The Vegetable Detective, Take Two
A California biologist found toxic levels of heavy metals in kale, got slammed for it on the internet, and then found evidence that at least one of the toxins could be even more troublesome than he had thought.
Written by TODD OPPENHEIMER
Photography by CLAIRE BLOOMBERG
Editor’s Note: By traditional standards, food and farming are odd topics for a magazine about craftsmanship. So before you read this update to “The Vegetable Detective,” a controversial story that appeared in our Summer 2015 issue, it might be worth explaining why we’re giving these subjects such attention.
If craftsmanship is about perfection—if it’s about careful thinking, making things that matter and are built to last—then few subjects deserve the rubric of craftsmanship more than our food production systems. As the great agrarian philosopher Wendell Berry once put it, “a good farmer is a craftsman of the highest order, a kind of artist.” In today’s world—where crops are beset by climate change on one front and assaults from chemicals and other industrial detritus on the other—a farmer’s efforts at craftsmanship are more challenging than ever. This is why we devoted our entire debut issue to a collection of pioneers in sustainable agriculture. And it’s why we stayed in touch with a scientist who found evidence that some of today’s most popular vegetables might, in certain circumstances, be toxic.
In the weeks since “The Vegetable Detective” was published (on July 8, 2015), it has provoked a variety of reactions—from numerous readers and, in particular, from the media. The article profiled a California biologist named Ernie Hubbard who had found indications that the cruciferous family of vegetables, possibly kale most of all, contained unusually high amounts of a toxic metal called thallium. And this metal might be causing a range of vague but increasingly common ailments—such as chronic fatigue, foggy thinking, heart arrhythmias, and, in extreme cases, hair loss and difficulty walking. Hubbard’s claims have now been reported—with either praise or condemnation—by at least two dozen media outlets, which range from new online sites to old, mainstream publications.
As is frequently the case, the media got hungry for a contrary storyline. The first to find one was Vox Media, which published an aggressive commentary on July 20, 2015 under the following title: “The viral idea that kale is bad for you is based on incredibly bad science.”
The first media response, from Mother Jones magazine, took Hubbard’s findings quite seriously. After doing his own literature review, Tom Philpott, the magazine’s food and agriculture correspondent, found enough evidence to warn readers against falling for the kale craze, especially in daily juices. This does not mean, Philpott added, that people should avoid kale and other crucifers altogether. “In all great things—wine, butter, ice cream, even kale—moderation makes sense,” Philpott concluded. And we would agree. Indeed, the people who came to Hubbard with problems all consumed crucifers in unusually large quantities, sometimes daily.
For a week or so, this assessment from Philpott, a respected food writer, spawned similar takes from publications as varied as Fast Company, Salon, Women’s Health, and Harper’s Bazaar. Then, as is frequently the case, the media got hungry for a contrary storyline. The first to find one was Vox Media, which published an aggressive commentary on July 20, 2015, under the following title: “The viral idea that kale is bad for you is based on incredibly bad science.” Vox argued that there was no peer-reviewed research backing the links Hubbard was making between kale and thallium toxicity; that Hubbard had “shopped around for lab results that would tell him what he wanted to hear,” eventually choosing a questionable laboratory that had been repeatedly challenged by lawsuits; and that “he is not a scientist.”
By this time, the internet was buzzing with fears that America’s latest health fad might be in trouble. And no one wanted that. Soon, a disparate collection of bloggers and websites attracted to food, health, truth, or controversy had picked up the Vox story, and were gleefully putting their own spin on the idea that all this talk about toxins in kale was based on crackpot science. Perhaps most curiously, before Vox and most others published their critiques of Hubbard’s work, none of them bothered to contact him to check the facts for themselves.
This fact inspired Hubbard to launch an attack of his own. He began by firing off a 13-page rebuttal to the Vox story, which, among other things, listed his 30-plus years of scientific credentials, and explained why he changed testing laboratories. (Apparently, judging from Hubbard’s laboratory reports, both of the labs he used reported the same measurements of thallium. So “shopping” for one over the other regarding thallium would have been meaningless. He chose the second laboratory, Doctor’s Data, because it could also test for other metals, and its services were less expensive.) While Hubbard did not discuss the controversy surrounding Doctor’s Data, it should be pointed out that the lawsuits and other complaints against this laboratory involve how its data sometimes has been presented, which we will discuss further in a moment. None of these complaints questioned the numerical accuracy of the laboratory’s tests. Those tests have been used by a number of highly regarded doctors and were the basis of our reporting.
When an issue provokes such extreme reactions from both sides, there is a good chance that all of the combatants have at least some truth on their side. That certainly seems to be the case when it comes to heavy metals in kale.
Hubbard concluded his rebuttal by asking Vox to retract or correct its story about him. After initially resisting Hubbard’s request, and then offering marginal changes, the editors eventually corrected their biggest factual errors. In the following weeks, Hubbard sent similar messages to a dozen other media outlets that were repeating Vox’s assertions. Each of them made corrections, and two of them pulled their stories entirely.
When an issue provokes such extreme reactions from both sides, there is a good chance that all of the combatants have at least some truth on their side. That certainly seems to be the case when it comes to heavy metals in kale, its cruciferous cousins, and perhaps many other vegetables as well. So let’s take a moment to summarize what we’ve been able to learn about the science on this debate since “The Vegetable Detective” was published.
The first question obviously involves the quality of Hubbard’s science. Perhaps the simplest answer to this question was delivered by Joshua Nachman, a nutritionist at Johns Hopkins University’s Integrative Medicine and Digestive Center. Nachman had occasion to quiz Hubbard about his work, in response to a query from The Huffington Post. After several exchanges, Nachman came to the following conclusion: “What he has found is good science,” Nachman told me. “It is preliminary, and not yet ready to be extrapolated to the population at large. But the chemistry is chemistry. It’s all factual.”
Now, exactly which facts are known at this point gets a little dicey. For starters, it should be remembered that ingesting small amounts of elements in the metals family does not always pose a problem. Some of these, such as iron, manganese, and zinc, are considered trace minerals, which are necessary nutrients. Any of these can be toxic if accumulated in excess, but most are easily excreted by the body’s natural detoxification systems (primarily the liver, kidneys and intestines, but also our skin, fingernails and hair). There is a third group of elements, however, such as lead and mercury, that is anatomically heavier than its cousins, which has earned it the title “heavy metals.” These are neither innocent nor easily eliminated. And there is evidence that thallium might be a particularly stealthy member of this family.
The reason, according to range of journal articles collected by Hubbard and his colleague, Dr. Michael Rosenbaum, has to do with thallium’s unusual chemical powers. (For a guide to this literature, please see our sidebar “Thallium, the cursed element.”)
In one of nature’s dark coincidences, the core of a thallium atom (specifically, its ionic radius) is exactly the same shape and size as a potassium atom. This enables thallium to essentially trick human cells into absorbing its atoms instead of potassium’s; once lodged inside our membranes, thallium binds with the sulfur in our cells, and hangs on for dear life. That’s when it starts to cause real trouble.
As our internal organs try to continue functioning as usual, the thallium interferes with several enzymes and vitamins crucial to energy production. (One is an enzyme called ATPase, which consumes up to 30 percent of the body’s energy.) In the meantime, while masquerading as potassium, thallium robs cells of their normal quotient of this nutrient, which is a key to energy levels. “I think I can conjecture that thallium has a strong impact on energy,” says Rosenbaum, whose specialty as a physician is biochemistry. “Mercury also binds to sulfur, but thallium is the only metal I know of that displaces potassium. It has a direct entry into cells. Other metals don’t. It disperses rapidly, and penetrates rapidly.”
With time, Rosenbaum says, our internal organs will gradually excrete thallium. Unfortunately, the process is quite slow because of a few other tricks that thallium has up its sleeve. On its way out of the body, a lot of it pauses and kind of reverses course, getting reabsorbed by the intestines through a process called enterohepatic recirculation. Thallium is such a stubborn guest that roughly half of what the kidneys filter out returns to the bloodstream.
All this chemical trickery has led Rosenbaum’s partner, Hubbard, to wax poetic about thallium—albeit from a rather diabolical perspective. “It plays bait-and-switch with our cells,” he says. “It’s like a sumo wrestler that looks like a leprechaun.”
All this chemical trickery his has led Rosenbaum’s partner, Hubbard, to wax poetic about thallium—albeit from a rather diabolical perspective. “It plays bait-and-switch with our cells,” he says. “It’s like a sumo wrestler that looks like a leprechaun.”
When it comes to getting this invisible wrestler out of your body, the science gets even more dicey. The human body may have difficulty naturally eliminating thallium, but there are some detoxification potions—called “chelating agents”—that can pull it out. As noted in our article, chelating agents have been extremely controversial, largely because the vast majority of them either don’t work or cause damage of their own. For this reason, the U.S. Food and Drug Administration recommends that only prescription chelating formulas be used, and only under the supervision of a knowledgeable doctor. And this is one of those cases where the extent, and leanings, of a doctor’s knowledge really matters.
Because of the bad reputation that some chelating agents have gotten, most doctors avoid them like the plague—ignoring the fact that there are some chelating agents on the market that are both safe and effective. At the same time, a good number of doctors inclined toward “alternative” medicine have recommended chelating agents too indiscriminately, and too liberally.
Some in this latter group have gone so far as to prescribe chelation, then test the patient’s urine, stool, or hair samples to evaluate toxicity. This ignores the fact that a chelating agent, if it’s potent, will push toxins into the body’s elimination pathways. Then, when a lab tests what’s coming through any of those pathways, urine in particular, the test results are likely to be exaggerated. (This seemed to be what happened with a patient of Hubbard’s featured in our original article; but in her case, her thallium counts were so high, the effects of chelation probably paled in comparison.) Nonetheless, these tests have been misused often enough over the years that a number of clinics and doctors have been fined or disciplined by their state medical boards.
Given all this confusion, one can’t help but wonder what guidance government agencies offer regarding how much thallium an average person can handle. Unfortunately, at this point there isn’t much.
Drinking water in the U.S. is regulated by both the U.S. Food and Drug Administration (for bottled water) and the Environmental Protection Agency (for tap water). And both agencies limit thallium to 2 parts per billion. This means that if farmers irrigate from municipal water sources, their crops will benefit from the same restrictions. However, a good many farmers irrigate straight out of the rivers, where all kinds of run-off accumulate—from roadways, wastewater discharges, and other farmers’ fertilizers, both organic and commercial. And no agency sets any numerical limits on the amount of heavy metals or other toxins that might show up in fresh vegetables.
When we wrote our original story, Hubbard suspected that fertilizers might well be the source of the thallium he was finding in kale, and that it was likely similar levels of this metal existed in kale’s cruciferous cousins. When we tried to follow this fertilizer trail to confirm Hubbard’s hunches, it led to a lot of black holes.
Federal regulations of organic fertilizers prohibit the presence of heavy metals, but they name only a few (thallium not being one of them) and don’t specify any thresholds. Fertilizer producers seeking organic labels must send their products to an organic certifier or, more commonly, to the Organic Materials Research Institute (OMRI), which handles product approvals for the U.S. Department of Agriculture. Unfortunately, OMRI does virtually no testing of its own, relying instead on outside laboratories. However, when those laboratories test products, they typically look for the nutrients that farmers want—such as nitrogen, potassium, manganese, and iron—not contaminants. “I think they [the fertilizer companies] do mix some stuff in there to make it fit within the parameters,” says Jonathan Lee, laboratory manager for Precision Enviro-Tech in Stockton, CA, one of the labs that does testing for OMRI. “I don’t think it’s one-hundred-percent organic.”
If there are any toxic metals in organic fertilizers, one would hope they wouldn’t travel all the way through the food system to land in our stomachs. An atom of thallium, for example, would have to start in some coal ash; land as fertilizer in a field of non-organic corn (which is allowed, and frequently done); get absorbed by the corn plant, and then pumped into its corn kernels; be harvested as feed corn and turned into chicken meal for Foster Farms or other poultry producers; get eaten and then pooped out by the chickens; be gathered as chicken manure to become an ingredient for organic fertilizer; then get spread on another set of fields to start the process all over again, this time for some leafy greens.
That trail covers a lot of opportunities for a metal like thallium to get diluted. The problem is that heavy metals don’t tend to dilute. “Metals will not decline,” Lee says. “They will travel along the path all the way.” This is what scientists mean when they talk about “bioaccumulation,” a problem that has brought us public health campaigns over the years on other heavy metals such as lead, mercury, and arsenic. Until there are some thorough studies of its path through our food supplies, one can’t help wondering whether thallium might also belong on that list.