Kale
© Wikimedia CommonsCurly kale growing in the garden.
People who love kale, cabbage, broccoli and cauliflower often eat these vegetables on a regular basis. But over-indulgence may be dangerous. It may sound strange, but healthy-eating food addicts may be doing themselves harm.

A small study has found that if consumed in prodigious amounts, kale, and other members of the cruciferous family of vegetables to which it belongs, can be dangerous, and it doesn't matter if the kale is organic or not.

Biologist Ernie Hubbard is an alternative medicine researcher, living in Marin County, California. In 2010, he had the opportunity to conduct a study for a Cleveland-based company on a detoxification formula, called ZNatural. Hubbard is a molecular biologist with a background in biochemistry and genetics.

With his background, he was able to develop some tests not usually found in traditional laboratories, including "bio-impedence" analyzers that measure cellular energy and "chelating" formulas like ZNatural. While chelating formulas are controversial, ZNatural proved to be safe.

But it was during the testing phase of the product that Hubbard discovered something quite by accident, and that is the real story. Twenty volunteers were involved in the study conducted by Hubbard, and they happily peed into cups before, during and after the consumption of the ZNatural product.

Hubbard noticed an odd pattern in the testing of the urine samples. Several people had high levels of thallium and cesium in their urine, two heavy metals. "At first, I just thought 'Oh, another one of those.' By the third or fourth, I started scratching my head," Hubbard said.

The particular behavior of cruciferous vegetables

Smoothie
© Kale Smoothie Recipes/YouTubeA kale and banana smoothie.
The high levels of thallium stayed in Hubbard's mind. Further research by Hubbard uncovered a 2006 peer-reviewed study by researchers in the Czech Republic showing how the "cruciferous" family of vegetables behave as "hyperaccumulators" of thallium. The vegetables might include the more intense green vegetables such as kale, cabbage, broccoli, cauliflower, mustard, and collard greens.

These same vegetables are touted as a good addition to the diet because of their health benefits. These veggies are known to supply us with calcium, magnesium, potassium, Vitamin K, and various healthy phytochemicals and anti-oxidants. Kale consumption has literally exploded in health food circles. In all the studies Hubbard researched, cruciferous vegetables were found to have the ability to take up thallium and other heavy metals from the soil.

In 2007, only 954 farms across the country were harvesting kale, according to the USDA. By 2012, that figure had more than doubled, to 2,500 farms. Kale is now served in restaurants, with the number of establishments rising by 400 percent. Kale is juiced, used in salads and even made into chips. It was after learning all this that Hubbard had his "Eureka" moment, so to speak. "It suddenly hit me," Hubbard said, "I thought, 'Oh, my God!'"

Thallium has to get into the soil first before it's taken up by plants

Todd Oppenheimer, a writer with Craftsman Magazine says that while thallium is present in low levels in the Earth's crust, the primary way it gets into the soil in high levels is through "nearby cement plants, oil drilling, smelting, and, most of all, in the ash that results from coal burning."

Perhaps more importantly, is the question of quantity. One of Hubbard's test subjects had extremely high levels of thallium in her urine and mild symptoms of thallium poisoning. She called herself the "cabbage queen" because she ate it every day. She told Oppenheimer that when she cut "way back" on her consumption of her favorite vegetable, her thallium levels went down and her symptoms improved.

Symptoms of mild thallium poisoning include persistent but elusive problems, such as chronic fatigue, skin and hair issues, arrhythmias and other neurological disorders. But knowing the symptoms does not mean someone has the disease. Chemicals, industrial pollutants and agricultural pesticides are all around us.

Bernadette Burden, a press officer for the U.S. Centers for Disease Control and its investigative little sister, the Agency for Toxic Substances and Disease Registry, says, "A lot of these elements occur in nature. For example, we now know there is arsenic in apple juice. And in rice."

So where does all this information leave us? If would be safe to say that eating anything in prodigious amounts is unhealthy, from alcohol to food, in general. It might be better to remind ourselves that moderation in everything we do is safer, including eating kale.