 Sex is important to health, according to the Harvard Health Letter. Frequent sexual intercourse is evidently associated with reduced heart attack risk. But this seems to me the perfect case for reverse causation. They're implying that more sex leads to healthier arteries, but isn't the opposite more likely that healthier arteries lead to more sex? Blood flow in the penis is so reflective of blood flow elsewhere that penile Doppler ultrasound can predict cardiovascular disease. But low frequency of sexual activity may predict cardiovascular disease in men independently of a rectile dysfunction, suggesting that sex may be more than just fun, but therapeutic, or at least, so says an editor of the Journal of Sexual Medicine in discussing whether or not frequent sexual activity should be prescribed to improve general health. In men, they suggest, it's because more sex means more testosterone. When men make love, they get a big spike in testosterone levels in their blood, but interestingly, in contrast, they get no testosterone boost when they masturbate. This may be because testosterone increases with competitive success, like if you win at a game of sports. While sex is not usually regarded as a competitive event, one's mental state afterwards could nevertheless be something like that of a winner, as opposed to the mental state after masturbation. The spike in sex hormones in the blood is so great that men's beards actually grow faster on days they have sex. And since low testosterone levels are associated with increased risk of mortality, that could help explain the health benefits. So do men who have more sex actually live longer? I did a PubMed search for sexual activity and longevity, and came up with sexual activity and longevity of the southern green stink bug. Our taxpayer dollar is hard at work. But I was less interested in whether or not screw worms live up to their namesake and more interested in this, sex and death. A study whose objective was to examine the relation between frequency of orgasm and mortality defend that men with high orgasmic frequency appeared to cut their risk of premature death in half. And apparently the more, the better. 36% drop in mortality odds for every additional 100 orgasms a year. Conclusion? Sexual activity seems to have a protective effect on men's health. But not, it appears, if you cheat. Unfaithfulness in men seems to be associated with a higher risk of major cardiovascular events like heart attacks and strokes. Extramarital sex may be hazardous and stressful, because the lover may be younger and more exuberant, and secret sexual encounters may be more stressful. In a large autopsy series, the majority of cases of sudden death during sex occurred in men having extramarital intercourse. The absolute risk is low, only one out of 580 men might be expected to suffer such a death. But for those at high risk, sex in familiar surroundings at a comfortable room temperature and with one's usual partner may be safer. And speaking of safe sex, you thought drinking and driving was bad? Well, it's generally assumed that sexual behavior happens in parked cars. There's little discussion in the research literature of sexual activity in moving vehicles. About one in five college students report engaging in sex while driving, nearly half while going more than 60 miles an hour, including feats likely involving distraction. Researchers suggest maybe this is something that should be warned about in health class. When done right, though, love may protect your lover's life. Given the benefits of sexual activity, intervention programs could be considered perhaps based on the at least 5 a day campaign aimed at increasing fruit and vegetable consumption, although the numerical imperative may have to be adjusted.