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A recent observational study on acne reported a “statistically significant relationship [between] acne severity and dietary factors such as chocolate [and] dairy products”—both of which I have videos about. But this surprised me: sunflower seed consumption.

When I think sunflower seeds, I just think good whole-food source of nutrition found to lower cholesterol levels as much as almonds, which is pretty good. There are, however, right and wrong ways to eat them. If you sit down and eat a pound of unshelled sunflower seeds, just eat them with the shell still on, you can end up corked, with “a fist-sized mass of shredded sunflower seed shells.” How could a doctor diagnose such a thing? By the “colonic crunch” sign, of course. Sounds like a breakfast cereal served in hell. But, rather, it’s when you palpate “a large crunchy rectal mass.” I’ve got a picture for you, of course.

Can end up “a sharp, thorny mass,” which is why the so-called “sunflower seed syndrome” has been described as “a prickly proctological problem,” lamenting that “[p]eople who consume health foods occasionally fall into the trap of believing ‘if some is good, more is better.'” It’s not the amount, though; it’s how they’re eating them: with the shells still on. That’s why “the syndrome is uncommon, unless the patients are children [who don’t know any better] or adults who are either impaired or have no experience with eating sunflower seeds.”

Most cases involve younger children, but here researchers describe a “psychologically sound” 13-year-old, stressing “the importance of the role of the parents [to guide] their children…about the potential problems associated with the ingestion of [too many] unshelled seeds.”

You can overdo even shelled seeds, though. Because of just the nature of sunflowers: they’re good at drawing the naturally-occurring heavy metal cadmium out of the ground. So, sunflowers end up with higher levels than most foods, even if grown in relatively uncontaminated soil. Though people who consume large amounts of sunflower seeds don’t seem to suffer any untoward effects, or even end up with detectably higher cadmium levels, here they defined large amounts as greater than an ounce a week, which is like a handful—about 150 seeds.

The World Health Organization recommends staying below about 490 micrograms of dietary cadmium a week. Even if you ate a handful a day, you’d be well below that, but you may get as much as 36 micrograms a day from the rest of our diet. So, I think one handful a day of sunflower seeds is a reasonably safe upper limit.

Yeah, but will it give us acne? You don’t know, until you put it to the test. Yeah, but who’s going to do a randomized, controlled trial of sunflower seeds and acne? Nobody…until, now.

After all, “consuming sunflower seeds is a very enjoyable way of participating in a clinical trial.” Fifty young adults were randomized to eat sunflower seeds—or not—for a week. In the control group, the acne severity index stayed about the same, but in the sunflower seed group, they got worse. This translates into about three extra pimples in the sunflower group versus about one extra in the control group. The researchers conclude that sunflower seed intake appears to aggravate acne; however, further evidence may be needed before “ban[ning] sunflower seed intake in patients with acne.”

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