Kale is a superfood, a hipster’s delight, a juicer’s jam. But some of the biggest kale lovers out there may now be experiencing a kale fail.
The problem is not eating kale per se, but eating so much of it that you may be giving yourself low-level poisoning of the toxic heavy metal thallium. That can’t be good.
The issue is raised in an article in Craftsmanship magazine that was picked up by Mother Jones. The piece tells the story of a natural medicine researcher in the kale-loving San Francisco Bay Area whose patients complained of vague, similar problems like fatigue, foggy thinking, and digestive issues. The researcher, Ernie Hubbard, realized many of them had unusually high levels of thallium in their blood. Looking to find the cause, he turned up academic articles that showed how kale and its veggie relatives, such as cabbage and cauliflower, are particularly adept at taking up thallium from the soil. His patients were showing symptoms of “mild” thallium poisoning. When one patient stopped eating so much cabbage, her favorite food, she started to feel better as her thallium levels dropped.
This isn’t cause to toss away your kale chips, kale soda, and kale popsicles. There’s still work to do in showing what’s going on: Hubbard hasn’t actually established that excess greens consumption is actually causing his small group of patients to feel ill or how thallium is getting into the soil where kale grows. Also, as Mother Jones writer Tom Philpott points out, you’d have to be eating very high quantities for these kinds of health problems to become an issue.
Since that’s pretty much true of any food that has components that can be bad in large quantities (think: carrots, fish, and even water), this isn’t necessarily a huge worry. However, given how Jake Gyllenhaal fared on his all-kale diet, I wouldn’t recommend trying that soon.