This week, Harper's Bazaar published an article saying that "people are getting seriously sick from eating kale" because of its thallium content, a heavy metal that naturally occurs in soil. So should we all stop eating this favorite veggie, darling of both the foodie and wellness worlds?
Here's the real story.
Where do heavy metals come from?
Metals are part of nature and are found in the earth’s crust. A heavy metal is defined as a chemical element with a specific gravity that is at leastfive times that of water. They are in the soil (for example, iron, copper, lead, thallium, cesium) and therefore end up in food grown in soil.
Heavy metals like mercury are also byproducts of industrial production — coal burning in the case of mercury — and end up polluting our oceans and bioaccumulating in the fatty tissue of larger fish, such as tuna, swordfish, and grouper.
Mercury is also present in a preservative called Thimerisol used in certain vaccines (like some varieties of the flu vaccine), as well as in the old style of metal cavity fillings in our teeth.
Arsenic, on the other hand, is commonly found, predominantly in its organic form, in rice and other grains and vegetables. It is also a famous poison in its inorganic form. Inorganic arsenic, like organic arsenic, is naturally occurring, but is more harmful to people than organic arsenic.
Arsenic levels in people are on the rise due to rice and fish consumption, but if the arsenic is predominantly organic, it must be at very high levels to cause physical problems. Most people will just pee out the organic form before it becomes a problem.
Still other metals are essential nutrients in our diet. Zinc, B12 (which contains cobalt), Iron, Manganese and Molybdenum are metals and are all essential for the function of human metabolism, energy production, and liver function. That said, all of them can be toxic to our bodies at very high levels.
Do metals make us sick?
When metals accumulate past certain levels, they can cause symptoms as varied as nerve damage and pain, nausea, vomiting, headaches, fatigue, thyroid dysfunction, and even kidney failure and cancer. Click here for a list of metals and their associated symptoms if they accumulate to toxic levels.
It is rare, however, for people to have enough exposure to metals to get such serious symptoms, unless they have contaminated water supplies (such as in Bangladesh, where water is contaminated with arsenic) or they have an occupational exposure, such as mercury fumes in industrial settings.
Luckily our bodies have great mechanisms for detoxifying us from heavy metals, and only in a small number of people do they accumulate to the point that they are harmful.
The real issue is that for more and more of us, our poor diets, bad digestion, and inflammatory, sedentary lifestyles are leading to the accumulation of low levels of metals causing early, low-grade biological stress and dysfunction, rather than actual toxicity.
The Bazaar article gives one example — literally one person — who was affected by thallium levels possibly because of, but not proven to be due to her cruciferous veggie heavy diet. In science, this is known as the "N of 1" fallacy. One person's one case is not an argument or even an explanation.
What it actually is, is an example that should lead us to ask deeper questions.
So what do you do about metals?
At practices like mine, Parsley Health, we test for heavy metal levels. If we find they are high, we help people detoxify from them, which means supporting their underperforming natural detoxification mechanisms with targeted nutrition, nutrients, and sweat.
It also often means healing leaky gut, reducing inflammation, and supporting a basic biochemical process called methylation, which many people do not do well genetically. We also test your genetics to see if you are a poor methylator.
What about IV heavy metal chelation?
Many people can successfully detoxify from low-grade mercury overload just with sauna treatments and digestive support alone, and while some people go so far as to get intravenous (IV) treatments for metal levels, for most people I have not seen IV treatments be necessary.
What I have seen be effective is the step-by-step process we offer at Parsley of healing the gut, lowering inflammation, supporting methylation, and optimizing diet, sweat, and stress.
If you are concerned about metals, get tested at a functional medicine practice, and once you know your levels, work with a doctor to decide if detoxification is right for you.
Also be aware that detoxifying metals can cause fatigue and can worsen other symptoms, and should never be done if you are pregnant. I also advise against doing any aggressive detoxification in older people, especially women, as pulling metals out of the body means pulling them out of bone where 95% of our body's lead is stored, potentially compromising bone strength and structure.
So what about kale?
Don't throw out your favorite leafy green just yet.
If you detoxify well, eat a high fiber (30-50 grams per day) diet, which is low in sugar and anti-inflammatory, if you have an intact intestinal lining and no "leaky gut," if you move and sweat regularly, and you routinely deal with stress in a healthful, nontoxic way (aka meditation, not doughnuts and wine), you should not be overly concerned about metal levels in kale or other cruciferous vegetables.
If you are concerned about your intake metals from these foods or another source, or have symptoms of fatigue, hormonal imbalance or immune dysfunction, it's worth getting your metals tested, and potentially working with a doctor to supervise a gentle detoxification program.
The first step in that program? Figuring out the source of your exposure and ending, or limiting it.