Science

NSFW: The Truth About Semen

A gentleman’s relish is the true water of life. A nice shot of semen allows a man to pass on a genetic code through the ages, offering the closest thing to eternal life humans are ever likely to achieve. But such wonders aren’t straightforward. In fact, semen is a wonderfully complex secretion, rich in evolutionary history and packed full of healthy chemicals. And actually, there’s far more to it than sperm alone.

From Tiny Acorns

In the deep, dark past, physicians of the 18th century thought semen was concentrated from blood. In fact, one famed doctor, Samuel-Auguste Tissot, went as far as suggesting that “losing one ounce of sperm is more debilitating than losing 40 ounces of blood.” Yikes.

Fortunately, he was wrong. In fact, semen is a particularly complex excretion. It might shock you to find out that only one-to-five per cent of the average man’s ejaculate is actually sperm. The rest is rather delightfully referred to as “seminal plasma”, which is made up of over 50 different chemical compounds including, but not limited to, neurotransmitters, endorphins, hormones and immunosuppressants. Taken as a whole it is, without doubt, the seminal plasma which is both most interesting and most useful. In essence, the sperm is just a passenger.

But the jizz we all know and love isn’t held in the testicles. No, the delightful mixture is in fact concocted from a series of sources at the point of ejaculation, and not a moment earlier. First, the sperm — and just the sperm — passes from the testes, through a roller coaster of tubes: first the ejaculatory ducts, and on through the seminal vesicles. This is where the bulk of the seminal plasma joins the ride, shortly before the trusty prostate adds a few key enzymes, acids and lipids. Finally, the bulbourethral glands — what a mouthful — inject a little clear fluid into the urethra, which acts as a lubricant so the semen can spurt out with ease. Glorious, orgasmic ease.

The Big Wide World

Once released, of course, the semen is left to fend for itself — and the first thing it does is coagulate. In fact, studies have shown that the first fraction of the ejaculate doesn’t coagulate as efficiently as the rest of the semen — probably because it’s poorly mixed — but that the rest of it forms a thick, gloopy consistency as soon as it leaves the body. Given anywhere from five to 30 minutes, though, antigens present in the semen cause it liquify again.

The initial coagulation isn’t just for fun, of course — it’s tied up with the intended evolutionary purpose of the fluid. Most scientists agree that the reason it coagulates is so the semen can remain in place inside the vagina, enabling the sperm to have an easier trip to the cervix. Not just that, though: because it’s so thick, it also blocks the path for any previously deposited swimmers that happen to be lingering. In fact, the more often a man ejaculates, the stronger and longer the coagulation — an evolutionary trick which keeps the most prolific lovers on top of the pile. The subsequent liquefaction, in case you were wondering, then allows the sperm to swim more easily in their arduous race to the finish line.

That’s no easy journey, either. The female reproductive tract is a harsh environment, mainly because it’s rather acidic. Fortunately, semen itself is full of amines — alkali compounds — which prevent the sperm from dying in the vaginal acid bath. There’s also rather a lot of fructose within the seminal plasma, which helps give the little swimmers enough energy to reach their final destination.

Taste Test

But we’re not here to discuss the joys of conception — we’re here to get the lowdown on semen. And the female reproductive tract isn’t the only place it ends up. Let’s be brutally honest: Semen has made it into the mouths of many an individual, with mixed opinions over its taste and texture. Anecdotally, semen has been described as tasting “salty”, “bitter”, “sweet” or of “whatever the ejaculator ate twelve hours before.” But which one’s true? I mean, really, really true?

The wonderful scientific fact is: nearly all of them. All those chemical compounds that make it one of the body’s most complex excretions also serve to give it a unique flavour profile unlike anything else on Earth — and the exact taste is dictated by the subtlest differences, which vary man-to-man, day-to-day. Super-sweet? That’ll be the fructose. Salty? Excess sodium. Sharp-tasting? That’s the citric acid. Metallic? Ugh, zinc. Kinda detergenty? Blame the amines.

It is worth noting that the idea of eating particular foods to improve the taste of one’s semen, often peddled in glossy magazine, has no scientific backing whatsoever. Dr Debby Herbenick, sexual health educator at The Kinsey Institute and friend of Gizmodo, explains that she is “not aware of any scientific research that has been published in peer-reviewed journals that suggest… [ingestion of any food stuff makes] semen or vaginal fluids taste sweeter or generally more pleasant.”

Arguing For Ingestion

Taste alone is no reason to go near semen, then. But there is another reason why its ingestion might prove appealing. Amongst its 50 constituent chemicals are some that really can make you happy: cortisol (which increases affection), estrone (which elevates mood), oxytocin (ditto), and even serotonin (an antidepressant neurotransmitter). While that may sound good in theory, experiments also suggest that it has a real, measurable effect in practice.

A study published in the Archives of Sexual Behavior, for instance, showed that — even after adjusting for frequency and quanity of sex — women who have unprotected sex have fewer depressive symptoms than women that have protected sex, or no sex at all. Another, less rigorous, study hinted at similar effects in gay men who don’t use condoms.

Sadly, there’s been no scientific research conducted into whether oral ingestion of semen has an anti-depressive effect, though it seems likely that it may have at least some small positive effect. There is, however, genuine scientific evidence that suggests swallowing semen may make a woman’s pregnancy safer and more successful because she is absorbing her partner’s antigens. Good luck with that one.

A Note Of Caution

Before getting too excited about the possible health benefits of semen though, there is one problem that must be bought to your attention: HIV. You see, some of the protein factors within semen — principally prostatic acid phosphatase — make HIV far, far more potent than when the virus travels by any other means.

In fact, when HIV is carried in sperm it is a staggering 100,000-fold more potent than when it is not carried within seminal plasma. If that number scares you, it should: contact with semen is the single most effective way to transmit HIV. So while there seem to be some strong health benefits associated with direct contact with male ejaculate, caution is encouraged if get it from a stranger.

When you’re dealing with semen — a liquid so essential to human life and the endurance of the species — show some respect.

Image: Kamikaze Stoat under Creative Commons license