Zinc Supplements and Cadmium Contamination

After posting the article Cadmium Levels in Vegans, Zinc Supplements and Alzheimer’s Disease, Ginny Messina let me know that there is a concern about cadmium contamination of zinc supplements.

I researched the issue and added the following section to VeganHealth.org’s article Cadmium:

In 2001, Krone et al tested six zinc supplements from Seattle area health food stores to see if they contained cadmium (1). According to the authors, “Because the chemical properties of [zinc] and cadmium (Cd) are so similar, these two elements invariably occur together in nature.”

They found that the single zinc supplements had very low levels of cadmium whereas the multi-mineral supplements had enough that taking the RDA of zinc would provide up to 2 µg of cadmium (20% of the daily limit recommended by the US Federal Drug Administration (FDA)). It also happens that three of the supplements with low levels of cadmium were in the form of zinc gluconate whereas none of the multi-mineral preparations were the gluconate form. So, it could be that zinc gluconate is unlikely to have much cadmium or that single zinc supplements are unlikely.

According to their website, the supplement manufacturer Kirkman, from Oregon, does a rigorous job testing their supplements for contamination of cadmium and other impurities (more info). They also have an article on their site, Cadmium: A Serious Heavy Metal and Topic. They ship outside the United States.

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References

1. Krone CA, Wyse EJ, Ely JT. Cadmium in zinc-containing mineral supplements. Int J Food Sci Nutr. 2001 Jul;52(4):379-82. | link

8 Responses to “Zinc Supplements and Cadmium Contamination”

  1. Anastasia Pseiridis Says:

    Hello,
    I just received this by email. I think there is a typo.
    In the sentence “They found that the single zinc supplements had very low levels of cadmium whereas the multi-mineral supplements had enough that taking the RDA of zinc would provide up to 2 µg of zinc (20% of the daily limit recommended by the US Federal Drug Administration (FDA)).” the third “zinc” word should be “cadmium”.
    Thank you for your precious work.
    AP

  2. Marion Says:

    Jack,
    Great and timely information, as always.
    Do you think the zinc in a daily multivitamin (such as Deva’s or VegLife) is sufficient to meet the zinc intske requirements?

  3. Joel Marks Says:

    You wrote, “They found that the single zinc supplements had very low levels of cadmium whereas the multi-mineral supplements had enough that taking the RDA of zinc would provide up to 2 µg of zinc ….” Did you mean “2 µg of cadmium”?

  4. Jack Norris RD Says:

    Anastasia and Joel,

    Thanks for catching that!

  5. Jack Norris RD Says:

    Marion,

    I don’t know how much they have, but if it’s 5 mg or more then I think it’s probably enough.

  6. Arcadio Says:

    From MedlinePlus:

    “Note that many zinc products also contain another metal called cadmium. This is because zinc and cadmium are chemically similar and often occur together in nature. Exposure to high levels of cadmium over a long time can lead to kidney failure. The concentration of cadmium in zinc-containing supplements can vary as much as 37-fold. Look for zinc-gluconate products. Zinc gluconate consistently contains the lowest cadmium levels.” (http://www.nlm.nih.gov/medlineplus/druginfo/natural/982.html)

  7. Jack Norris RD Says:

    Arcadio,

    By “consistently” my guess is that they mean in the one study I highlighted in my article above. But they don’t give any references for the statement.

  8. Arturo Says:

    As with the cadmium-laden phosphate fertilizers that are spread on fields where our food is grown, the phosphate fillers added to many processed foods and supplements (not just zinc supplements) are likely to contain cadmium. The key is to stay away from phosphate additives.

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