Alexis on the Sexes: Up all night

ALEXIS MCKINNIS , | Updated 6/18/2014

Hey, you got caffeine in my semen!

Q: My girlfriend gave me a blow job last night at bedtime. Then she couldn’t sleep all night. We were wondering if caffeine is in semen? I’ve been drinking this new unsweetened sparkling water (one a day) with 160 milligrams of “organic caffeine,” plus ginseng. I have a pretty high caffeine tolerance, but she doesn’t.


A: The energy drink is almost certainly your culprit, especially if her tolerance for caffeine is so low. Caffeine is an interesting drug — one of few everyday substances that has the ability to break the blood-brain barrier and make its way into our central nervous system. There, it blocks a neurotransmitter called adeno­sine (which makes us feel sleepy) and we perk right up. Caffeine simultaneously boosts the transmission of dopamine (a feel-good neurotransmitter), so it also improves our mood. These effects are immediate; it takes only 15-45 minutes to reach peak levels in the bloodstream. Caffeine also passes through cell membranes easily and permeates our organs almost as quickly as alcohol does. Because it’s so readily absorbed, the concentration of caffeine is the same everywhere in the body. This means that — you guessed it — the amount of caffeine in your semen is going to be equivalent to the amount in your bloodstream.

A little more science for you: The half-life of caffeine is about five hours. This means that it takes five hours for the concentration of it in your system to be reduced by half. Say you drink your 160 milligrams around 3 p.m., when most experts agree is the best time for a caffeine boost (more on that later). By 8 p.m., there’s still 80 milligrams of caffeine floating around inside you, including in the seminal vesicles and prostate, which is where semen is produced. You didn’t mention exactly what time your girlfriend gave you the royal treatment, but I’m guessing it wasn’t too much later than that. Factor in her low tolerance for the drug, and she’s going to have a little trouble sleeping after swallowing.

Interestingly, caffeine has a shorter half-life in nicotine users: closer to 3 hours. The two drugs have a love/hate relationship and will diminish the effects of one another. It seems like every heavy smoker I know is also a coffee or Diet Coke addict.

Unfortunately, it seems research on ginseng concentration and semen has been limited to the herb’s positive effects on sperm motility. Worried that your little swimmers are lazy? Ginseng can help. Also, ginseng has been proven to increase testosterone levels, so ingesting the herb really does increase libido. As far as keeping your girlfriend awake after a blow job, well, I’ll let you know when the scientific community decides to look into that one.

Most living creatures on Earth operate on a circadian clock. It’s an internal cycle of exactly 24 hours that syncs us up with our daily surroundings, such as when the sun goes down. The whole process in humans is mind-blowingly complex and the timing can vary slightly from one individual to the next. (Are you a morning person or a night owl?) However, one constant in the circadian clock is the release of the hormone cortisol three times a day. Cortisol makes us feel energized and alert, so ingesting caffeine during those times isn’t the best idea because your body doesn’t need the extra boost, and can even be unaffected by it. Instead, it would make more sense to get your jolts after your body’s cortisol levels have dropped. This occurs between 9 a.m. and noon, and again between 1:30 and 5 p.m. (depending on your circadian rhythm). Hopefully, for your girlfriend’s sake, you’re not touching the energy drinks any later than that.

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