Protein powder and heavy metals: the certification everyone checks publishes no number
Last reviewed 2026-09-22 — that date covers the two NSF programme pages cited below, which were read that day. It does not cover the figures underneath them: the laboratory results were read from their own iHerb iTested reports on 2026-08-29, and the product data behind the counts on 2026-08-30. Each figure links its own source.
The certification most people check publishes no heavy-metal figure. It covers 12 of the 17 tubs tracked here and publishes no arsenic, cadmium, lead or mercury result for any of them; the retailer programme people trust less does, for 3. 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.
To be exact about it, because the distinction matters and this page used to get it wrong: NSF Certified for Sport does test for heavy metals. What it does not do is tell you the number.
What those programmes are for — and they are not the same
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. But the two marks people treat as interchangeable do not cover the same ground:
- NSF Certified for Sport tests for contaminants as well as banned substances. Its certification-process page sets out three steps, and the second — Contents Tested & Certified — lists annual laboratory testing of contaminants, naming microbiological and heavy metals, alongside residual solvents and pesticides. Banned-substance testing of production lots is a separate, third step. Its statement of what the mark means says the programme verifies products “do not contain unsafe levels of contaminants, prohibited substances or masking agents”.
- Informed Sport describes itself, on its own about page, as a testing and certification programme whose laboratory screens every batch for substances prohibited in sport. We found no contaminant or heavy-metal testing documented there, so this page makes no claim either way about what it covers beyond that.
So a Certified for Sport mark is a statement that a laboratory found no unsafe level of heavy metals in the lots it tested. It is not a statement of how much was there.
What the public record will not give you is a measurement. 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 a number for what is in your protein powder besides protein, a certification listing is the wrong document to be reading. It records that tested lots passed, which is worth having — it is just not a measurement, and no amount of reading it will produce one.
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; Thorne Plant Protein, Chocolate; Thorne Plant Protein, Vanilla — 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.
As an Amazon Associate we earn from qualifying purchases, at no extra cost to you — commission never changes a ranking or a verdict (how this site is funded).
The plant products above, if you want to look at them: Garden of Life Vanilla → Garden of Life Chocolate → Thorne Chocolate → Thorne Vanilla →
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.
Products whose certification we did check
Every one of these matched an independent certifier's own listing on brand, flavour, package size, serving size and protein per serving. The size shown is the package the certificate covers — worth checking against whatever you are actually offered, because retailers stock sizes the certificate does not always include.
- Garden of Life Sport, Certified Grass Fed Whey, Vanilla — certified at 660 g, 24 g protein a serving Amazon →
- Garden of Life Sport, Grass Fed Whey+, Vanilla — certified at 457.5 g, 20 g protein a serving Amazon →
- Garden of Life Sport, Organic Plant-Based Protein, Chocolate — certified at 912 g, 30 g protein a serving Amazon →
- Garden of Life Sport, Organic Plant-Based Protein, Vanilla — certified at 855 g, 30 g protein a serving Amazon →
- Thorne Plant Protein, Chocolate — certified at 676 g, 22 g protein a serving Amazon →
- Thorne Plant Protein, Vanilla — certified at 630 g, 22 g protein a serving Amazon →
- Thorne Whey Protein Isolate, Chocolate — certified at 906 g, 21 g protein a serving Amazon →
Some of those are affiliate links: as an Amazon Associate we earn from qualifying purchases, at no extra cost to you, and which products appear here was settled by the certifier's records before any link was attached. Full disclosure.
Is Optimum Nutrition third-party tested? works the same distinction through one brand: real Certified for Sport listings, contaminant testing included, and still no lead figure anywhere on them.
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.
Some links on this page are affiliate links: as an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Which products appear here was settled by the certifier's records before any link was attached, and products we could not verify are linked under a plainly different button. Full disclosure.
About & editorial standards · Methodology · Affiliate disclosure · Privacy · Contact
← Every protein product we checked