1. Less Stress, Better Blood Pressure Having sex could lower your stress and your blood pressure. That finding comes from a Scottish study of 24 women and 22 men who kept records of their sexual activity. The researchers put them in stressful situations -- such as speaking in public and doing math out loud -- and checked their blood pressure. People who'd had sex responded better to stress than those who engaged in other sexual behaviors or abstained. 2. Sex Boosts Immunity Having sex once or twice a week has been linked with higher levels of an antibody called immunoglobulin A, or IgA, which can protect you from getting colds and other infections. A Wilkes University study had 112 college students keep records of how often they had sex and also provide saliva samples for the study. Those who had sex once or twice a week had higher levels of IgA than other students. 3. Sex Burns Calories Thirty minutes of sex burns 85 calories or more. It may not sound like much, but it adds up: Forty-two half-hour sessions will burn 3,570 calories, more than enough to lose a pound. Doubling up, you could drop that pound in 21 hour-long sessions. 4. Sex Improves Heart Health A 20-year-long British study shows that men who had sex two or more times a week were half as likely to have a fatal heart attack than men who had sex less than once a month. And although some older folks may worry that sex could cause a stroke, the study found no link between how often men had sex and how likely they were to have a stroke. 5. Better Self-Esteem University of Texas researchers found that boosting self-esteem was one of 237 reasons people have sex. That finding makes sense to sex, marriage, and family therapist Gina Ogden. She also says that those who already have self-esteem say they sometimes have sex to feel even better. Of course, you don't have to have lots of sex to feel good about yourself. Your self-esteem is all about you -- not someone else. But if you're already feeling good about yourself, a great sex life may help you feel even better. 6. Deeper Intimacy Having sex and orgasms boosts levels of the hormone oxytocin, the so-called love hormone, which helps people bond and build trust. In a study of 59 women, researchers checked their oxytocin levels before and after the women hugged their partners. The women had higher oxytocin levels if they had more of that physical contact with their partner. Higher oxytocin levels have also been linked with a feeling of generosity. So snuggle up -- it might help you feel more generous toward your partner. 7. Sex May Turn Down Pain Oxytocin also boosts your body's painkillers, called endorphins. Headache, arthritis pain, or PMS symptoms may improve after sex. In one study, 48 people inhaled oxytocin vapor and then had their fingers pricked.The oxytocin increased their pain threshold by more than half, meaning they sensed pain at a higher threshold or were more tolerant of pain. 8. More Ejaculations May Make Prostate Cancer Less Likely Research shows that frequent ejaculations, especially in 20-something men, may lower the risk of getting prostate cancer later in life. A study published in the Journal of the American Medical Association found that men who had 21 or more ejaculations a month were less likely to get prostate cancer than those who had four to seven ejaculations per month. The study doesn't prove that ejaculations were the only factor that mattered. Many things affect a person's odds of developing cancer. But when the researchers took that into consideration, the findings still held. 9. Stronger Pelvic Floor Muscles For women, doing pelvic floor muscle exercises called Kegels may mean more pleasure -- and, as a perk, less chance of incontinence later in life. To do a basic Kegel exercise, tighten the muscles of your pelvic floor as if you're trying to stop the flow of urine. Count to three, then release. 10. Better Sleep The oxytocin released during orgasm also helps sleep, research shows. Getting enough sleep has also been linked with a host of other health benefits, such as a healthy weight and better blood pressure. That's something to think about, especially if you've been wondering why your guy can be active one minute and snoring the next.