Cadmium in Supplements: Sources and Limits

Quick answer

Cadmium is a metal that plants take up from soil, so it can turn up in plant ingredients, cocoa, seaweed and some mineral supplements such as zinc. The body clears it slowly. California's Proposition 65 safe harbor for cadmium by mouth is 4.1 µg a day, and FDA uses a reference range based on body weight.^1,2,3

Key facts

FDA's toxicological reference value for cadmium is 0.21 to 0.36 µg per kg of body weight a day, based on its effects on bone and kidneys.¹
In seven zinc supplements, cadmium per 15 mg of zinc varied more than 37 fold, from 0.039 to 1.46 µg.²
In U.S. cocoa products, cadmium rose with the share of cocoa solids and was higher in products from Latin America than from Africa.⁴
For smokers, smoking is the main source of cadmium exposure, according to FDA.¹
Codex maximum levels for cadmium in dark chocolates range from 0.7 to 0.9 mg/kg.¹

How cadmium gets into supplements

Soil cadmium depends on local geology and on human activity, including some phosphate fertilizers, smelting, mining and burning fossil fuels. Plants absorb it, and animals that eat them pass it on.¹

Cocoa is a well documented example. FDA scientists found cadmium from 0.004 to 3.15 mg/kg in cocoa powder and chocolate sold in the U.S., so cocoa flavored powders are worth asking about.⁴

Mineral supplements can contain it too. One analysis detected cadmium in all seven zinc supplements tested, with the least in zinc gluconate. Seaweed is another source FDA has analyzed.^1,2

Limits and benchmarks

Cadmium benchmarks^1,3
Benchmark	Amount	Set by
Toxicological reference value	0.21 to 0.36 µg per kg of body weight a day	FDA
The same range for a 70 kg adult	About 15 to 25 µg a day	Worked out from FDA's range
Proposition 65 maximum allowable dose level, by mouth	4.1 µg a day	California OEHHA
Bottled water limit	5 ppb	FDA

FDA uses its reference range when cadmium turns up in a food, to decide whether action is needed. California's figure is a warning threshold: below it, a product sold in the state needs no Proposition 65 warning for cadmium.^1,3

To compare a lab result, multiply the cadmium per gram by the grams in your daily serving and set the total beside these numbers.⁵

Health effects

The body removes cadmium slowly, so years of low exposure can build up in the kidneys, liver and other organs. FDA lists bone demineralization, kidney and reproductive dysfunction, cardiovascular disease and diabetes among the effects linked to prolonged exposure.¹

Proposition 65 lists cadmium for developmental and male reproductive harm and as a carcinogen. California's rules count cadmium as posing no significant cancer risk when swallowed, so the oral benchmark is the 4.1 µg reproductive level.^3,5

Food or drink with cadmium at levels rarely seen can cause stomach irritation, cramps, nausea, vomiting and diarrhea.¹

Questions people ask

Why is there cadmium in zinc supplements?

Zinc ingredients can carry small amounts of cadmium, and how much depends on the product. In one analysis, products using zinc gluconate had the least.²

Is cocoa a big source of cadmium?

For most people, no. FDA cites a 2021 World Health Organization conclusion that cocoa products supplied a minor share of dietary cadmium, about 0.1% to 9.4%, even where people eat a lot of them.¹

How do I check a cadmium result against FDA's range?

Multiply your body weight in kilograms by 0.21 and by 0.36 to get FDA's range in micrograms a day, then see how much of it your daily serving uses. A supplement is only one source among many.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.