It is not often you discover something you enjoy is also really good for your health, but researchers came up with startling results when looking at whether sex was good for your health, Forbes magazine has reported.

One of the most credible studies correlating overall health with sexual frequency, Queens University in Belfast tracked the mortality of 1,000 middle-aged men over the course of a decade.

The study was designed to compare persons of comparable circumstances, age and health. It's 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.

Others studies show that having sex even a few times a week may help 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, it's smell center.

- Reduced risk of heart attack. In a 2001 follow-on to the Queens University study mentioned above, researchers focused on cardiovascular health. Their findings? That by having sex three or more times a week, men reduced their risk of heart attack or stroke by half.

-Weight loss, overall fitness. 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 works the pelvis, thighs, buttocks, arms, neck and thorax. Sex also boosts production of testosterone which leads to stronger bones and muscles.

-Reduced depression. A 2002 study of 293 women reported by American psychologist Gordon Galllup showed that sexually active participants whose male partners did not use condoms were less subject to depression than those that did. One theory of causality: Prostoglandin, a hormone found 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 from 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. You've heard of Kegel exercises? You do them whether you know it or not, every time you stem your flow of urine. This same set of muscles is worked during sex.

-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, and concentrate them 600 times. Any carcinogens present in the blood likewise would be concentrated. Rather than having carcinogens hanging around causing trouble, it's better to evict them. A recent study published by the British Journal of Urology International asserts that men in their 20's can reduce by a third their chance of getting prostate cancer by ejaculating more than five times a week.