Sometimes the things you’d never bring up in polite company are the most interesting. Case in point: semen. It’s one of those sex-related subjects that’s shrouded in so much mystery, it becomes even more intriguing. There are the obvious facts: it’s a major part of getting someone pregnant and has garnered a lot of laughs in movies. There’s Something About Mary, anyone? But beyond that, semen is actually one of those things that will probably make you marvel at how amazing the human body is. Read on for 12 semen facts you need to know.
1. Sperm and semen are two different things.
People often use the terms interchangeably, but they aren’t the same. “Semen is what’s produced by the penis during ejaculation,” F. Nicholas Shamma, M.D., a reproductive endocrinologist, infertility specialist, and founding member of IVF Michigan Fertility Center, tells Self.
Sperm, which are included in semen, are the microscopic tadpole-esque germ cells that are on a mission to fertilize an egg. They carry half the number of regular human chromosomes while eggs carry the other half so that a zygote will have a full set, says Shamma. If a sperm with an X chromosome fertilizes an egg, the zygote will be female, if the sperm carries a Y chromosome, it will be male.
2. Semen contains only around five to 10 calories per ejaculation.
That’s because it’s mostly water, Paul R. Shin, M.D., a urologist at Shady Grove Fertility in the Washington, D.C., area, tells Self. It’s also composed of sugars like fructose, prostate-produced proteins called prostaglandins, and enzymes, he explains. Overall, sperm makes up a very small portion of semen by volume (even though there are a ton of the tiny guys in there).
3. There’s a crazy amount of sperm in each ejaculation.
The average ejaculation clocks in at around 1.5 to 5 milliliters of semen, each one containing about 15 million sperm, says Shin. There’s such a boatload of sperm because even though it only takes one to fertilize an egg, there are plenty of booby traps along the way. “It’s a bit of an obstacle course to get to the egg,” says Shin.
First of all, a lot of the semen gets wasted—it doesn’t defy gravity and just stay in the vagina if the woman moves around. “The vagina itself is probably one of the most inhospitable of environments for sperm to live,” Mark Hong, M.D., a urologist in Phoenix, Ariz., tells Self. That’s because sperm’s pH is slightly basic while the vagina’s is slightly acidic. Without the addition of seminal fluid, which helps neutralize the vagina’s acidity, sperm would have a much tougher time making it through.
Then, whichever sperm survives that trek has to choose the correct fallopian tube to find the egg and actually be in good enough shape to fertilize it. That’s why it can take couples who are trying to conceive an average of five or six months, says Hong.
4. There isn’t usually sperm in pre-ejaculate.
In reality, that clear, sticky pre-ejaculatory fluid is made of prostatic secretions, aka fluid from the prostate, says Shin. With that in mind, it doesn’t mean you absolutely can’t get pregnant from pre-ejaculate—theoretically, sperm could be hanging out in a dude’s urethra from a prior ejaculation. Plus, the fact that pre-ejaculate doesn’t contain sperm doesn’t protect from sexually transmitted infections.
5. Sperm can survive for quite some time inside the female body.
They might be able to hang on for up to five days! “Sperm love to be in warm and wet environments,” says Hong. But outside the human body, they can only last for a manner of minutes, so don’t worry that they’re hanging out in hot tubs and toilet seats just waiting to get you pregnant.
6. Certain everyday things can damage men’s sperm.
Some of the top culprits: regular smoking, excessive heat (like working in front of a 400-degree oven all day or using hot tubs a few times a week), and being overweight. Also, even though it’s not scientifically proven, it might be smart for guys to keep laptops away from their actual laps. “It’s a bit controversial, but laptops generate a lot of heat,” says Hong.
7. Sperm goes from creation to ejaculation in about three months.
It’s the semen version of how when you’re looking at a star, you’re actually looking at light from years ago. First, it takes around 64 days for the male body to produce sperm, then around 24 to 28 more days for it to be transported and finally ejaculated, says Shamma.
8. There’s no scientifically sound way for men to change the taste or smell of their semen.
But if he’s healthy, it shouldn’t taste positively foul, either. Maybe not like doughnuts, but definitely not awful. “One consistent thing I understand will make it distasteful is smoking, probably in large part to different toxins,” says Shin. “But there has been no proof to say if you eat kiwi fruits, your semen tastes and smells lovely.” So really, it’s all anecdotal.
9. The consistency can change from day to day.
Hydration is one major factor in why a guy’s emissions can be a very slippery liquid one day and thick and gloopy the next—the more water he drinks, the thinner it will be. But this also comes down to a really cool physical mechanism. “Some of the semen is in a gelatinous phase until it meets up with prostate enzymes,” says Shin. When those combine, everything liquefies to a smoother consistency, but sometimes the process doesn’t finish before a man ejaculates. That’s why you may notice tapioca-like “pearls” or a gel-like consistency in semen, says Shin. If that semen were to hang out in the vagina, it would further liquefy to become more mobile.
10. You can’t freeze semen the way they do in movies and on TV.
That plot point of a single woman freezing someone’s semen in a thermos, then thawing it and whipping out the turkey baster? Not true to life. “We don’t recommend people [freeze semen] at home, because we freeze [sperm] in liquid nitrogen at something around -190 degrees Celsius,” says Shamma. If anyone DIYed it, the sperm would just die.
11. It’s extremely unlikely to be allergic to semen, but it’s possible.
If you were allergic to the stuff, you’d know it. “Some symptoms would be itching, swelling, and redness [in the areas the semen touches], much like with other contact allergies,” says Hong, who estimates that far less than one percent of women are affected by a semen allergy. People who have a semen allergy can be desensitized via exposure under the care of a medical professional.
12. Men produce a crazy amount of sperm in a lifetime.
The 95 percent of men who produce normal levels of sperm create around 2 trillion of the swimmers per lifetime, says Shamma. Yes, trillion with a “T.” “Out of those 2 trillion, they ejaculate something like 700 billion sperm,” he adds. That amounts to around 7.5 liters of sperm in a guy’s life, he says. Sperm production does decline as men get older, but that’s still a pretty impressive feat.
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