One reason I love this topic is that I have centered my academic career around the thesis that aging is a socially-evolved phenomenon. Another is that it’s even more fun than intermittent fasting.
There has been a great deal of prejudice against this topic since the most popular evolutionary theory of aging  hypothesized (with scant evidence) a tradeoff between reproduction and longevity. Religious taboos probably have played a role as well. In insects, there is some evidence that sexual activity is associated with shorter lifespan. But we’re not insects, and the data for humans and other mammals supports a robust role for sexual activity as a promoter of longevity. (I last wrote about this topic in 2018.)
This is the classic longitudinal study by Davey Smith  which, to my knowledge, has not been replicated since. In males age 45 to 70+,“mortality risk was 50% lower in the group with high orgasmic frequency than in the group with low orgasmic frequency,” Twenty-five years on, there is no excuse for a corresponding study not having been performed for women, but there is indirect evidence that women, too, live longer if they have more intimacy and sex in their lives.
Enjoyment of intercourse was in the three top predictors of longevity in women . Women have been found to be more sensitive to the quality of loving attention and the depth of their connections in love, while men tend to respond to the cruder quantitative variable of sexual activity [ref]. Women (>57yo) who reported sexual relations that were highly satisfying had higher risk of cardiovascular disease, but women who reported most intense pleasure from sex had lower risk. “These findings challenge the assumption that sex brings uniform health benefits to everyone.”
I’ve been an advocate of the theory that aging is programmed by signal molecules in the blood. Only a few of these have been positively identified, and among these, the hormone oxytocin is probably best established as a longevity factor [thanks to the Conboy lab]. Oxytocin is expressed in experiences of intimacy, and also in childbirth. It’s not much of a stretch to guess that oxytocin is responsible for some of the health benefits of sex and intimacy.
It’s no surprise that competent erectile function is associated with less depression and higher quality of life in elderly men, but someone had to do the study. As you can imagine, it is difficult to establish a direction of causality. “For the time being, it cannot yet be proved that “good sex promotes good health” since good health also favors good sex.” [Gianotten 2021]
Long before modern methods and modern taboos
…there was an ancient literature associating sex with longevity.
In 1973, a Chinese tomb was excavated that had not been opened since 168 BC. Among other gems there in was the MaWangDui scroll. Harper translated and wrote about this scroll a few years later.
“The Mawangdui medical manuscripts bear the distinctive tendency of combining Daoist beliefs with medical knowledge. Some texts stress sexual intercourse as resembling the union of yin and yang. Others discuss sex’s benefits for physical well-being.” Although this, like all scholarly works of the era, was written from a male perspective, “the manuscripts emphasize the importance of women’s pleasure”. [ref]
The ms includes a poem which has been interpreted as a coded instruction manual for mystical sexual union.
There is a long Daoist tradition of sex ritual practiced to enhance health and longevity. There is also a prudish Confucian tradition which is scandalized, and seeks to suppress Daoist sexual practices. Consider this passage, already a thousand years into Daoism:
A man must not engage in sexual intercourse merely to satisfy his lust. He must strive to control his sexual desire so as to be able to nurture his vital essence. He must not force his body to sexual extravagance in order to enjoy carnal pleasure, giving free rein to his passion. On the contrary, a man must think of how the act will benefit his health and thus keep himself free from disease. This is a subtle secret of the art of the bed-chamber.
— Sun Si-miao, 7th Century Chinese scholar and medical researcher
Is it a pure rendering of the Daoist tradition, or is it tainted by defensiveness in the face of withering Confucian pressure?
“In the I Ching, the hexagram that symbolizes sexual union is the 63rd, called ‘Completion.’ It consists of the trigram for ‘water/woman/clouds’ placed over the trigram for ‘fire/man/light.’ This not only places Yin above Yang, it also suggests the image of water slowly coming to a boil over a fire. This is the quintessential Daoist image for human sexual intercourse, concisely symbolizing the essential differences between man and women in the sexual act. In order to last long enough to bring that cauldron of water to a rolling boil, the man must ration his fuel and carefully control his fire. If he burns his fuel too fast, his fire expires prematurely, leaving the water only lukewarm. But if he conserves his fire long enough to bring the water to a boil, then even the smallest flame suffices to keep it hot for a long time. — Daniel Reid
The yarrow tells of great good fortune now
(If not apparent yet, then very soon).
You’ve brashly prayed to God for Sun and Moon;
They’re granted! for your wish conforms with Dao.
You did not take the blame when things went wrong;
You must not gloat now that your luck has turned
No matter what you do, you won’t be burned,
But gains will be much greater if you’re “strong”—
Which just means “humble”—both connote the same.
To recognize that all depends on you,
Yet curb your will, avoid the urge to do,
Dissolve the Self, let intuition through,
Release control and laugh, forget your name—
No pride, no virtue, no judgment, no shame.
— poem by JJM, from the I Ching Sonnet Project
Denis Noble, a medical professor at Oxford University, has a recent article describing an ancient Oriental literature of sex and health, and placing them in a modern, scientific context. (Noble has been an articulate advocate for expanding the Darwinian tradition beyond the Selfish Gene.) He cites studies of telomerase activity related to physical intimacy and touts the powerful rejuvenation effects of spermidine on mitochondria, autophagy, and other aspects of aging.
Leslie Kenny is an Oxford medical researcher who is familiar with the ancient Daois traditions around sex and longevity. She
“wondered aloud whether the reason for arousal but non-ejaculation was so that the man would resorb his own spermidine and thereby benefit from a boost in cellular autophagy and the resulting beneficial biological effects. I too had wondered about the possible benefits of resorbing sperm to male health.”
Noble speculates about the traditional exchange of saliva in some of these ancient Chinese texts. Saliva contains exosomes, virus-like packets of DNA and proteins that transmit information both within the body and between individuals. The Chinese scrolls emphasize
slow and gentle movements, beginning with caressing of what seem to be the mysterious energy meridians within the body…Breath, gaze and heartrate between lovers become synchronised during foreplay until actual coitus occurs, but it would be harmful for the man to consummate the love act at this point. The text of Su Nu suggests that consummation should occur only 3 times out of 10, and only with a woman when wishing to conceive a child. All other uses of a man’s precious bodily fluids – in this case, semen – would be viewed as exhausting the man’s body, ageing it prematurely. Whereas a woman and her yin energy were greatly strengthened by reaching climax, this was to be avoided at all costs by the man, whose yang energy would be robbed.
“As the 20th-century French sinologist Marcel Granet put it, sex for the ancient Chinese was ‘far more sacred than for us’. It can be so once again for us too.”