On Sunday this week, Digital Journal reported on a small study
that seemed to show that eating kale in excess could result in mild thallium poisoning in people who consumed the vegetable in prodigious amounts.
Not surprisingly, on Monday, the "kale hit the fan," so to speak. Mother Jones
, and Craftsman Magazine
were taken to task by Vox Science and Health
, who called the stories nothing more than a "crackpot theory" reeking of "bad science."
The main problem with Ernie Hubbard, the alternative medicine practitioner whose study was cited, is that he never offered any good evidence that would link kale to various diseases, says Vox, claiming also, that the science behind Hubbard's assumptions is "awfully flimsy, and has all the hallmarks of a bogus health scare."
Vox claims the supposed "link" between kale and various diseases is incredibly flimsy
Zeroing in on Hubbard's claims of finding high thallium levels in some urine samples of the patients he was testing in a "de-toxification" study, and further researching the 2006 Czech study
, Vox says Hubbard erroneously concluded that kale could be a "hyper-accumulator" of thallium.
Hubbard concluded that low-level thallium poisoning could be causing an array of symptoms seen in some of the people in his study. Vox takes offense at Hubbard's conclusions, saying what should have been done, a real scientific study, wasn't done at all. And Vox is correct on this key bit of information. Instead of fixating on kale as being responsible for all the illnesses he had documented, Hubbard failed to conduct a scientific study to prove his hypothesis.
There is no published research linking kale to heavy metal poisoning in humans
Digital Journal looked for published studies on kale and thallium poisoning, and while several studies, including the 2006 Czech study, did investigate the rate of accumulation of heavy metals, including thallium, in kale and other members of the cruciferous family to which it belongs, there have been no scientific studies connecting the consumption of kale to thallium poisoning.
One study, the Characterization of kale (Brassica oberacea var acephala) under thallium stress by in situ attenuated total reflection FTIR]
showed that the carbon dioxide consumption speed of kale leafs under thallium stress was obviously larger than kale plants not stressed with thallium.
Another study investigated the sources of human and environmental exposure to thallium.
This study went along with what Todd Oppenheimer, a writer with Craftsman Magazine said.
Thallium is present in the Earth's crust in small amounts, occurring in sulfide ores. There are actually very few ares on the planet where thallium is found in high levels naturally. Losses to the environment mainly occur from mineral smelters, coal-burning power-generating plants, brickworks, and cement plants, all producing emissions into the atmosphere. Emissions of thallium from industrial processes vary widely according to the type of industry.
The study concludes that In contaminated areas, the majority of vegetables, fruits, and meats contain less than 1 mg thallium/kg fresh weight. Concentrations are higher in cabbages (Brassicaceae), with up to 45 mg/kg reported in green kale. Food of plant and animal origin usually contains < 1 mg/kg dry weight and the human average dietary intake of thallium appears to be less than 5 µg/day.
So was Hubbards claims about kale a matter of bad science?
Digital Journalist Tim Sandle is a microbiologist, specializing in healthcare and general science. In May this year, he tackled "bad science" in his article, Op-Ed: A bar of chocolate a day helps you lose weight. Really.?
Sandle zeroed in on a spoof scientific study
by John Bohannon that went viral on the Internet. It was all a fake, from start to finish, but was picked up by journalists as being the truth. The fake study said that eating a bar of chocolate a day was helpful in losing weight.
"The lessons here, for the public, is to be skeptical and to check where the results of a study came from. The message for journalists is to critically assess sources, and not to become swept away by the exponential momentum that 'viral news' sometimes generates. Meanwhile, Bohannon's detailed account of how he created his media spin is well-worth reading," concludes Sandle.
Comparing apples to oranges, Hubbard's small study, while maybe interesting, shows us that it lacked the scientific basis to make it conclusive. He didn't make his results up to fool the public, but he didn't test his theory either. It still goes without saying that moderation in anything we consume, be it alcohol, sweets or kale, is a sensible road to travel.