A recent study highlighting the presence of heavy metals in many brands of protein in the US by the Clean Label Project (http://www.cleanlabelproject.org/ ) has drawn widespread attention.
TL:DR Don't freak out....the heavy metal levels in any of the proteins tested were low and similar to what you'd get from foods in your normal, daily diet.
What was tested?
134 of the top-selling brands of protein powder, compiled from Nielsen data and the Amazon.com best-seller lists, were tested for the presence of heavy metals; Arsenic, Cadmium, Mercury, and Lead.
What were the results?
Some of the key results included that over 70% of products had detectable levels of lead and cadmium and over ½ had detectable levels of BPA, with organic products showing higher levels of heavy metals. (Figure 1.)
But what does that mean…. really?
The study has highlighted the presence of various heavy metals in protein products available for consumption, BUT the presence of a heavy metal does not equate to toxicity in the body or harm resulting from it. Toxicity is defined by frequency, dose, and exposure to something. Even otherwise healthy nutrients are toxic in excessive amounts!
So, let’s drill down a little further into the data.
Heavy metals – the dose defines the poison! (and some are even essential!)
Arsenic sounds pretty scary and elevated levels of this mineral are highly toxic and very dangerous. But arsenic is found in minute doses in many foods and in drinking water. Arsenic is also close to being recognised as an essential trace nutrient. (1) Based on mammalian studies it is likely that 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)
In the study performed, even the highest recorded level of arsenic (59.2 ug/kg) which would equate to under 2 μg per serve of protein is only 8-12 % of the prospective recommended allowance for arsenic. The World Health Organisation (WHO) has set a safe limit of <10 μg /L for drinking water.
Cadmium (Cd) is a heavy metal found commonly in the environment from natural occurrence and contamination. Smokers have the highest exposure to cadmium with food being 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.
Cadmium contamination is of concern because it can cause kidney failure, bone demineralisation, and is a carcinogen.
The highest level observed in the study was 306.5 μg/kg, with most falling well below this, and comparing positively with the average levels that have been determined in food (approx. 200 μg/kg).(3) Like arsenic, cadmium is fairly ubiquitous in the diet and is actually stored by some marine organisms and plants as an essential nutrient that functions in these organisms similarly to zinc.(1)
A tolerable amount of 7 μg/kg bodyweight, per week, has previously been set by the European Food Safety Authority, or around or around 76 μg per day.
The highest cadmium containing product equates to around 9 μg per serve, or around 12% of the daily tolerable amount of cadmium.
Similarly, lead, a major contaminant of drinking water and food, and highly toxic at high doses; shown to hinder neuronal development, particularly in infants—might also be essential in trace amounts for a wide range of organisms.(1)
The highest amount of lead observed in any product in the study was 123.5 μg/kg, or around 4 μg per serve. The tolerable amount of lead per day is around 430 μg per day—or more than 10x the observed amount in a serve of the worst performing protein.
Mercury poses risks to the development children in utero and in early life. Mercury was not detected in the overwhelming majority of samples.
The highest observed reading was 26.6 μg/kg, or approx. 0.8 μg per serve. A tolerable amount has been set by the World Health Organisation of 1.6 μg/kg bodyweight, per week,(4) or around 17 μg per day for an average weight woman. The amount per serve in the highest detectable level of mercury is around 4% of this tolerable daily amount.
Overexposure to heavy metal contaminants is a major public health concern, particularly in the developing world. While we need to be vigilant to ensure that our food and the supplements we use are not exposing us to risk, this study and the way it has been interpreted and reported in the mainstream appears to be scare-mongering. None of the highest doses observed are amounts sufficient to cause harm and in all other cases the detected amounts were far lower. In fact, the observed amounts are, overall, consistent with what we might expect to see from normal, naturally occurring amounts of these minerals in food. Many of the detected levels were also below the Limit of Quantitation (LOQ) the minimum level at which results are determined to have a high chance of validity.
The study shows the presence of heavy metals in many protein supplements but the amounts, without exception, are too low to cause any risk. It is my opinion that this study and the reporting of it by the funders, is disingenuous at best.
Figure 1. Infographic from the Clean Label Project summary of study results.