Protein powder and heavy metals: the certification everyone checks does not test for them
Last reviewed 2026-08-29. Every figure below was read from the certifier's own listing or report on that date, and each links its source.
The certification most people check does not test for heavy metals. That is the short answer, and it surprises nearly everyone who has been told to look for an NSF or Informed Sport mark before buying protein powder.
What those programmes are for
NSF Certified for Sport, Informed Sport and Informed Choice are banned-substance programmes. They exist because an athlete can fail a drugs test over a contaminated supplement, so lots are screened for substances prohibited in sport and the manufacturing site is audited. That is a demanding thing to pass.
It is not a contaminant panel. We read every field an NSF Certified for Sport listing publishes: brand, country of sale, product type, free-of claims, the lot numbers covered, product form, flavour, package size, serving size and the macros. There is no arsenic figure, no cadmium figure, no lead figure — not hidden, simply not part of what the listing reports. USP Verified is a genuine independent programme too, and it publishes a pass/fail mark rather than numbers, so it cannot answer the question either.
If you want to know what is in your protein powder besides protein, a banned-substance mark is the wrong document to be reading. It answers a different question, and answers it well.
What a report with actual numbers looks like
The reports we found that do publish heavy-metal results come from iHerb's iTested programme — the retailer commissioning an independent laboratory (Eurofins, on all three) for its own house brand. A weaker arrangement than an independent certifier, and a more informative document. That is an awkward combination and worth saying plainly rather than tidying away.
Three California Gold Nutrition whey isolate SKUs, each report keyed to the product code printed on its own iHerb page:
| Product — code | Lot | Arsenic | Cadmium | Lead | Mercury |
|---|---|---|---|---|---|
| Sport, Whey Protein Isolate, Unflavoured — CGN-01167 | 2404939 | <0.001 mcg | <0.005 mcg | 0.008 mcg | <0.005 mcg |
| Sport, Whey Protein Isolate, Unflavoured — CGN-01064 | 2411601 | <0.0100 ppm | <0.00500 ppm | <0.00500 ppm | <0.00500 ppm |
| Sport, Whey Protein Isolate, Dark Chocolate — CGN-01202 | 2312026 | <0.010 mcg/g | 0.021 mcg/g | 0.013 mcg/g | <0.005 mcg/g |
Figures exactly as printed on each report; every product name links the report itself.
Three things to notice before reading anything into those numbers
- The units are not the same. One report gives mcg, one ppm, one mcg/g. Those are not interchangeable, and all three come from the same programme and the same laboratory. You cannot line the columns up and rank them — and neither can we, which is why there is no ranking on this page.
- Each covers one lot. The reports name a single lot number, and iHerb's own footer states that a reduced-frequency testing scheme is used and results may not be available for all lots. The tub you receive is probably a different lot.
- Two of the three are out of date. The dates printed on the 5 lb unflavoured and dark chocolate reports had already passed when we read them.
A figure on a report is a measurement of one lot on one day. It is not a verdict about a product, and this page will not turn it into one.
Why plant protein is the one people ask about
Rice, pea and other plant proteins are concentrated from crops, and a crop takes up what is in the soil it grew in — so cadmium, lead and arsenic are the contaminants raised about plant powders specifically. The long-running complaint about whey has instead been protein content that does not match the label, which is why this site checks the protein figure on every listing against the tub's own panel. Testing that answers the first question is much scarcer than testing that answers the second.
Among the plant products we verified against an independent listing — Garden of Life Sport, Organic Plant-Based Protein, Vanilla; Garden of Life Sport, Organic Plant-Based Protein, Chocolate — the certification is NSF Certified for Sport, so the same limitation applies: banned substances, audited site, no published contaminant figures. We found no per-lot heavy-metal report for any of them.
What you can actually do
- Stop treating a banned-substance mark as a contaminant answer. Check it for what it covers — and check that the listing describes your package size, which is where most of these claims come apart.
- Look for a per-lot report that names the metals, the method and the laboratory. Very few products have one, and that scarcity is the real finding here.
- Read the lot number and the date on any report you do find, and expect the tub in your hand to be a different lot.
Every product we checked, with its evidence and match notes.
This page restates published testing records with attribution. It makes no health, benefit or treatment claim, and says nothing about whether any product is safe or good for you. A certification record describes tested lots, not a permanent grade.
Nothing on this page earns us anything today: the iHerb links are plain untagged URLs, and no product here carries an Amazon link, for the reasons set out on the main protein page. Full disclosure.
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