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Protein supplements and supplemented or fortified foods are often the subject of concern for heavy metals but contrary to popular belief low levels of various heavy metals are common in nature and in many of the natural foods we eat day-to-day. Protein powders are supplemented foods, when made from quality ingredients, with good provenance and manufacturing standards are generally consistent with these normal levels of heavy metals also found in food.

Previous analysis had suggested that some plant-based proteins had detectable levels of lead and other heavy metals, and there has been some discussion on social media channels about the levels of heavy metals in various proteins. Much of this recent discussion has centered on Proposition 65, a California State legislation which specifies maximum allowable amounts of various chemicals in food, that are known causes of cancer, birth defects or other reproductive harms.

Proposition 65 (officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986) came into force in California in 1986. The act intended to safeguard the safety of the State’s drinking water from contamination with chemicals known to cause cancer, birth defects or other reproductive harm and requires businesses to inform Californians about exposures in their products to these chemicals. Certain levels of listed chemicals trigger whether a warning (applied to a product) is justified according to Proposition 65. If a business, product, or service cause exposure to listed chemicals greater than this ‘safe harbour level’, a business must provide a Proposition 65 warning. If there are no ‘safe harbour levels’ listed, the business that exposes individuals to that chemical are also required to provide a Proposition 65 warning (unless the business can show that the anticipated exposure level will not pose a significant risk of cancer or reproductive harm). Businesses are also discouraged from providing a warning that is not necessary—for example, if there are trace, negligible amounts of a chemical in a product that is below the trigger level and not likely to expose someone to harm.

A bit of background on heavy metals

‘Heavy metals’ are technically metals with high densities, atomic weights, or atomic numbers, but what functionally considered heavy metals differs depending on various criteria and expert opinions. Essential nutrients like iron, cobalt, and zinc are heavy metals and yet are toxic in large doses. Typically, though, when people refer to heavy metals in the context of health, they are referring to metals such as lead, cadmium, arsenic, and mercury, which are toxic in even relatively small amounts. Interestingly though, while we do generally want to avoid exposure to these chemicals, they can be relatively ubiquitous in many foods, water, and in the environment in trace amounts. In extremely small amounts they might act as essential or conditionally essential nutrients too. However, modern processing of goods and environmental pollution can accumulate these toxins into dangerous amounts. So, in the case of heavy metals, the adage, the poison is in the dose, is very appropriate!

The common heavy metals


Elevated levels of this mineral are highly toxic and dangerous. However, arsenic is found in minute doses in many foods and drinking water and exposure to these normal amounts is not considered a risk to human health. Arsenic (As) is also likely to be recognized as an essential trace nutrient.1 Based on mammalian studies, a recommended dose of arsenic per day for health would be between 12.5 and 25 μg, and people take in around 12-50 μg per day through a normal diet.1, 2 The World Health Organization (WHO) has set a safe limit of <10 μg /L for drinking water.


Cadmium (Cd) is a heavy metal found commonly in the environment both from natural occurrence and contamination. Smokers have the highest exposure to cadmium, while standard foods are the highest source of cadmium for the non-smoking population. Foods contributing most to dietary cadmium are cereals and cereal products, vegetables, nuts and pulses, starchy roots or potatoes, and meat and meat products. Due to their high consumption of cereals, nuts, oilseeds and pulses, vegetarians can have a higher dietary exposure to this heavy metal.

Cadmium contamination is of concern because it can cause kidney failure, bone demineralization, and is a carcinogen. The average levels in food are approx. 200 μg/kg.3 Like arsenic, cadmium is fairly ubiquitous in the diet and is stored by some marine organisms and plants as an essential nutrient that functions in these organisms similarly to zinc,1 although cadmium isn’t likely to be an essential nutrient for humans. A tolerable amount of 7 μg/kg body weight, per week, has previously been set by the European Food Safety Authority, or around 76 μg per day.


Lead is a major contaminant of drinking water and food and is extremely toxic at even small doses. It has been shown to hinder neuronal development, particularly in infants. However, like arsenic, lead is proposed as an essential nutrient (in minuscule amounts) for a wide range of organisms.1


Mercury poses severe risks to the development of children in utero and early life. A tolerable amount has been set by the World Health Organization of 1.6 μg/kg body weight, per week,4 or around 17 μg per day for an average weight woman.

How Does Clean Lean Protein Compare?

Heavy metals, including lead, are found in many natural foods including fruits and vegetables, grains, and nuts and seeds. They are also found in lesser amounts in meat, seafood, and dairy products. Because heavy metals are naturally occurring in soil, inevitably small amounts will be absorbed into many foods that we eat every day and Clean Lean Protein contains equivalent or smaller amounts of lead than many common foods (based on testing of a sample of Just Natural Clean Lean Protein).

The pea protein isolates used to create Clean Lean Protein comes from sustainably cultivated European golden peas grown in Northern France. They are grown in soils that do not have high natural contents of heavy metals. Nor is the environment (air, water, soil) contaminated in any other way. The farmers are committed to sustainable production methods that minimize any use of pesticides or artificial fertilizers and from an environmental and water usage perspective, peas are among the most sustainable of crops.

Nuzest regularly tests products for safety including heavy metal levels, allergens and contaminants and the exposure to any heavy metals from Clean Lean Protein is below the thresholds advised by the World Health Organization.

heavy metals comparison table

*Based on Smooth Vanilla flavor, COA Dec. 2020

Clean Lean Protein also regularly tests at or below the stringent Prop. 65 levels. However, because it is sourced from peas which are grown in soil, each batch may contain varying levels of heavy metals. Just to be safe that a batch does not contain a higher level than what is allowed in the state of California (because it is made from a naturally grown pea that can have variations) Nuzest has chosen to put a Prop 65 label on its products, (despite tests that have come back at safe consumption levels).


The levels of exposure to various chemicals as defined by Proposition 65 are far more restrictive than those suggested by other health organizations, including those of the World Health Organization. Despite this, habitual, usual intakes (e.g. one serve per day, every day) of Clean Lean Protein would not exceed the ‘safe harbor’ level for these chemicals. Clean Lean Protein is, therefore, not only safe for consumption but offers a convenient, digestible, high-quality protein that is also free-from the major allergens and practically free from anti-nutrients. In fact, the levels of heavy metals in pea proteins like Clean Lean Protein are consistent with or less than those found in many common foods including fruits, vegetables, and tubers.


  1. Hunter P. A toxic brew we cannot live without. Micronutrients give insights into the interplay between geochemistry and evolutionary biology. EMBO Reports. 2008;9(1):15-8.
  2. Uthus EO. Evidence for arsenic essentiality. Environmental geochemistry and health. 1992;14(2):55-8.
  3. IARC. Cadmium and Cadmium Compounds. WHO International Program on Chemical Safety; 2012.
  4. Organisation WH. Exposure to mercury: A major health concern. Geneva, Switzerland: World Health Organisation; 2007.

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