Protein Powders and Heavy Metals: What the Latest Testing Shows (2024–25)

For the longest time, all regular consumers of nutritional supplements were able to live under the illusion that everything contained within their products of choice was accounted for on the label of the package. 

While several studies conducted over the years exposed the falsehood of this belief — at least with respect to unlisted performance enhancers, the fantasy was obliterated forever by the report of the 2024-2025 Clean Label Project, which made it plainly evident that there were harmful ingredients circulating through many of the most popular protein supplements on the market.

In particular, heavy metals like lead, cadmium, and arsenic, along with an array of toxic chemicals, were detected at intolerable levels in a shocking number of protein powders. This finding led many people searching for definitions as to the level of lead that is tolerable for human consumption, and it caused others to forgo the use of protein powders altogether out of the fear that they were progressively poisoning themselves with each rounded scoop.

With rumors and myths spreading through groups of fitness enthusiasts, the parents of young athletes, and communities on Reddit, it can be easy to misconstrue the results of the Clean Label Project report, and draw the wrong conclusions. That’s why it’s important to address the CLP’s data from the proper perspective, and produce a plan to capitalize on the information it provided.

Heavy Metals in Protein Powders: What the Data Shows

The 2024-25 Clean Label Project report was specific to protein supplements, which is an important fact to note. As you’ll soon see, there are very unique and understandable reasons why the heavy metal content of a protein powder might be higher than that of another type of supplement. All the same, you’re still right to demand a protein powder that is free of heavy metals, especially because of how detrimental they can be to human health.

The Clean Label Project’s Actual Findings

Of the 160 protein powders tested — representing 83 percent of the total protein powder market and 70 different brands — 47 percent of the products tested exceeded the California Proposition 65 safety thresholds for toxic metals. 

This was concerning enough, but organic protein powders tested positive at a rate of 79 percent, and were shown to possess three times more lead and twice as much cadmium as non-organic protein powders.

Also worrisome was the fact that plant-based protein powders tested positive at a rate of 77 percent and contained three times more lead than whey-based protein products, while chocolate-flavored powders tested positive for lead 65 percent of the time and contained four times more lead than their vanilla counterparts.

Prop 65 Explained

California Prop 65 was established in 1986 as the Safe Drinking Water and Toxic Enforcement Act. Aside from forbidding California businesses from knowingly discharging certain cancer-causing chemicals into the drinking water, it also requires businesses to provide warnings about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm.

It is important to note that contaminants found in protein powder  aren’t necessarily present because of direct malfeasance or carelessness on the part of the manufacturer. According to the CLP, the two primary sources of contaminants in protein powders are the contaminated soils where ingredients are grown and the packaging they are stored in.  

Specifically, heavy metals enter the environment through natural processes like volcanic eruptions, weathering of rocks, and soil erosion. Over time, they accumulate in air, water, and soil, where they can make their way into plants, animals, and eventually into human food sources. Therefore, while heavy metals are negative contributors to human health, their presence is attributable to processes that have nothing to do with human intervention.

Because authorities like the Food and Drug Administration have established that there is “no known safe level of exposure to lead,” the threshold for tolerability of lead in food is set at a very conservative level by Prop 65, which means that levels of lead that are explainable through natural processes are likely to get flagged as harmful during testing.

Banned-Substance Risk: What Athletes Need to Know

Beyond concerns about the presence of heavy metals and toxic chemicals lingering inside of protein powders, there are other substances that may catch unwary athletes off guard, cause them to face performance bans and restrictions, and unfairly damage their reputations.

Real Risks of Unintentional Enhancement

The National Collegiate Athletic Association (NCAA), and the World Anti Doping Agency (WADA) make it a common practice to caution athletes about supplement contamination for multiple reasons that have nothing to do with the aim to eliminate the ingestion of harmful contaminants like heavy metals and toxic chemicals.

Contamination of a very different sort is able to jeopardize the eligibility of athletes to engage in sports activities, potentially stripping them of honors, endorsements, scholarships, and prize money.

The crux of the matter is that athletes are incentivized to acquire an unfair competitive advantage if they can get away with it, which makes it reasonable to believe that any banned substance that an athlete tests positive for was taken with the athlete’s knowledge. Yet, this is not always the case.

For the sake of distancing themselves from competitors, supplement-makers also have a temptation to sneak banned substances into their formulations, which can positively boost the athletic performance of those who take them. 

This unethical practice can cause athletes who test positive for those substances to be treated with a presumption of guilt even if they had no reasons to believe that those banned ingredients might be present in their protein powder, creatine, preworkout, or any other performance-booster or recovery aid. 

Second, many supplement-makers manufacture and sell supplements to the public that are banned by the NCAA and WADA. Because of this concurrent production, cross-contamination within a factory can cause a banned substance to materialize within a supplement that it has no business being found in.

Documented Cases of Unintended Enhancement

A comprehensive data analysis of instances where athletes were found to have violated anti-doping rules indicates that between 4 and 19 percent of violations did not result in sanctions due to exonerations of the athletes, and acknowledged dietary supplement contamination was one of the common reasons for the reduction or elimination of an athlete sanction. (1)

Even in the relatively early stages of supplementation, the risks of unintentionally consuming a contaminated supplement were extraordinarily high. For example, an international study performed between 2001 and 2002 on 634 nutritional supplements sold across 13 different countries showed that about 15 percent of the nonhormonal nutritional supplements were contaminated with anabolic-androgenic steroids. (2)

Many years later, in March 2015, the urine samples of 11 Bulgarian weightlifters training for the European Championships tested positive for stanozolol. The positive tests were traced to a supplement called Trybest, and an analysis of the product revealed the presence of unlabeled stanozolol at amounts of 1.7–4.2 µg per capsule. Despite being unaware of the steroid’s presence, the athletes were sanctioned as they “should have been aware of the risk” associated with dietary supplements. (3)

While the aforementioned examples may have been intentional on the part of the manufacturers, some positive tests may be owed to mistakes made in the laboratory. In 2009, a growth-hormone-releasing peptide capable of producing pharmaceutical effects was detected in two different dietary supplements, but presented in an amino acid sequence and chemical structure that was not in line with their promotion. It was later deduced that other unlabeled products contaminated or adulterated with GHRPs were being sold. (4)

Valuable Certifications for Athletes to Search For

Originally known as the National Sanitation Foundation when it was founded in 1944, the organization adopted a broader focus on health and rebranded simply as NSF in 1990. 

The NSF’s “Certified for Sport” independent third-party certification program has either been adopted or recommended by more than a dozen major sports and fitness organizations.  According to NSF, the “Certified for Sport” mark verifies that a product does not contain “unsafe levels of contaminants, prohibited substances or masking agents, and that what is on the label matches what is in the product.”

Similarly, the Informed Sport certification has been adopted to guarantee the adherence of supplement manufacturers and their products both before and after the initial approval process. Once a supplements manufacturing process is reviewed and approved, and a sample has been decreed to be contaminant-free, the verified supplement is subjected to regular blind testing in order to ensure that the product remains in compliance with the Informed certification requirements.

How to Vet a Protein Powder Brand

In the end, your body will be forced to contend with every ingredient used in the composition of your preferred protein powder. This includes everything from the protein that your body is craving to the ingredients that are added to make it more palatable, to harmful metals and chemicals that can compromise your long-term health, to banned substances that might improve your training at the cost of your athletic eligibility.

With this in mind, here is a set of steps you can follow to ensure that your protein powder is not only free of harmful ingredients, but also bereft of substances that are unaccounted for on the label. 

Certifications to Look For

The first thing you should look for on your protein powder is certifications that verify that its contents are contaminant-free, and also authenticated. The aforementioned NSF “Certified for Sport” and Informed Sport certifications are a welcome sight, and another trusted mark is that of the United States Pharmacopeia (USP).

Along with requiring products to undergo similar tests to ensure that they do not contain undesired contaminants, the USP Verified mark also adorns supplements that will break down and dissolve within a practical timeframe so that their nutrients can be properly absorbed by the body as advertised. 

A Certificate of Analysis Walkthrough

The most helpful document that a supplement-maker can present you with for verifying the cleanliness of its products is a certificate of analysis from an independent testing authority. 

The first matter that a thorough certificate of analysis should put to rest is the task of authenticating the macronutrient and caloric content on the container. This is an important step, because processes like nitrogen spiking can cause protein powders to test positive for higher levels of protein than they actually contain. 

Second, a helpful COA will also reveal the levels of lead, mercury, arsenic, cadmium, and other toxic metals that may be present in the protein powder, along with undesirable microbes like yeast or salmonella.

Obvious Red Flags

The most obvious signs of a potentially harmful supplement are exactly what you would expect them to be in cases where the manufacturer either wants to hide the fact that their supplements are unclean, or doesn’t want to face the truth that they might be. 

While full transparency about product cleanliness is not yet the industry standard that Transparent Labs would like it to be, the fact remains that the simplest way to prove a supplement’s purity is to post a certificate of analysis that confirms the presence of every ingredient that’s supposed to be there, and the absence of everything that isn’t. 

In lieu of a certificate of analysis, one or more certifications from reputable institutions demonstrates that the product has undergone some degree of testing for purity and quality. The key here is to look for reputable tests, because some protein powders are labeled as “WADA certified” or “USADA certified,” when neither of these organizations performs independent supplement testing.

Finally, you’ll want to steer clear of supplements that use vague language about cleanliness without anything to back it up. Because the use of the word “clean” is unregulated, supplement-makers are free to use it with impunity. Consequently, unless the word “clean” is backed by some form of third-party testing that is capable of granting it some validity, it is simply a buzzword, and more often than not, a misleading one.

The Transparent Labs Clean Standard

The Transparent Labs team views third-party testing and the publishing of COAs as “table stakes.” In other words, if you’re going to make a claim that your supplement is clean, you need to be willing to display your “cleanliness” in an open and transparent way.

To this end, we display all of our third-party certifications on our products’ labels, and also on our website. In addition, we take things one step further by displaying all of our COAs alongside their associated products so that there is zero ambiguity about the purity of our products, and the veracity of our ingredient claims.

Of course, we also take things one step further by offering products with all-natural ingredients, and no artificial sweeteners, colors, or preservatives. This way, when you consider the information in its totality, you can be supremely confident that what you’re putting in your body has achieved the highest level of purity that is possible for any nutritional supplement to attain.Preserving Protein Purity

The presence of heavy metals and other toxic chemicals in your protein powder poses an ever present threat to you if you continue to purchase supplements blindly. Fortunately, you are now armed with the means to prevent yourself from being exposed to the pernicious effects of these unwanted ingredients. 

As long as you confirm the cleanliness of your protein powder through a certificate of analysis, or other certifying marks of reputable third-party authenticators, you can be comforted by the knowledge that your protein powder is clean, and therefore, so is your body.

Sources:

1. Walpurgis K, Thomas A, Geyer H, Mareck U, Thevis M. Dietary Supplement and Food Contaminations and Their Implications for Doping Controls. Foods. 2020 Jul 27;9(8):1012. doi: 10.3390/foods9081012. PMID: 32727139; PMCID: PMC7466328.

2. Geyer H, Parr MK, Koehler K, Mareck U, Schänzer W, Thevis M. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spectrom. 2008 Jul;43(7):892-902. doi: 10.1002/jms.1452. PMID: 18563865.

3. Walpurgis K, Thomas A, Geyer H, Mareck U, Thevis M. Dietary Supplement and Food Contaminations and Their Implications for Doping Controls. Foods. 2020 Jul 27;9(8):1012. doi: 10.3390/foods9081012. PMID: 32727139; PMCID: PMC7466328.

4. Hartman ML, Farello G, Pezzoli SS, Thorner MO. Oral administration of growth hormone (GH)-releasing peptide stimulates GH secretion in normal men. J Clin Endocrinol Metab. 1992 Jun;74(6):1378-84. doi: 10.1210/jcem.74.6.1592884. PMID: 1592884.