had lower levels of happiness and self-esteem, and higher levels of depression and anxiety.
In contrast to the notion that men are more likely to be OK with casual sex, the researchers found no differences between the sexes.
Prolactin, a hormone that relaxes you, is also released after an orgasm. The combination of prolactin and all the rest of the "feel-good" hormones are why most people sleep better after sex.
To get the highest amount of prolactin, science suggests having an orgasm with a partner if possible. Research shows that the level of prolactin in both men and women after intercourse can be "400% greater than that following masturbation."
Unfortunately, sleep deprivation -- which affects a third of Americans -- can also impact sexual satisfaction. A study of nearly 10,000 women ages 50 to 79 found that those who got fewer than seven to eight hours of sleep a night were less likely to be sexually active. The older the woman, the more likely she was to report less sex when sleep-deprived.
Sleep disorders can play a role. For example, men and women with obstructive sleep apnea, characterized by loud snoring and periods of breathing cessation, report a less active sex life.
Men are especially hard-hit. To produce testosterone, men need a good period of restful, uninterrupted sleep. Without that, they could have lower levels of testosterone and suffer erectile dysfunction.
What happens when sleep is improved? Good news for both sexes: Libido goes up.
According to a 2015 study, women who got a good night's sleep were more likely to experience sexual desire the next day. In fact, a one-hour increase in sleep duration correlated to a 14% increase in the odds that a woman would engage in sex with her partner.
And researchers at Walter Reed Army Hospital found that using a CPAP machine, a breathing apparatus used to correct sleep apnea, improved sexual function and satisfaction for all men in their study but was especially helpful to those with erectile dysfunction.
Read: Do you get enough sleep?
Having regular sex may also help you fight off disease.
Researchers at Pennsylvania's Wilkes University asked US college students how often they had sex each week and then compared the levels of immunoglobulin A, an antibody that functions as the body's first line of defense, in their saliva.
Students who had sex once or twice a week had the highest levels of immunoglobulin A: 30% higher than those who had no sex, but also those who had sex three or more times a week. In addition, students who were in longer-term, satisfying relationships had the highest levels of the antibody.
That makes sense when you consider research on social support and the immune system. A study of 276 healthy volunteers at the University of Pittsburgh found that those with the most diverse social networks, including not just lovers but family, friends and organizations, were the least likely to catch colds.
Good news for men: Frequent ejaculation appears to be linked to a lower risk for prostate cancer.
A 2004 study published in the British Medical Journal studied the sex life of over 50,000 American males between the ages of 40 and 75. Men reporting 21 or more ejaculations a month were less likely to get prostate cancer than men who ejaculated four to seven times a month. A follow-up study published in 2016 showed the same results.
Men who make love at least two times a week are 45% less likely to have heart disease than men who have sex only once a month or less, according to a study by the New England Research Institute.
The 17-year study, which began in 1987, tracked the sex lives of over 1,000 men age 40 to 70; the researchers eliminated other risk factors from the results, such as age, weight, cholesterol and blood pressure.
Women also reap the heart-healthy benefits of sex. A 2016 study found that women who said they had frequent, extremely satisfying sex had a lower risk of hypertension, a common precursor to heart disease.
"Good sexual quality may protect older women from cardiovascular risk in later life," said study author Hui Liu, an associate professor of sociology at Michigan State University.
That makes sense, said sex and relationship educator Laura Berman, because of the way women view their sexual relationships.
"It's not so much the number of orgasms or how vigorous the sexual experience that predicts a woman's sexual satisfaction," Berman said. "It's how close she feels to the person she is having sex with, through kissing and cuddling as well as orgasms. That is the key to her emotional and physical well-being, which benefits her health and her heart and everything else."
Want more affection in your life? Have more sex with your partner.
A series of four studies of committed couples in the United States and Switzerland found that having sex created more affection, not only in the moments after sexual intimacy but hours later, even in couples with children or those married long past the "honeymoon period."
Moreover, for couples who felt more affection after sex, the effects were still evident six months later.
"The more overall sex they had, the more affection; the less sex they had, the less positive affection," said clinical psychologist Anik Debrot of the University of Lausanne in Switzerland, who led the study.
And the sex didn't have to be intercourse for there to be positive effects, Debrot said. "Moments that were experienced as erotic or sexually arousing were just as predictive of positive emotions."
CNN contributor Ian Kerner, a psychotherapist who specializes in sex and couples therapy, agrees. When couples keep the sexual dimension of their relationship alive and intact, "it leads to an overall warming up of the relationship, which includes more touch and non-sexual affection as well as higher level of regard towards their partner," he said.
If you're looking for a good reason to energize your sex life as you age, here it is.
Studies show that keeping your sex life active into old age protects and even improves your brain's executive functioning and recall. Analyzing data from the English Longitudinal Study of Ageing, British researchers found that sexually active men between the ages 50 and 89 had increased cognitive function, as measured by number sequencing and word recall, even after adjusting for quality of life, loneliness, depression and physical activity.
Women had the same benefit from sex for memory but not number sequencing.
Both men and women who were more sexually active did better on the tests than those who had less sex.
In a follow-up study, the researchers found that having sex at least once a week was highly predictive of improved cognitive functioning, especially verbal fluency.
Studies have found that sexual activity can reduce menstrual cramps, chronic back and leg pain, even migraines.
A 2013 survey of 1,000 German headache sufferers found that 30% of those with cluster headaches and 60% of those with migraines reported partial or total relief of their pain if they had sex during an episode.
Orgasm researcher Barry Komisaruk of Rutgers University points to research that states "the sensory input produced by vaginal stimulation produces a powerful analgesic effect" and that he says does not interfere with tactile sensitivity.
In a study Komisaruk co-authored with Rutgers sex researcher Beverly Whipple, who coined the term "G-spot," they found that the pressure of pleasurable vaginal stimulation increased pain tolerance by 40%. When the women came to orgasm, their pain tolerance increased by nearly 75%.
Scientists give the credit to hormones released during sex, like endorphins, which block pain and stress, and oxytocin, the hormone that helps mothers and babies bond and which has pain-relieving properties.
Can sex be a form of exercise? Yes, sort of, if you are young and healthy and spend at least 30 minutes doing it.
A study of 20 young healthy couples found that they burned an average of 85 calories for each half-hour romp in bed. Men burned more than women, at about 100 calories versus 69.
"By comparison," the study authors write, "the level of intensity that is exerted from sexual activity could be higher to that of walking at 4.8 km/h but lower to that of jogging at 8 km/h."
Still, a man would burn about the same amount of calories in a half-hour of cooking, bartending or driving a truck, while women get the same result from desk work and sitting in meetings.
But which is more fun? Plus, experts point to the other exercise benefits from sex: the stretching of muscles and tendons, the flexing of joints and the increase of respiration, heart rate and blood pressure that in a healthy man or woman can energize the body.