Protein powder's own evidence is genuinely strong — this guide isn't about whether it works. It's about a separate question: what independent testing has found inside the scoop, why three major sources of testing don't agree with each other, and what that disagreement should and shouldn't change about how you buy it.
In October 2025, Consumer Reports tested 23 popular protein powders and ready-to-drink shakes — dairy, beef, and plant-based — purchased from major retailers over a three-month period. More than two-thirds contained more lead in a single serving than CR's own benchmark of 0.5 micrograms per day. Two products, Naked Nutrition's Vegan Mass Gainer and Huel's Black Edition, were high enough that CR's experts advised against using them at all: roughly 1,570 percent and 1,290 percent of that benchmark per serving, respectively. Three products also exceeded CR's level of concern for cadmium or inorganic arsenic.
Because "exceeds the limit" depends entirely on which limit. There is no single number here — there are several, built for different purposes, and CR's is the strictest by a wide margin.
| Standard | Daily lead limit | Status |
|---|---|---|
| Consumer Reports' level of concern | 0.5 mcg | CR's own benchmark, based on California's Prop 65 dose level; CR states its results don't constitute a Prop 65 finding |
| California Prop 65 warning threshold | 0.5 mcg | Triggers a warning label, not a sales ban |
| USP supplement standard (Chapter 2232) | 5 mcg | Voluntary — enforceable only for products that claim USP conformity |
| NSF certification limit | 10 mcg | Voluntary third-party certification standard |
| FDA interim reference level, women of childbearing age | 8.8 mcg | Not an action level; FDA has none specific to protein powder |
| FDA interim reference level, children | 2.2 mcg | Same as above |
| EU food supplement maximum | ~90 mcg* | Legally binding in the EU |
*The EU sets a concentration limit (3.0 mg per kilogram of product) rather than a daily dose. Ninety micrograms is that limit applied to a 30-gram serving, shown here for rough comparison only — it isn’t a directly equivalent measurement to the other rows.
By the stricter benchmarks, most of CR's 23 products fail. By USP's 5-microgram standard, only Naked Nutrition's Mass Gainer (7.7 mcg) and Huel's Black Edition (6.3 mcg) exceed it. No single answer to "is this safe" exists independent of which standard you're asking against — which is exactly the kind of distinction marketing rarely volunteers, in either direction.
Sometimes, yes — and it's worth checking before accepting a per-serving number at face value. Naked Nutrition's Mass Gainer carries a 315-gram serving, roughly six scoops, far larger than a standard protein powder's serving. The company argued that per gram, its product wasn't more contaminated than the others CR tested. The underlying numbers mostly support that: on a concentration basis, Naked Nutrition's product measures lower than several others CR found, including Huel's. Dose and concentration are different measurements, and a serving-size difference can make one look worse than the other without either number being wrong.
The most-cited testing says yes; the most rigorous peer-reviewed study says the difference isn't statistically significant. Both CR and the Clean Label Project found plant-based powders carrying substantially more lead on average than whey — CR's figure was roughly nine times higher. But a 2025 peer-reviewed study of 90 protein supplements on the European market, using a validated laboratory method (ICP-OES) rather than consumer-testing labs, found lead levels were actually slightly higher in animal-based products, and cadmium slightly higher in plant-based — with neither difference reaching statistical significance. That study's plant-based sample was small (13 of 90 products), which its own authors flag as a limitation. A separate Hungarian study of 22 powders found toxic elements low or undetectable across the board, describing its results as reassuring but not a quality guarantee.
"Stricter quality control...is required for safety."Journal of Food Composition and Analysis, 2025
Read plainly, the category-wide "plant is worse" claim is real in some datasets and absent in others. A specific product's own published test results are a better guide than its protein source.
It's independently conducted — using an accredited laboratory and standard analytical methods (ICP-MS) — but its full methodology and funding sources aren't public, which both the Natural Products Association and the Council for Responsible Nutrition have formally objected to, without a response. Its topline finding, that 47 percent of 160 tested products exceeded a Prop 65 threshold for at least one contaminant, is widely cited; independent researchers can't fully audit how it was reached.
Manufacturers and trade groups make a consistent, partly valid point: modern testing can detect heavy metals at parts-per-billion concentrations that occur naturally in soil, water, and plants, and detection alone doesn't establish harm. The Council for Responsible Nutrition called CR's benchmark misleading; the Natural Products Association made the same argument about the Clean Label Project's report. Several companies named in CR's testing — Vega and Momentous among them — have since reformulated or changed sourcing for the specific products tested.
Two state-level responses, with different outcomes so far. In June 2026, the Texas Attorney General opened an industry-wide investigation into protein powder makers under the state's deceptive trade practices law, citing CR's and the Clean Label Project's testing; no specific brands have been named. In California, Senate Bill 1033 — which would have required manufacturers to test for heavy metals and publicly disclose the results, co-sponsored by Consumer Reports and the Environmental Working Group — passed two Senate committees before the Senate Appropriations Committee held it in suspense. It did not advance out of the Senate. Consumer Reports has separately petitioned the FDA to set enforceable federal limits, which do not currently exist for this product category.
Most healthy adults already get enough protein from food. The federal recommendation is about 0.8 grams per kilogram of body weight — roughly 61 grams a day for a 170-pound adult — and the most recent federal survey of U.S. eating habits found that Americans of every age group already exceed it. Some groups genuinely benefit from more: older adults, pregnant women, and serious athletes in specific training contexts. That's a separate question from whether a given product is contaminated, but it's worth asking first, since the simplest way to reduce exposure to any powder's heavy metals is to need less of the powder.
Treat it the way this investigation treats every other supplement question: check the specific product, not the category. Favor brands that publish third-party contaminant testing rather than a general "quality" claim. If you use protein powder daily, or are pregnant or feeding it to a child, that's exactly the situation where a stricter benchmark is the more sensible one to apply, even though it isn't a legal requirement. And keep the two questions separate: protein powder's evidence for muscle recovery is strong and well-replicated; whether a specific bottle is clean is a different question with a different, unsettled answer.
Sources include Consumer Reports' 2025 testing, the Clean Label Project's 2024–25 category report, a peer-reviewed 2025 study in the Journal of Food Composition and Analysis, FDA and USP standards documentation, and reporting on subsequent state regulatory action. See the Annotated Bibliography for full citations.