I came across an interesting article by Alan Farnham in the October 8, 2003 edition of Forbes.com

Fans of abstinence had better be sitting down. “Saving yourself” before the big game, the big business deal, the big hoedown or the big bakeoff may indeed confer some moral benefit. But corporeally it does absolutely zip. There’s no evidence it sharpens your competitive edge. The best that modern science can say for sexual abstinence is that it’s harmless when practiced in moderation. Having regular and enthusiastic sex, by contrast, confers a host of measurable physiological advantages, be you male or female. (This assumes that you are engaging in sex without contracting a sexually transmitted disease.)

In one of the most credible studies correlating overall health with sexual frequency, Queens University in Belfast tracked the mortality of about 1,000 middle-aged men over the course of a decade. The study was designed to compare persons of comparable circumstances, age and health. Its findings, published in 1997 in the British Medical Journal, were that men who reported the highest frequency of orgasm enjoyed a death rate half that of the laggards. Other studies (some rigorous, some less so) purport to show that having sex even a few times a week has an associative or causal relationship with the following:

Improved sense of smell: After sex, production of the hormone prolactin surges. This in turn causes stem cells in the brain to develop new neurons in the brain’s olfactory bulb, its smell center.

Reduced risk of heart disease: In a 2001 follow-on to the Queens University study mentioned above, researchers focused on cardiovascular health. Their finding? That by having sex three or more times a week, men reduced their risk of heart attack or stroke by half. In reporting these results, the co-author of the study, Shah Ebrahim, Ph.D., displayed the well-loved British gift for understatement: “The relationship found between frequency of sexual intercourse and mortality is of considerable public interest.”

Weight loss, overall fitness: Sex, if nothing else, is exercise. A vigorous bout burns some 200 calories–about the same as running 15 minutes on a treadmill or playing a spirited game of squash. The pulse rate, in a person aroused, rises from about 70 beats per minute to 150, the same as that of an athlete putting forth maximum effort. British researchers have determined that the equivalent of six Big Macs can be worked off by having sex three times a week for a year. Muscular contractions during intercourse work the pelvis, thighs, buttocks, arms, neck and thorax. Sex also boosts production of testosterone, which leads to stronger bones and muscles. Men’s Health magazine has gone so far as to call the bed the single greatest piece of exercise equipment ever invented.

Reduced depression: Such was the implication of a 2002 study of 293 women. American psychologist Gordon Gallup reported that sexually active participants whose male partners did not use condoms were less subject to depression than those whose partners did. One theory of causality: Prostoglandin, a hormone found only in semen, may be absorbed in the female genital tract, thus modulating female hormones.

Pain-relief: Immediately before orgasm, levels of the hormone oxytocin surge to five times their normal level. This in turn releases endorphins, which alleviate the pain of everything from headache to arthritis to even migraine. In women, sex also prompts production of estrogen, which can reduce the pain of PMS.

Less-frequent colds and flu: Wilkes University in Pennsylvania says individuals who have sex once or twice a week show 30% higher levels of an antibody called immunoglobulin A, which is known to boost the immune system.

Better bladder control: Heard of Kegel exercises? You do them, whether you know it or not, every time you stem your flow of urine. The same set of muscles is worked during sex.

Better teeth: Seminal plasma contains zinc, calcium and other minerals shown to retard tooth decay. Since this is a family Web site, we will omit discussion of the mineral delivery system. Suffice it to say that it could be a far richer, more complex and more satisfying experience than squeezing a tube of Crest–even Tartar Control Crest. Researchers have noted, parenthetically, that sexual etiquette usually demands the brushing of one’s teeth before and/or after intimacy, which, by itself, would help promote better oral hygiene.

A happier prostate? Some urologists believe they see a relationship between infrequency of ejaculation and cancer of the prostate. The causal argument goes like this: To produce seminal fluid, the prostate and the seminal vesicles take such substances from the blood as zinc, citric acid and potassium, then concentrate them up to 600 times. Any carcinogens present in the blood likewise would be concentrated. Rather than have concentrated carcinogens hanging around causing trouble, it’s better to evict them. Regular old sex could do the job. But if the flushing of the prostate were your only objective, masturbation might be a better way to go, especially for the non-monogamous male. Having sex with multiple partners can, all by itself, raise a man’s risk of cancer by up to 40%. That’s because he runs an increased risk of contracting sexual infections. So, if you want the all the purported benefits of flushing with none of the attendant risk, go digital. A study recently published by the British Journal of Urology International asserts that men in their 20s can reduce by a third their chance of getting prostate cancer by ejaculating more than five times a week.

While possession of a robust appetite for sex–and the physical ability to gratify it–may not always be the cynosure of perfect health, a reluctance to engage can be a sign that something is seriously on the fritz, especially where the culprit is an infirm erection.

Dr. J. Francois Eid, a urologist with Weill Medical College of Cornell University and New York Presbyterian Hospital, observes that erectile dysfunction is extension of vascular system. A lethargic member may be telling you that you have diseased blood vessels elsewhere in your body. “It could be a first sign of hypertension or diabetes or increased cholesterol levels. It’s a red flag that you should see your doctor.” Treatment and exercise, says Dr. Eid, can have things looking up again: “Men who exercise and have a good heart and low heart rate, and who are cardio-fit, have firmer erections. There very definitely is a relationship.”

But is there such a thing as too much sex?

The answer, in purely physiological terms, is this: If you’re female, probably not. If you’re male? You betcha.

Dr. Claire Bailey of the University of Bristol says there is little or no risk of a woman’s overdosing on sex. In fact, she says, regular sessions can not only firm a woman’s tummy and buttocks but also improve her posture.

Dr. George Winch Jr., an obstetrician/gynecologist in Elko, Nev., concurs. If a woman is pre-menopausal and otherwise healthy, says Dr. Winch, her having an extraordinary amount of intercourse ought not to pose a problem. “I don’t think women can have too much intercourse,” he says, “so long as no sexually transmitted disease is introduced and there’s not an inadvertent pregnancy. Sometimes you can have a lubrication problem. If you have that, there can be vaginal excoriation–vaginal scrape.”

Women who abstain from sex run some risks. In postmenopausal women, these include vaginal atrophy. Dr. Winch has a middle-aged patient of whom he says: “She hasn’t had intercourse in three years. Just isn’t interested. The opening of her vagina is narrowing from disuse. It’s a condition that can lead to dysparenia, or pain associated with intercourse. I told her, ‘Look, you’d better buy a vibrator or you’re going to lose function there.’”

As for men, urologist Eid says it’s definitely possible to get too much of a good thing, now that drugs such as Viagra and Levitra have given men far more staying power than may actually be good for them.

The penis, says Eid, is wonderfully resilient. But everything has its limits. Penile tissues, if given too roistering or prolonged a pummeling, can sustain damage. In cases you’d just as soon not hear about, permanent damage.

“Yes,” says Dr. Eid, “It is possible for a young man who is very forceful and who likes rough sex, to damage his erectile tissue.” The drugs increase rigidity; moreover, they make it possible for a man to have second and third orgasms without having to wait out intermission.

“I see it in pro football players,” says Eid. “They use Viagra because they’re so sexually active. What they demand of their body is unreasonable. It’s part of playing football: you play through the pain.” This type of guy doesn’t listen to his body. He takes a shot of cortisone, and keeps on going. And they have sex in similar fashion.”

There’s a reason the penis, in its natural state, undergoes a period of flaccidity: That’s when it takes a breather. The blood within it is replenished with oxygen. “During an erection,” explains Eid, “very little blood flows to the penis. During thrusting, pressure can go as high as 200 mil of water. Zero blood flows into penis at that time.” To absorb oxygen, the tissue must become relaxed. “If you do not allow the penis to rest, then the muscle tissue does not get enough oxygen. The individual gets prolonged erections, gets decreased oxygen to tissue, and could potentially suffer priapism.” (We recommend you get a medical encyclopedia and look it up.) “The muscle becomes so engorged, it’s painful. Pressure inside starts to increase. Cells start dying. More pressure and less blood flow. Eventually the muscle dies. Then there’s scarring. That’s why it’s considered an emergency.”