Sunning light on your butthole is a viral joke that has some science behind it

This week a viral tweet brought the internet’s attention to the practice of perineum sunning, also known as “butt-chugging sunlight.” The practice is quite simple: You moon the sun, exposing the anus to direct sunlight.

Practitioners claim it’s a way to get much needed Vitamin D. Metaphysical Megan, the Instagrammer whose image was attached to the viral tweet, captioned her own sunning with this endorsement:

30 seconds of sunlight on your butthole is the equivalent of a full day of sunlight with your clothes on!

Holistic coach Troy Casey also documented his butthole sunning on Instagram, and shares the claim that 30 seconds of sunlight beamed to the “mucous membranes of the anus” is the same as being in the sun all day.  

How sincere perenium sunners really are is debatable — after all, there are memes and Johnny Knoxville attached to the practice — and it’s likely a mix of devotees and people who just think it’s fun to expose their anus.

The real question is: Does butthole sunning actually do anything? 

Does the science check out?

Joshua Miller, professor and chair of nutritional sciences at Rutgers, tells Inverse that, essentially, it’s not so wacky to think you’d be better off with a bit of sun on your bum.

Miller says that the more skin area exposed to the sun, the more vitamin D will be synthesized per unit time. Presumably, Miller reasons, “exposing your backside to the sun will provide a relatively large amount of skin surface area, and thus lead to more vitamin D synthesis per minute than exposing, for example, just your hands and face.”

However, he notes, there is seemingly no evidence that different locations on the body have skin with different capacities to synthesize vitamin D per unit area.

It’s difficult to offer general advice when it comes to sun exposure and vitamin D synthesis because that interaction is dependent on variables like where you live, the time of day, your age, skin color, and the season.

That said, recommendations for sun exposure are typically in the range of five to 30 minutes of sun exposure a week — a recommendation balanced against the risk of skin cancer. It’s also possible that you’re not actually vitamin D deficient, even if you’re nervous you are.

Meet a Sun practitioner who “charges up”

Ryan Baesemann, a sometimes-practitioner, of what he calls “charging up” or “tanning your butthole,” was first exposed to the practice around 2012 while living in a communal space in Santa Cruz. He went out for his morning coffee, looked up, and saw his housemate’s “scrotums dangling.”

They called it “charging up” — something you can do in the wintertime to get more vitamin D because “it’s actually quite efficient to expose the part of your body that receives the least amount of time in the sun.”

Baesemann offers a tempered look at the butthole sunning, commenting that he thinks it’s funny and fun to do, and doesn’t do it seriously for health. But he does find if he finds his energy levels dwindling, and he’s awake in the morning with the sun shining, he’ll “charge up as a way to feel like I’m getting some warmth in my bones.”

Maybe, Baesemann says, it’s a placebo — but it also feels nice and is a body-positive way to “reclaim the butthole.”

Plus “it’s a fun thing to do with friends.” It won’t supersize your Vitamin D intake, and one should be careful not to get a sunburn, but there’s nothing so wrong with a small sunshine suppository.