Heavy metals are a broad term used to describe a group of naturally occurring metallic elements. At low concentrations, certain heavy metals, such as iron, zinc, copper, and manganese, are essential for human survival but can become toxic agents at higher concentrations. Other heavy metals, such as arsenic, cadmium, lead, thallium, and mercury, inevitably end up in our bodies due to their presence in the environment and can induce toxicity once certain concentrations are reached. However, studies suggest that humans might need between 12.5 μg and 25 μg of arsenic. So it is really about the amounts we're exposed to in our environment. It is now possible to find traces of toxic heavy metals in virtually all foods and beverages, lead and mercury being the most common.
The primary contaminant issue for dietary supplements is lead. This heavy metal is ubiquitous in the world environment, and its widespread presence is believed to be largely – but not entirely – due to the activity of man over the past millennia. Lead is naturally occurring in rocks that make up the Earth's crust, mostly in the form of minerals. These minerals can be spewed into the atmosphere by erupting volcanoes, eventually settling onto agricultural soils and reservoirs. Rain, which must filter down through topsoil and rock on its way to replenish aquifers that provide 99% of our groundwater for drinking, can also pick up traces of lead along the way. Lead is now found in all plants tested, whether plucked from the land or dredged from the sea. It is found in all animals and all humans. It is natural and unavoidable, yet our exposure to it has increased due to lead's use in man-made chemical compounds that have a number of industrial applications.
The human body can excrete lead almost as quickly as it comes in. This is an adaptation developed over millions of years of human evolution in response to the natural presence of lead in the environment. In 30 days, the blood level of lead is cut in half. While it's true that toxic exposures are unavoidable and can, at high amounts, overwhelm our natural detoxification systems, it's also true that there's a lot we can do to reduce our toxic exposures and support our detoxification system. It is important to purchase plant-based supplements that put raw materials through multiple layers of microbiological and heavy metal analyses, along with using good manufacturing practices (GMP) to ensure the lowest content of naturally occurring heavy metals.