Avoiding kale, if not exactly a priority, has certainly been a factor on my task list, on the sensible basis that “flavorful,” that popular foodie term, does not, I believe, necessarily imply that the flavor in question is at all desirable.
But some foodies may soon be turning their backs on the stuff, not for flavor considerations, but for something a bit more intensive:
[A]lt-medicine researcher and molecular biologist Ernie Hubbard … began to notice an odd trend among some of his clinic’s clients in California’s Marin County, a place known for its organic farms, health-food stores, and yoga studios. Extremely health-conscious people were coming into to complain of “persistent but elusive problems”: “Chronic fatigue. Skin and hair issues. Arrhythmias and other neurological disorders. Foggy thinking. Gluten sensitivity and other digestive troubles. Sometimes even the possibility of Lyme Disease.”
Hubbard began to find detectable levels of a toxic heavy metal called thallium in patients’ blood samples at higher-than-normal levels as well as in kale leaves from the region. Meanwhile, “over and over,” he found that patients complaining of symptoms associated with low-level thallium poisoning fatigue, brain fog, etc. would also be heavy eaters of kale and related vegetables, like cabbage.
And he found, in the form of this 2006 peer-reviewed paper by Czech researchers, evidence that kale is really good at taking up thallium from soil. The paper concluded that kale’s ability to accumulate soil-borne thallium is “very high and can be a serious danger for food chains.” And here’s a peer-reviewed 2013 paper from Chinese researchers finding similar results with green cabbage; a 2015 Chinese study finding green cabbage is so good at extracting thallium from soil that it can be used for “phytoremediation” i.e., purifying soil of a toxin and a 2001 one from a New Zealand team finding formidable thallium-scrounging powers in three other members of the brassica family: watercress, radishes, and turnips.
Excuse me while I smile at “thallium-scrounging powers.”
Up until about the early 1970s, you could buy thallium sulfate at your local hardware store: it made a good rat poison. Turns out, of course, that it can poison lots of critters besides rats. Still, it’s not like the whole earth is just saturated with the stuff; while thallium is not exactly rare as elements go, the most common sources are industrial. One of those industries, however, is big in these parts: oil drilling.