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If recent headlines about heavy metals—like arsenic, lead, or cadmium—in your food have caught your attention, you may have a lot of questions. It seems shocking to hear that something so potentially dangerous could be in our food. While the facts are more nuanced than most news reports would lead you to believe, it’s true that we are all exposed to heavy metals on a regular basis. How concerned you should be about it requires a bit more knowledge. Read on to learn the basics of heavy metal exposure through food and what you can do about it.
Heavy metals are heavy elements. While some essential elements, such as zinc and iron, are technically heavy, the heavy metals that are of concern are elements that serve no biological function and pose a threat to health. Arsenic, cadmium, lead, and mercury are the heavy metals that pose the greatest threats to public health, and incidentally, are all on the World Health Organization’s (WHO) top 10 chemicals of public concern.1 Even though they are naturally occurring and found throughout the earth’s crust, human exposure to heavy metals that causes problems is mostly due to human activities like mining, smelting, industrial production, pesticides, etc.2
Yes. Heavy metals can produce health risks when we are acutely exposed to high levels, as in the workplace, which usually leads to severe and rapid onset of symptoms. Chronic low exposure over a long period of time can result in accumulation that poses a health risk too, but the symptoms may be more subtle. Each heavy metal comes with its own unique health risks, but they all have similar mechanisms of action for inducing toxicity, which involve the generation of free radicals and weakening of our own antioxidant defenses, leading to oxidative damage in a variety of tissues and organs.3 Heavy metal toxicity can cause digestive dysfunction, kidney dysfunction, nervous system disorders, skin lesions, vascular damage, immune system dysfunction, birth defects, and cancer.3
Heavy metals are in our air, water, and soil. They may also be found in the materials used to build our homes, the products we use, and sometimes our workplaces. They used to be found in common products such as paint and gasoline, which have left their mark on our environment today too. And because they are so ubiquitous in our environment, they are in our food. Foods can come in contact with heavy metals in a variety of ways. Heavy metals can fall onto food as it grows; they can be taken up by foods from the soil; they can contaminate the water used on crops; they may be in pesticides, fertilizers, or sewage sludge applied to non-organic food crops; and they may be present in some processing steps, packaging, or transport. In many foods, the concentration of heavy metals is very small, but in some foods it can be much higher.
Yes. The US Food and Drug Administration (FDA) does monitor the food supply and has set limits for heavy metals in many foods likely to be contaminated and/or consumed by high-risk groups (such as infants and children), although their guidance is limited beyond that. Similarly, the European Union and WHO have their own safety limits. California Proposition 65 has also established “safe harbor” levels for heavy metals and requires warning labels on any products that contain heavy metals (and other substances) at or above those levels. Although the warnings are legally required only for products sold in the state of California, many companies print one label for the entire United States, so consumers across the country may see these warnings. Proposition 65 limits are the strictest of the regulations.
For most people, mild exposure to toxic heavy metals is not a health risk, because our bodies are capable of clearing these toxins. However, heavy metals can be dangerous, especially when the load in our bodies exceeds our capacity to clear them and this can vary greatly from person to person. Children (including in utero and when nursing) are probably the most vulnerable population because children’s small bodies, slower metabolism, and rapid growth rates make them more susceptible to heavy metals’ effects. Exposure to heavy metals during active brain development is associated with learning and behavioral disabilities and lower IQ, in addition to other physiological effects.4 To know whether you should be concerned about heavy metal exposure, consider your general level of health, your age (older people tend to have accumulated higher levels than young people and may have reduced detoxification capabilities), and all the ways you might be exposed to heavy metals (including where you work, the air quality where you live, your water, your use of heavy metal-containing cosmetics or other chemicals, etc.).
Take sensational news reports with a grain of sea salt. The science around heavy metals can be confusing, and over the years, misleading reporting has introduced some significant flaws that have complicated the issue. For example, in a Consumer Report article from 2022, the reporting of lead and cadmium in chocolate was based on heavy metal limit numbers from California Prop 65 set in 1986, instead of the more recent and scientifically valid numbers established in 2018. The narrative (by relying on outdated standards) suggested that the naturally occurring trace amounts of lead and cadmium in certain chocolate bars and products exceeded the scientifically validated limits, which was not accurate. Most of the chocolate bars mentioned in that report actually fell comfortably within the established safety limits.
Another issue that is commonly confused in the public is differentiating between the different forms of these heavy metals. Heavy metals can occur in an organic or inorganic form (organic here refers to the chemical definition of containing carbon, not to organic growing methods) and for some heavy metals, such as mercury and arsenic, the form determines the toxicity. Inorganic arsenic is harmful to health and is a known carcinogen, while organic arsenic is much less harmful.5 In the case of mercury, organic mercury (most commonly found in food as methylmercury) is considered the most toxic form because it can reach the placenta and cross the blood brain barrier, while inorganic mercury cannot (although both can cause other harms).6 This is problematic when a report gives only “total” heavy metal levels without differentiating the amounts of organic and inorganic, because we don’t need to worry as much about some forms.
We can ensure that our bodies’ detoxification capabilities are supported every day by eating a nutrient dense diet built on vegetables, healthy fats, and proteins. Adequate sleep, plenty of clean water, and regular exercise also support detoxification. Beyond that, we can limit our exposure to heavy metals in meaningful ways by employing the following practices:
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