Cadmium Levels in Vegans, Zinc Supplements and Alzheimer’s Disease

Wow – my last real post was on June 27th. But I have not fallen off the face of the earth – rather, it was right around that time that a reader brought my attention to a disconcerting study from 2006 which showed vegans in the Slovak Republic to have significantly higher cadmium levels than other diets groups. This study set me off on quite a journey that led to examining the role of zinc in Alzheimer’s Disease, of all things, and ended up strengthening my suspicions that vegans might benefit from zinc supplementation. In this case, not only because vegans can sometimes have low zinc intakes, but also to help reduce any problem caused by higher cadmium and copper intakes.

I have added this information to VeganHealth.org in an article on Cadmium. The article is too long to reproduce here, so I hope you will click through and give it a read.

I was disappointed that I had not previously heard of the study from the Slovak Republic, but these days I get notifications for any studies on vegetarians or vegans that get added to PubMed, so hopefully none will eascape my notice again.

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36 Responses to “Cadmium Levels in Vegans, Zinc Supplements and Alzheimer’s Disease”

  1. Dan Says:

    Great post.

    I wonder to what extent the fact that Slovakia was a former communist state, with terrible environmental standards, heavy mining and industry, contributes to soil and plant cadmium contamination versus other countries that did not have the terrible communist record of lack of protection of the environment. For example, if mine tailings were dumped directly into lakes and rivers, this could contribute to cadmium overload. I have a friend who is both a physical chemist working in the mining industry and a Czechoslovakian whom I can ask.

  2. Andy Says:

    Makes you wonder why cadmium is higher in vegans. I would have guessed that it would be higher in the slovakian meat eaters because of how toxins tend to concentrate as you go up the food chain. Also makes you wonder about toxins that haven’t been studied, where they are concentrated, and who might be vulnerable to them. Reminds me of the findings on arsenic and brown rice, though that one affects everyone not just vegans.

  3. Jack Norris RD Says:

    Andy,

    > I would have guessed that it would be higher in the slovakian meat eaters because of how toxins tend to concentrate as you go up the food chain.

    Cadmium concentrates in the liver and kidney, and animal’s livers and kidneys are high in cadmium, but meat-eaters rarely eat those organs.

  4. Arcadio Says:

    Slovakia seems to have one of the highest levels of Cadmium pollution in Europe. (http://www.ncbi.nlm.nih.gov/pubmed/17669565)

    map showing cadmium (Cd) measured in moss: http://origin-ars.els-cdn.com/content/image/1-s2.0-S0269749112000863-gr4.jpg
    and chart http://origin-ars.els-cdn.com/content/image/1-s2.0-S0269749112000863-gr3.jpg
    (http://www.ncbi.nlm.nih.gov/pubmed/22459708)

    As far as I know Cadmium pollution is mostly caused by humans, not nature (unlike mercury pollution).

  5. Jack Norris RD Says:

    Arcadio,

    Thanks for those charts. Can you provide the url of the report they are from?

  6. ffggfhf Says:

    According to the UNDP’s Human Development Report, Slovakia is a country of “very high” development, not an “undeveloped and developing countr[y]”.

  7. Dan Says:

    I still feel that recommending supplementation of one element (zinc) to treat a biomarker representing another element (cadmium), based on observational data like this with no health outcomes whatsoever, requires a leap of faith and is more ‘kitchen chemistry’ than ‘hard science’.

    Even if the Slovak study contained hard outcomes such that vegans with higher cadmium levels had greater risks for adverse health outcomes (which it certainly didn’t), the higher cadmium levels could be an epiphenomenon, the product of reverse causality, or third-party confounding by some other, more causal variable. I think we’ve been in this situation before with many other biomarkers which did not pan out through supplementation in randomized trials (a great example is the antioxidant “vitamin A”, which turned out to actually promote lung cancer in current and former smokers despite great promise in observational data; folic acid is another great example – despite low levels strongly correlating with various cancers, the supplementation trials actually caused increased cancer rates). Basically in science and medicine we are reduced to making guesses based on weak evidence and calling it ‘certainty’. If the best data to support zinc supplementation to reduce cadmium levels comes from a journal called “Medical Hypotheses”, one can easily say “case closed” (or “case unproven” to be more frank).

  8. Dan Says:

    I found this study in PubMed:

    http://www.ncbi.nlm.nih.gov/pubmed/1550072

    After 3 months on a lacto-vegetarian diet, 16 swedes had a drop in hair cadmium levels of 24% (p<0.001). However, the investigators believe that calcium content in the diet could have been responsible for inhibiting the uptake of cadmium ("The reason for the lower hair content of cadmium after the diet shift is unclean because cereals and vegetables are major sources of cadmium
    (2). Possibly the higher intake of calcium from the lactovegetarian diet depressed cadmium absorption, as has been demonstrated in animal experiments"). Thus this study does not provide much insight on what happens to people going on a strict vegan diet.

  9. Andy Says:

    Here’s a video on cadmium in New Zealand http://www.youtube.com/watch?v=y9t4d95Ay3c

  10. Jack Norris RD Says:

    ffggfhf,

    > Slovakia is a country of “very high” development, not an “undeveloped and developing countr[y]“.

    Would you say it’s as developed as the United States, the country I was comparing it to?

  11. Andreas Says:

    I’ve read somewhere that sunflower seeds accumulate cadmium but they also contain a large quantity of other minerals which prevent the absorption of cadmium. Should we be concerned about the cadmium accumulation in soybeans? and later tofu?

  12. Jack Norris RD Says:

    Andreas,

    I wouldn’t try to avoid any plant foods just because they might have cadmium given that, overall, they might be healthier despite the cadmium. The solution to this problem, as I see it, is to make sure you don’t have iron deficiency and take care of it if you do, make sure you get plenty of calcium, and take a modest zinc supplement. That’s what I’m doing, anyway.

  13. ffggfhf Says:

    What I would personally say is irrelevant. Both the USA and Slovakia are in the same HDI category (“very high”). Your comparison between both countries must be seen in full context:
    “It is generally thought that undeveloped and developing countries have more cadmium in their soils, which means that the levels of vegans in the Slovak Republic might be higher than would be in the United States.”

  14. Jack Norris RD Says:

    ffggfhf,

    I have to tell you that of all the things you could criticize in this article on Cadmium, choosing the fact that I suggested Slovakia is less developed than the United States seems a bit bizarre. I’m sorry I offended your sensibilities.

  15. Andreas Says:

    Jack,

    http://journals.lww.com/epidem/Fulltext/2011/01001/Blood_and_Urinary_Cadmium_Concentration_of.724.aspx

    Maybe a plant based diet increases detox of heavy metals.

  16. Jack Norris RD Says:

    Andreas,

    > Maybe a plant based diet increases detox of heavy metals.

    It seems to be fairly well accepted that high blood and urine levels of cadmium are bad, not a sign of detoxing. Not to mention that time as a vegetarian was associated with higher cadmium levels in the Slovakia study.

  17. Arcadio Says:

    The link below the image links is to the study. The images are from the full text version. Only the “paid for” version will display the large images I think.(link to full text: http://www.sciencedirect.com/science/article/pii/S0269749112000863)

    from this study: “The current study confirms that environmental monitoring programmes such as the moss survey are appropriate tools for national regulatory bodies in many European countries to assess the efficiency and effectiveness of national air pollution abatement strategies for the metals Cd and Pb.”

    I think cadmium pollution is a regional problem (as the map suggests). Some plants can tolerate more heavy metals (like Cd, Pb,…) than others, and plants in general can “neutralize” (for them!) these toxic heavy metals with phytochelatins. One cannot see from the plant wether it’s high or low in cadmium (I think). And when we eat them the cadmium is “set free”.

    Until the 1960’s in a region of Japan they had many cases of “itai itai disease”, cadmium poisoning. The cadmium Cd2+ ions replaced the caclium Ca2+ ions in the bones, resulting in extremely brittle bones. The cadmium came from polluted water (industry) and via rice to humans.

    “Cadmium is highly toxic even at low doses. Some of the effects of acute cadmium exposure are flu-like symptoms, fever, chills, muscle aches. These flu-like symptoms are referred to as “The Cadmium Blues”. More serious exposure to cadmium has much more detrimental effects. Any significant amount of cadmium taken up by the body immediately poisons the liver and kidneys. Proximal Renal Tubular Dysfunction occurs when significant amounts of cadmium are ingested, meaning the kidneys lose their ability to remove acid from the blood. A side effect of this is Gout, most likely contributing to much of the pain endured by victims of Itai-itai. The kidney damage caused by cadmium is irreversible. Serious damage is also inflicted upon the bones in a victim of Itai-itai. Cadmium poisoning leads to osteomalacia (softening of the bones) and osteoporosis (loss of bone mass and weakness). In extreme cases of this a person with Itai-itai can sustain bone fractures from their body weight alone. Cadmium is also a carcinogen.”
    […]
    “With cadmium and zinc sharing an uptake pathway, the body is fooled into taking up loads of cadmium that it believes is zinc. On top of that these women probably weren’t getting enough zinc, and a zinc deficiency can lead to a 15 fold retention rate for cadmium.”
    (http://faculty.virginia.edu/metals/cases/rasnake1.html)

    Slovakia is probably QUITE developed haha (whatever that means). Note that Belgium has the highest rates in the chart above. The other study has a map that shows cadmium pollution changing over time: http://ars.els-cdn.com/content/image/1-s2.0-S026974910700303X-gr1.jpg ” The mean concentration of cadmium in moss per EMEP grid square (50 km × 50 km) for 1990 (a), 1995 (b) and 2000 (c).” (http://www.sciencedirect.com/science/article/pii/S026974910700303X)

  18. Jack Norris RD Says:

    Arcadio,

    I got a copy of the study. From what I can tell, it’s measuring how much cadmium and lead in moss correlates with what is thought to be the levels of cadmium and lead in the country’s environment, called “deposition.” It would be good to see a study that does a better job of listing how much cadmium is in the environment as I don’t have confidence in just taking the numbers from the dots in Figure 3. Or am I missing something. I admit I didn’t read the entire paper word for word — it’s a lot of statistics that I don’t follow.

  19. Arcadio Says:

    (maybe the cadmium article shouldn’t be listed under “nutrients”, as it’s not a nutrient i think)

  20. Jack Norris RD Says:

    > (maybe the cadmium article shouldn’t be listed under “nutrients”, as it’s not a nutrient i think)

    Good point! I moved it.

  21. Tyler Says:

    I found the big jump between the vegetarian and vegan groups odd, then I looked at the study to find that there were only 10 vegans in the study. With such a low number, it can easily be skewed by something else (e.g., living near a mine etc).

    Are there any reports of cadmium issues in vegetarian or vegans in developed countries that aren’t attributable to some local environmental problem?

  22. Jack Norris RD Says:

    I don’t know of any other studies on cadmium levels in vegans.

  23. Andy Says:

    I found this from 1998, which seems to be the same Slovakian researchers as the 2006 study except this one includes vegans http://www.chempap.org/file_access.php?file=52SIa477.pdf

  24. ffggfhf Says:

    Jack Norris Registered Dietitian:
    “I have to tell you that of all the things you could criticize in this article on Cadmium, choosing the fact that I suggested Slovakia is less developed than the United States seems a bit bizarre.”

    It’s not that you suggested that Slovakia is less developed than the USA, but that you suggested that Slovakia were among the “undeveloped and developing countries”, which to me seems like the stereotypical geographical ignorance of ugly Americans.

  25. Dan Says:

    I would like to ask about phytates (phytic acid, oxalic acid, etc) in legumes. I am consuming a lot of lupin beans (from Portugal) with breakfast – very high fibre, very low carb, high protein. I decided to move my supplements (iodine, vitamin D, B-complex – and DHA until it runs out) to lunch time to keep away from the phytate load. But it would be interesting to know whether phytates could help bind cadmium, as they seem to do with other minerals (calcium, iron, zinc) and vitamins (e.g. B vitamins – where they can cause pellagra in the third world) — and by binding up the cadmium, so prevent absorption of cadmium into the body.

    However, you’d have to eat a pretty rich source of phytates with every meal. Not that hard to do, as I understand they are in whole legumes, nuts, and seeds. I do worry I am leaching calcium from my diet this way. Note this is the reason people soak lentils overnight – to activate their phytases and destroy the phytates. Uncooked lentils may be viewed as semi-“toxic”.

    I believe brazil nuts have the some of the highest levels of phytates.

    Last thing about cadmium. From the Slovak article they give a nice table of what plant-based foods contain how much. Seems it is especially concentrated in grains and seed oils. Since I don’t eat any grain (particularly wheat) and no direct seed oils (other than extra virgin olive oil and tahini), I imagine my total cadmium intake would be quite low. Without a serum level of this marker, who knows? I am not going to worry too much about this issue, however, as there is just far too many nutritional constituents that catch attention in this way. Less obsession over dietary health for a hypercondriac seems better to me.

  26. Arcadio Says:

    Jack,
    I had understood that this map (top left) http://origin-ars.els-cdn.com/content/image/1-s2.0-S0269749112000863-gr4.jpg shows how high cadmium levels are in moss in one region compared to the European average level of Cd in moss. This is the text that goes with the map image (top left):
    “Fig. 4. Maps of the normalized values per country (relative to the overall European mean) of the (top left) average Cd concentration in mosses (2005/6),”
    “normalized” I had understood to mean as “somehow adjusted” I might have completely misinterpreted the gaphic. I only glanced over the studies. (do feel free to delete any of my posts, they might be misleading)

    I found this from EFSA (European Food Safety Authority). This seems to confirm what you are saying:
    “The highest cadmium concentrations were detected in the following food commodities: seaweed, fish and seafood, chocolate, and foods for special dietary uses. For most foods only a small percentage of the analysed samples (<5 %) exceeded the maximum level (ML), where specified. Up to 20 % of the samples were above the MLs for celeriac, horse meat, fish, bivalve molluscs other than oysters and cephalopods."
    […]
    "Due to their high consumption of cereals, nuts, oilseeds and pulses, vegetarians have a higher dietary exposure of up to 5.4 µg/kg b.w. per week. Regular consumers of bivalve molluscs and wild mushrooms were also found to have higher dietary exposures of 4.6 and 4.3 µg/kg b.w. per week, respectively."
    […]
    "high absorption rates common in women of reproductive age groups due to high prevalence of low and empty iron stores"
    […]
    "the CONTAM Panel established a tolerable weekly intake (TWI) for cadmium of 2.5 µg/kg b.w.
    The mean exposure for adults across Europe is close to, or slightly exceeding, the TWI of 2.5 µg/kg b.w. Subgroups such as vegetarians, children, smokers and people living in highly contaminated areas may exceed the TWI by about 2-fold. Although the risk for adverse effects on kidney function at an individual level at dietary exposures across Europe is very low, the CONTAM Panel concluded that the current exposure to Cd at the population level should be reduced."
    (http://www.efsa.europa.eu/en/efsajournal/pub/980.htm)

    Thanks for all your work!

  27. Jack Norris RD Says:

    Arcadio,

    Thanks for the follow-up. Yes, I realize that map shows the distribution in moss, but from reading the paper I got the impression that moss doesn’t necessarily give a good representation of overall cadmium in the environment. In the case of Slovakia, however, the moss matched the distribution perfectly (but it didn’t for other countries).

  28. Joe Says:

    Since this is a vegan-oriented health blog, I thought I’d share that Jarrow Formulas states on their website that their zinc capsules consist of “hydroxypropylmethylcellulose” (http://www.jarrow.com/product/431/Zinc_Balance ). This seems to be a plant-based product but I’m not sure. Another website selling it said that this supplement is vegan. It seemed cheaper than any other vegan alternatives I found so I ordered some bottles. Just got them and see that the actual ingredients list says “Capsule consists of gelatin.” Gelatin is definitely an animal bi-product, but I wonder whether it is a mislabeling of the actual ingredient.

  29. Arcadio Says:

    Jack,
    do you happen to know whether it makes any difference what form the zinc is in in a supplement, e.g. “zinc gluconate” or “zinc sulfate”..? Thanks!

  30. Jack Norris RD Says:

    Arcadio,

    > do you happen to know whether it makes any difference what form the zinc is in in a supplement, e.g. “zinc gluconate” or “zinc sulfate”..?

    I don’t.

  31. Arcadio Says:

    http://www.ncbi.nlm.nih.gov/pubmed/1550072

    In this study from 1992 a switch from a mixed to a lactovegetarian diet led to a 24% drop in cadmium levels measured in hair samples.

  32. mpe Says:

    Hi
    Maybe you want add to the Zinc article the info you have on
    Zinc sulfate here (http://jacknorrisrd.com/zinc-supplements-which-are-absorbed-best/)
    or if there is any research?
    Thanks!

  33. Gregg Says:

    I just happened to find this article while researching cadmium and arsenic in vegans. I recently had a whole blood test for toxic metals performed, and both (arsenic and cadmium) are on the high side. I’ve only been vegan for about 2 years, and since I didn’t have a baseline at the time I switched, I can’t be 100% sure it’s due to the plant based diet. My zinc level also comes in a bit low, along with omega 3. Despite eating foods like flax, chia, etc., I may need to supplement. I already take B12 and D, and if I’m going to add zinc and DHA/EPA, I have to question whether or not an entirely plant based diet is right.

  34. Jack Norris RD Says:

    Gregg,

    The last I reviewed the literature, there was no easy way to tell what someone’s zinc status is apart from exhibiting deficiency symptoms. If you don’t get colds easily or cracks in your skin around orifices, there’s no reason to supplement with zinc, in my opinion. It’s also not clear that the average, lower DHA levels in vegans is associated with poor health, though if you’re especially low I’d recommend 200 – 300 mg every 2-3 days to match what fish eaters would typical eat.

  35. Gregg Says:

    I haven’t noticed anything along those lines, but I was curious if you’ve reviewed this article about omega 3. I found it after something I saw in a youtube video by Dr. Greger. It’s the reason I was thinking about supplementing with some algae omega.

    http://www.neurology.org/content/78/9/658.abstract

  36. Jack Norris RD Says:

    Gregg,

    I’ll get a copy of that article and take a look.

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