 me, is a disease unique to humans. Why do humans get acne? Well, think about the distribution of those greasy sebaceous glands, face, chest, and back, exactly the same structures that pose the greatest obstruction during childbirth. So hey, maybe having a little extra lubrication at those sites would help make the baby more slippery for birth, conferring a selective advantage for successful delivery. OK, but what triggers them to become inflamed into zits later on? While in Westernized societies, acne is a nearly universal skin disease afflicting up to 95% of teens, and some populations eating more traditional diets, not even single cases could be found. This suggests that perhaps nutrition counseling should be a first-line therapy for individuals with mild to moderate acne. And it looks like it's the high-glycemic foods and dairy products. So we're talking sugar, soda, refined junky carbs, white flour, breakfast cereal, and dairy products like milk cheese, yogurt, whey, as well as saturated and trans fats concentrated in meat, dairy, junk, and fast food. So for example, acne patients should be encouraged to discontinue any whey protein supplements that might be taking the relationship between milk and acne severity, maybe explained by the presence in dairy of normal reproductive sex steroid hormones or the enhanced production of growth hormones, such as IGF-1. And if you're like, wait, I gave up dairy a month ago and still no change. It should be noted that changes in acne due to any dietary changes are likely to take at least 10 to 12 weeks, so you have to stick to it. Not surprisingly, acne patients are more than twice as likely to have a non-vegan diet compared to controls, but the difference did not reach statistical significance. So maybe the vegan's reading a lot of vegan junk? But what about this? Vitamin B12-induced acne. Our fellow great-ape herbivores like gorillas get all the B12 they need practicing the eating of feces, but my preference would be to take B12 supplements. And you don't have to worry about getting too much, because there are evidently no reports of adverse effects associated with excess B12 intake, but that's not true. First described back in the 1950s, about 1 in 10 people erupt in acne within days or even just within hours of getting an injection of vitamin B12, which then disappears rapidly when you stop injecting it. At the time, we had no idea what the mechanism might be. A problem still unsolved even up until just a few years ago, but then we finally figured it out. Vitamin B12 modulates the gene expression of the skin bacteria that cause acne. They swab the skin of 10 people before and after being injected with vitamin B12, turns out the level of B12 on your skin is proportional to the level in your blood. And so after injection, the bacteria on your skin have to make less of their own B12. And so the acne bacteria could concentrate instead on using its cellular machinery to churn out more compounds to attack your face. Without excess B12 on the skin, shown here in green, the bacteria has to make most on its own at the expense of porphyrins, which can trigger acne inflammation. When there's lots of B12 floating around the bacteria, they can not waste resources and focus instead on trying to pimple you up. OK, so wait, what do you do? Those on plant-based diets have to take supplemental B12, yes, but we don't have to get injections. Vitamin B12-related acne tends to occur only in dosages, in excess of 5,000 to 10,000 micrograms a week. Well, in excess of the 50 micrograms a day, I recommend or alternately my 2,000 single weekly dose. I mean, the only time you'd be taking between 5,000 to 10,000 a week is if you were treating B12 deficiency. If you remember from my previous video, B12 deficiency is treated with 1,000 micrograms a day for a month or more, and that could potentially trigger it, as noted in this vegan woman who wasn't taking B12. Developed B12 deficiency had to be treated with such high doses, her face erupted in acne. So all the more reason not to fall B12 deficient in the first place. But look, worse comes to worse, even if you do get B12 injections, the likelihood of it triggering acne may only be about 1 in 10.