Plant-based proteins and "greens" powders carry a Prop 65 warning far more often than people expect. The label is real, but it doesn't automatically mean the product is dangerous — here's what it's actually telling you.
What Proposition 65 actually requires
California's Safe Drinking Water and Toxic Enforcement Act of 1986, known as Proposition 65, requires businesses to warn Californians before exposing them to any of the more than 900 chemicals the state has listed as known to cause cancer or reproductive harm — including lead, cadmium, and arsenic, all of which occur naturally in soil and can accumulate in plants used for protein powders, greens blends, and botanical supplements.
The specific number that triggers a warning
For lead, California's Maximum Allowable Dose Level (MADL) is 0.5 micrograms per day. This is a very low threshold — independent testing has found some plant-based protein powders delivering several times that amount per serving, while others test well under it. A 2024 update to California's regulations (OEHHA) now also requires companies to identify at least one specific chemical responsible for the warning, rather than using only generic language.
Why "clean" and "organic" don't guarantee an absence of the warning
Heavy metals in plant-based products usually come from the soil the plants were grown in, not from processing or contamination during manufacturing. This means an organic, minimally processed product can still carry elevated lead or cadmium simply because of where and how the underlying crop was grown — "organic" addresses pesticide use, not naturally occurring soil metals.
The gap in enforcement worth understanding
Prop 65 is enforced primarily through private lawsuits, not routine government testing. This means a product without a warning label doesn't necessarily mean it has been tested and cleared — it may simply mean no one has tested it or filed a claim yet. Reporting on the supplement industry has found companies whose products test above the Prop 65 threshold without a warning present, alongside cases where a warning appears despite consistently low test results, sometimes tied to legal settlement agreements called consent decrees.
How to evaluate a specific product
- Check independently published third-party testing (such as ConsumerLab or Clean Label Project reports) rather than relying only on the presence or absence of a Prop 65 label.
- If a Prop 65 warning is present, check which specific chemical is named, since post-2024 labels must specify at least one.
- Consider your own exposure level — occasional use carries different risk than daily long-term use, particularly for children or during pregnancy.
- Ask the manufacturer directly for a recent Certificate of Analysis (COA) showing heavy metal test results for the specific batch you're using.
What this means practically
- A Prop 65 warning on a supplement is a real, legally required disclosure — not necessarily proof the product is unsafe at typical use levels.
- Plant-based proteins and greens powders carry elevated heavy metal risk more often than animal-based or synthetic alternatives, due to how plants absorb minerals from soil.
- The absence of a warning label isn't proof of safety, given enforcement relies heavily on private lawsuits rather than routine testing.
- Independent lab testing reports are a more reliable way to compare specific products than the presence or absence of a warning label alone.
Sources
- Consumer Reports — Heavy metal testing findings in protein powders and shakes: consumerreports.org
- ConsumerLab.com — Explanation of Prop 65 warnings on supplements: consumerlab.com
Related Kibbo Tools
- Supplement Label Safety Checklist — review a product's full label and warnings before buying.