Boxers or Briefs?

Boxers or Briefs?Believe it or not, it’s a question I get fairly often: “Grok didn’t wear tighty-whities. Should I?”

From time to time, I like to have some fun and expand the scope of this blog beyond the regular topics. Health and wellness, after all, come down to far more than just diet and exercise (and sleep and sun and stress, for that matter). So I’ve written about everything from the benefits of squat toiletsgoing poo-less, and stand-up workstations to the dangers of excessive sitting, nighttime light exposure, and passive living. Today, I’m going to branch out again. Today, I’ll attempt to answer what sages, wise men, gurus, and guys sitting around in gym locker rooms could not: boxers or briefs (or nothing at all)? So fill your cup and let’s dig in.

This topic was prompted by a reader’s email:

I thought this could be an entertaining topic.

We’ve all seen the Seinfeld episode where Kramer starts wearing boxers when Elaine tells him boxers are better for his sperm count.

Is there any hormonal drawbacks associated with briefs that could be caused by the low sperm count or vice versa?

Our ancestors were certainly “out there, and loving every minute of it.”


Here’s the Seinfeld clip in question:

Having watched that, I’m not even sure a post is necessary. Kramer pretty much covers it. Still, not everyone has access to YouTube at work, so I’ll continue.

I’m not going to discuss the subjective effects of wearing boxers, briefs, or nothing at all. People have their preferences. Some people like providing a safe, secure, snug house for their boys, while others take a more free-range approach. No value judgements cast here.

But what’s our natural state?

While it could be argued that going commando is “most natural,” seeing as how we’re all born in the Hanes-less state, I’d say that loose-fitting boxers are pretty close to natural, too. Loincloths were the earliest undergarments, and those were essentially just a piece of fabric loosely looped between the legs. Plenty of air flow and very little confinement. Grok’s private bits definitely breathed, whether he wore a loincloth or nothing. Okay, so one is more natural than the other(s), but does that make a difference for our health? Natural doesn’t always mean better, you know.

“Everyone knows” that wearing tight briefs reduces sperm count, and I briefly discussed this in a Dear Mark that asked about laptops and infertility. It’s true that scrotal heat stress does have the potential to affect sperm quality, count, and motility, as in men with varioceles – enlarged testicular veins that lead to excessive blood flow, elevated scrotal temperatures, and sometimes infertility – but it’s unclear whether choice of underwear represents a significant-enough thermal stress to the scrotum to induce negative changes. The questions we must ask are: does the choice of underwear truly affect scrotal temperatures? And if it does, is it sufficient to negatively affect male fertility? Let’s look at the evidence:

In one study, healthy young men wearing tight-fitting polyester-lined athletic support garments consistently displayed elevated scrotal temperatures between 0.8 and 1 degree C. This increase, however, did not affect any fertility parameters, including sperm concentration, sperm motility, sperm morphology, sperm viability, sperm hyperactivation, and the ability of sperm to penetrate hamster oocytes (sadly, no hamster-human hybrids were created throughout the course of this study).

Another study found no difference in scrotal temperatures between wearers of boxers and wears of briefs. In fact, the average temperature was actually a hair lower in the brief group, though it wasn’t significant. Fertility parameters all checked out, as well.

In another study, the author measured how various garments and positions affected his own scrotal temperature. Boxers were 0.5 degrees C cooler than briefs. Scrotal slit underpants were 1.2 degrees cooler than boxers. Sitting with thighs apart was 1.6 degrees cooler than sitting with thighs together. He didn’t measure his fertility parameters, however, so we don’t know whether or not those were affected.

And finally, a team of researchers studied the effects of boxers, briefs, and going commando on the scrotal temperatures of 50 healthy men without a history of infertility. They found conclusive evidence that wearing tight-fitting underwear such as briefs resulted in elevated scrotal temperatures, though it “remains to be elucidated whether these differences are linked to semen quality and consequently male fertility.”

Choice of fabric might make a difference, too. In an Egyptian study, one researcher used polyester slings (that allowed penis exposure but kept the scrotum confined) to induce azoospermia – the state of having no measurable sperm in semen – in previously fertile men. These were like briefs on steroids, fully preventing the tendency of the scrotum to “hang low” (which it does for thermoregulatory purposes). They caused the testicular temperatures to approach the rectal temperatures, which is way hotter than testicles are built to withstand and which apparently contributed to the infertility. But the author also thought that scrotal-polyester friction-induced electrostatic charges might have played a role as well. To figure out which was responsible, that same researcher did a followup study, this time using dogs in specially-fitted underwear. To eliminate the confounder of scrotal temperature, he made the underwear loose fitting. And sure enough, testicular temperature didn’t change much. Not even in the polyester group. The dogs wore the underwear for 12 months straight. Once again, the polyester underpants killed fertility (without affecting temperature), while cotton underwear dogs and control dogs (commando) experienced no change. I was alive during the seventies, and I can certainly vouch for the friction that occurs between bare skin and polyester.

As for the hormonal stuff? While scrotal temperature changes do affect follicle stimulating hormone, which controls sperm quality and count, they do not seem to affect testosterone levels. Fertility can be affected, but not via testosterone.

I wish I could give you an absolute proclamation, here, but I can’t. How about some general guidance?

  • If you’re having trouble conceiving, or your sperm count comes back low, and you wear briefs or some other tight-fitting underwear, switching to boxers, or cotton, or nothing at all might help. Either way, it’s not going to hurt.
  • Normal scrotal temperature – the kind that promotes fertility – is one or two degrees C below body temperature. As seen in the Egyptian study, once the scrotal temperature approached the rectal (body) temperature, fertility was impaired. The best way to measure your scrotal temperature is with an infrared thermometer, which can be a bit pricey.
  • Don’t wear tight fitting underwear – polyester or not – for 12 months straight. Give your boys some time off, whether that comes through targeted ice baths, walking around (walking and standing and even running lead to cooler scrotums than sitting) more, or switching to more forgiving undergarments.
  • Switch to a natural fabric, whether it’s cotton, animal skin, or nothing.
  • Don’t be in such a rush to always replace your underwear with a gaping hole in the crotch. It might actually be helping, especially if it facilitates scrotal drooping.

Thus, as is usually the case, there’s no right or wrong answer here. While wearing tight-fitting briefs can increase scrotal temperature, which can affect fertility, it’s not a sure thing. The research is unclear, and the ultimate choice rests in your hands. Go ahead and mess around with infrared thermometers if you’re really concerned, and get your sperm count tested, but you probably don’t have much to worry about as long as you’re adhering to the general guidelines listed above.

So, dear readers, what say you – boxers or briefs?

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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