Plant Protein Has 9x More Lead Than Whey. Here's the Data.

There is a counterintuitive fact at the bottom of every major heavy-metals study of protein powder published in the last decade: plant protein consistently tests dirtier than whey. Not by a small margin. Consumer Reports' 2024 testing found that lead levels in plant-based protein powders were on average nine times higher than dairy-based proteins and twice as high as beef-based. The Clean Label Project found the same pattern in two separate studies, six years apart. Two-thirds of plant proteins tested by Consumer Reports contained more lead per serving than the publication's experts considered safe for daily consumption. The worst offender — Naked Nutrition's Mass Gainer — tested at 7.7 micrograms of lead per serving, which is fifteen times California's Prop 65 limit and 1,570% of Consumer Reports' level of concern.

This is uncomfortable for the wellness category in general and for the plant-based wellness category in particular. The marketing pitch on plant protein has always been that it is the cleaner, healthier, more natural choice. The data says the opposite. If your selection criteria for a protein powder include heavy metals load — and after the 2024 NEJM study showing that microplastics in arterial plaque correlate with a 4.5x increase in cardiovascular events, more people are paying attention to what is in their supplements — the evidence currently points away from plant protein, not toward it.

Here is what the published data actually shows, why plants accumulate lead the way they do, which specific brands have failed which specific tests, and what the cleanest products in the category look like.

Consumer Reports, 2024: the headline numbers

Consumer Reports tested 23 protein powders and shakes in 2024 and published the results in its January 2025 issue. The testing was done in their independent laboratories using ICP-MS for heavy metals and was the largest single Consumer Reports protein powder study in over a decade.

Two-thirds of the 23 products contained more lead per serving than Consumer Reports' experts considered safe for daily consumption. The worst offenders were:

• Naked Nutrition Mass Gainer (plant-based): 7.7 micrograms of lead per serving — 1,570% of Consumer Reports' level of concern
• Huel Black Edition: 6.3 micrograms of lead per serving — 1,290% of Consumer Reports' level of concern
• Garden of Life Sport Organic Plant-Based Protein: 400-600% of Consumer Reports' level of concern
• Momentous 100% Plant Protein: 400-600% of Consumer Reports' level of concern

The lowest-contamination products were both whey-based:

• Clean Simple Eats (whey): 0.21 micrograms of lead per serving — 42% of the level of concern
• Walmart Equate (whey): 0.27 micrograms per serving — 55% of the level of concern

The pattern was unambiguous. Lead levels in plant-based products were on average nine times higher than dairy-based and twice as high as beef-based. The single highest-lead product was a plant-based mass gainer from a brand that markets itself on minimal ingredient lists. The single lowest-lead product was a whey from a small brand. The biggest mass-market store-brand whey came in second-cleanest. The data does not respect the marketing.

Clean Label Project, 2018 and 2024-2025

The Clean Label Project is a Denver-based nonprofit that uses Ellipse Analytics, an independent ICP-MS laboratory, to test top-selling consumer products. They have run two major protein powder studies, six years apart, and the results have been remarkably consistent.

The 2018 study tested 134 top-selling protein powders. Forty percent had elevated heavy metals. Virtually all 134 products contained detectable levels of at least one heavy metal. Fifty-five percent tested positive for BPA. The most striking finding was about organic versus non-organic: certified organic protein powders were twice as likely as non-organic to contain heavy metals. Approximately 75% of plant-based protein powders had measurable lead, and plant-based proteins contained on average twice the lead per serving compared to other types. No egg-based protein powders in the study contained lead.

The 2024-2025 study ("Protein Study 2.0") tested 165 products from 70 brands, generating 35,862 individual data points. Forty-seven percent of products exceeded at least one federal or state safety threshold (most often California Prop 65's 0.5 mcg/day lead limit). Twenty-one percent of samples exceeded twice the Prop 65 level. Plant-based powders had three times more lead than whey-based; chocolate had four times more lead than vanilla; organic showed higher heavy metal levels than non-organic — the same organic-is-dirtier finding from 2018, replicated.

There are valid criticisms of the Clean Label Project's methodology. The studies are not peer-reviewed. The full testing protocols are not publicly disclosed. Critics correctly note that California Prop 65 levels (0.5 mcg/day for lead) are 25 times stricter than the FDA's interim reference level for adults (12.5 mcg/day), and that using Prop 65 as the threshold inflates the apparent failure rate. The Council for Responsible Nutrition pushed back hard on the 2025 release. All of those criticisms are valid as far as they go — but they do not undo the central finding, which is that plant-based protein consistently and reproducibly tests dirtier on heavy metals than whey-based protein, in two separate studies six years apart, using independent laboratories.

Why plants bioaccumulate lead

The mechanism is straightforward. Plants absorb minerals from soil through their roots. They cannot tell the difference between calcium and lead, or between zinc and cadmium, at the chemistry level. When a plant grows in soil that contains heavy metals — from old industrial deposition, from mining runoff, from natural geological background, from organic fertilizer like bone meal or manure that contains its own contamination — the plant takes those metals up along with the nutrients and stores them in its tissues. Some plants are more efficient bioaccumulators than others. Rice is famously aggressive about both arsenic and cadmium. Pea, hemp, and soy — the three most common plant protein sources — are all efficient lead absorbers.

Whey protein comes from cow's milk. Cows graze on a much larger volume of plant material than goes into a protein serving, and the cow itself is a biological filter — heavy metals that the cow ingests are mostly excreted or stored in bone, not concentrated into milk. Milk is not a clean source in absolute terms (it has its own contamination concerns), but it is a substantially cleaner source of protein than the bulk plant material it took to grow the cow. Egg protein is similar. The animal acts as a buffer between contaminated plant tissue and the protein you eat.

Organic farming does not solve the problem and may make it worse. The 2018 Clean Label Project finding that organic products had higher heavy metal levels than non-organic was counterintuitive on first reading and held up on follow-up. The likely reason is that organic fertilizers — bone meal, animal manure, fish meal — can contain higher metal concentrations than synthetic fertilizers, and that organic farms are often on lands previously used for non-organic farming with whatever historical soil contamination came along with that. "Organic" is a process certification, not a contaminant certification.

California Prop 65: who has been caught

California's Proposition 65 has been the de facto enforcement mechanism for heavy metals in supplements for the last decade, because the FDA does not pre-approve or test supplements before sale and there are no enforceable federal limits for heavy metals in dietary supplements. Prop 65 requires businesses to warn Californians about products that expose them to chemicals known to cause cancer or reproductive harm; for lead, the threshold is 0.5 micrograms per day. Failure to warn is a violation that can be enforced by the state Attorney General or by private citizens through a 60-day notice and lawsuit.

The list of protein powder brands that have settled or faced Prop 65 enforcement over heavy metals is long:

• MyProtein (The Hut Group) — settled in September 2020, paid $198,000 for lead contamination allegations
• Vega — paid approximately $336,000 to resolve allegations from 2013 and 2018 for lead, cadmium, and other heavy metals
• Orgain Inc. — faced violations for multiple products containing lead and cadmium
• KOS — multiple products named in complaints for lead; one product also contained cadmium
• Ancient Nutrition — 29 specific products alleged to contain lead and/or cadmium

Prop 65 cases generally settle out of court with reformulation commitments, revised warnings, and financial payments. The settlements are public, the products can be matched to the brands, and the patterns are consistent: plant-based and bone-broth-derived protein products show up in the enforcement record at much higher rates than whey isolates from grass-fed dairy.

The cleanest products in the category

Among the brands that have published reasonable contaminant testing or appeared favorably in independent testing, a few stand out. We are listing them with caveats — none of these are perfect, and the testing landscape changes frequently — but they are a starting point for people who want to make a heavy-metals-aware choice.

Whey isolates from grass-fed dairy

• Clean Simple Eats (Consumer Reports' lowest-lead product in 2024 testing, 0.21 mcg/serving)
• Walmart Equate Whey (second-lowest in Consumer Reports 2024, 0.27 mcg/serving)
• AGN Roots Grass-Fed Whey Isolate — published amino acid panels and is one of the highest-scored products in our own protein review
• Transparent Labs 100% Grass-Fed Whey Protein Isolate — third-party tested, full label disclosure, no proprietary blends
• Momentous Essential Whey Protein Isolate — NSF Certified for Sport (lot-by-lot heavy metals + label accuracy testing)

Brands with NSF Certified for Sport (the strictest third-party certification)

• Momentous (whey and plant)
• Thorne
• Klean Athlete
• Garden of Life Sport (note: the standard plant version showed up as a worst-offender in Consumer Reports — the Sport line has different testing)

NSF Certified for Sport is the strictest third-party certification available for protein powder. It tests every batch for label accuracy, contaminants (heavy metals, pesticides), and 280+ banned substances. It is the only certification recognized by the USADA, MLB, NHL, NFL, PGA Tour, and LPGA. If you want a product where lead is independently verified to be below threshold on every batch — not just on the day a third-party laboratory tested a single sample — NSF Certified for Sport is the standard.

What about the FDA?

There are no enforceable federal limits on heavy metals in dietary supplements. The FDA does not pre-approve or test supplements before sale. The agency has interim reference levels for lead (12.5 mcg/day for adults, 2.2 mcg/day for children) but those are guidance, not law, and they are 25 times more permissive than California Prop 65's 0.5 mcg/day threshold. Consumer Reports has called on the FDA to set strict, enforceable limits specifically for protein powders. The FDA has not done so.

This is a meaningful regulatory gap and it is the reason California has done most of the enforcement that has happened. If you do not live in California, the only protection you have against heavy metals in your protein powder is whatever testing the brand has voluntarily commissioned and published, plus whatever enforcement Prop 65 plaintiffs get out of California courts that ends up changing the brand's nationwide formulation. That second mechanism is the reason MyProtein, Vega, Orgain, and KOS have all reformulated — California Prop 65 is the de facto national lead standard for protein powder, even though Congress and the FDA have set none.

What this means for your selection

Three things, in order of leverage:

1. If you can use whey, use whey. The pattern across every major heavy-metals study is consistent: dairy-based protein tests cleaner than plant-based by a wide margin. If you do not have an allergy or dietary restriction that requires plant protein, the heavy-metals math says whey isolate from grass-fed dairy is the lower-contamination choice. (We are aware this is uncomfortable for the plant-based wellness narrative. The data is the data.)
2. Look for NSF Certified for Sport. It is the only third-party certification that tests every batch for label accuracy, heavy metals, and banned substances. Brands that carry it are committing to lot-by-lot testing, which is meaningfully more rigorous than the once-a-year sampling most other certifications use.
3. If you need plant protein, prioritize brands that publish their own heavy-metals Certificates of Analysis. Levels and Promix are two of the better-disclosed plant brands. Naked Nutrition publishes some testing but had a Mass Gainer product that came in at 1,570% of Consumer Reports' level of concern, which is its own kind of warning sign about how much variation can exist within a brand's product line. Treat each product on its own evidence; don't assume a brand's reputation transfers across products.

And recognize what this article is not telling you. It is not telling you protein powder is unsafe — total exposure from a daily protein scoop is small compared to other sources of dietary lead, and the cumulative health effects of micro-doses of lead at the levels seen in protein powder are not well-quantified. It is also not telling you the FDA's 12.5 mcg/day adult reference level is the wrong number — there is a reasonable scientific case that Prop 65's 0.5 mcg/day is too strict for adults. What it is telling you is that within the protein category, the heavy-metals data has a consistent pattern: plant is dirtier than animal, organic is dirtier than non-organic, chocolate is dirtier than vanilla, and the market leader by category is not necessarily the cleanest by testing. If those are inputs you care about, the data gives you a starting place.