* Heart: Lots of studies have looked at whether DHEA, a hormone released into the bloodstream during arousal and orgasm, helps keeps arteries clear and hearts strong. A 2001 study of 1,700 middle-age Massachusetts men found that those with the lowest levels of DHEA were about 60% more likely to develop heart disease than those with the highest. Orgasms aren't the only way to get this hormone, though; your body produces some even without sexual stimulation.
* Breast: Oxytocin -- a hormone released during sexual arousal, orgasm and breast-feeding -- has been linked to reduced risk of breast cancer. And not just for women: A small, 2000 study of 23 Greek men found that those with breast cancer tended to have a history of fewer orgasms than did healthy men in the control group. One 1995 study speculated that the hormone helps flush out carcinogens from breast fluid.
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* Prostate: Two large studies, reported in 2003 and 2004, found that middle-aged men who had (or at least remember having) at least four orgasms a week throughout their 20s, 30s and 40s had a reduced risk of prostate cancer by as much as one-third. Some researchers speculate that ejaculations may clear the prostate of carcinogens.
* Physical comfort: In laboratory studies, women are able to tolerate more pain when a vibrator is applied to their vaginas. When that stimulation leads to orgasm, their pain threshold doubles. And one small study found that orgasms provided some relief for women suffering from migraines.
* General health: A 10-year study of Welsh men in 1997 found that those who had two or more orgasms per week had half the risk of dying compared with their less sexually active neighbors. Public service messages might be helpful in encouraging people to have more orgasms, the researchers speculated, perhaps akin to the five-a-day vegetable campaign -- although, they wrote, the recommended number of servings might need to be "adjusted."
And finally, a caveat: Researchers haven't done clinical trials in which they assign people into a lots-of-orgasms group and a once-in-a-blue-moon group. Thus it's difficult to rule out other underlying causes. Perhaps the true health boost comes from being in loving, committed relationships or enjoying overall rollicking health.
Self-experiment at your own risk.