Cadmium and cancer- plant vs animal food

Image Credit: Julie / Flickr. This image has been modified.

How to Reduce Your Dietary Cadmium Absorption

Cadmium is known as a highly toxic metal that represents a major hazard to human health. It sticks around in our body for decades because our body has no efficient way to get rid of it and may contribute to a variety of illnesses, including heart disease, cancer, and diabetes.

Most recently, data suggests that cadmium exposure may impair cognitive performance even at levels once thought to be safe. Recent studies also suggest that cadmium exposure may produce other adverse health effects at lower exposure levels than previously predicted, including increased risk of hormonal cancers. For example, researchers on Long Island estimated that as much as a third of breast cancer in the U.S. might be associated with elevated cadmium levels.

Inhalation of cigarette smoke is one of the major routes for human exposure to cadmium. Seafood consumption is another route of human exposure. The highest levels, though, are found in organ meats. But how many horse kidneys do people eat? Since people eat so few organs, grains and vegetables actually end up contributing the largest amount to our collective diets.

However, don’t drop the salad from the menu yet.

Whole grains and vegetables are among the major dietary sources of fiber, phytoestrogens, and antioxidants that may protect against breast cancer. Indeed, even though the risk of breast cancer goes up as women consume more and more cadmium, and even though on paper most cadmium comes from grains and vegetables, breast cancer risk goes down the more and more whole grains and vegetables women eat. So, are animal sources of cadmium somehow worse, or do the benefits of plant foods just overwhelm any adverse effects of the cadmium?

A study out of the Journal of the Medical Association of Thailand, highlighted in my video, Cadmium and Cancer: Plant vs. Animal Foods, may have helped solve the mystery. It’s not what we eat; it’s what we absorb.

Cadmium bioavailability from animal-based foods may be higher than that from vegetable-based foods. There appears to be something in plants that inhibits cadmium absorption. In fact, researchers found when they added kale to boiled pig kidneys, they could cut down on the toxic exposure. Just one tablespoon of pig kidney, and we may exceed the daily safety limit—unless we add kale, in which case we could eat a whole quarter cup. The pronounced effects of the inhibitory factors in kale point out, as the researchers note, “the importance of vegetable foods in terms of prevention of health hazard from [cadmium] ingested as mixed diets in a real situation.”

Researchers have concluded: “Even if a vegetarian diet contains more lead and cadmium than a mixed diet, it is not certain that it will give rise to higher uptake of the metals, because the absorption of lead and cadmium is inhibited by plant components such as fiber and phytate.” Having whole grains in our stomach up to three hours before we swallow lead can eliminate 90% of absorption, thought to be due to phytates in whole grains, nuts, and beans grabbing onto it.

So, vegetarians may have lower levels of lead and cadmium even though they have higher intakes.

In fact, there is a significant decrease in the hair concentrations of lead and cadmium after the change from an omnivorous to a vegetarian diet, indicating a lower absorption of the metals. Researchers took folks eating a standard Swedish diet and put them on a vegetarian diet. The vegetarians were encouraged to eat lots of whole, unrefined plant foods, with no meat, poultry, fish, and eggs. Junk food was also discouraged. Within three months on a vegetarian diet, their levels significantly dropped, and stayed down for the rest of the year-long experiment. The researchers came back three years later, three years after the subjects stopped eating vegetarian, and found that their levels of mercury, cadmium, and lead had shot back up.

Since the cadmium in plants is based on the cadmium in soil, plant-eaters that live in a really polluted area like Slovakia, which has some of the highest levels, thanks to the chemical and smelting industries, can indeed build up higher cadmium levels, especially if they eat lots of plants. It’s interesting that, “in spite of the significantly higher blood cadmium concentration as a consequence of a greater cadmium intake from polluted plants, all the antioxidants in those same plants were found to help inhibit the harmful effects of higher free radical production caused by the cadmium exposure.” Still, though, in highly polluted areas, it might be an especially good idea not to smoke, or eat too much seafood, or organ meats. But even if we live in the Slovak Republic’s “black triangle of pollution,” the benefits of whole plant foods would outweigh the risks. For people in highly polluted areas, zinc supplements may decrease cadmium absorption, but I’d recommend against multi-mineral supplements, as they have been found to be contaminated with cadmium itself.

There are other toxins in cigarette smoke also found in food. See:

Toxic metals have also been found in dietary supplements. See for example, Get the Lead Out and Heavy Metals in Protein Powder Supplements.

Mercury is also a serious problem. See:

More on pollution in seafood can be found in:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.


29 responses to “How to Reduce Your Dietary Cadmium Absorption

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  1. Hi, Docs. I know about dangers of calcium supplementation, but what about zinc? Where’s the balance of evidence? We know that thymus shrinks as we age, but zinc has shown to stimulate regrowth of thymus in mice ( http://www.ncbi.nlm.nih.gov/pubmed/8453784 ). If we defeat heart disease and cancer, respiratory diseases could be the most common culprit of death at old age. It seems that we are all prone to zinc deficiency, especially plant-based dieters and the elderly. Zinc supplementation seems to boost immunity and help fighting common cold. I know that you encourage getting nutrients from whole food, but what if our soil is deficient in zinc just like it is with iodine and selenium?




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    1. Good points about staying on top of our zinc requirements. It’s hard to take mouse models for face value, so we never like to really depend on them. Human trials are what we need. Here’s a great video about zinc requirements and ways to enhance zinc absorption. If the soil is depleted and you’re certain you are not getting enough from foods perhaps a supplement could help.




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      1. Any information on Dr. Gregor’s stance on tea tree oil used in “health food store”dental floss and toothpicks – whole foods and stores like that? I have come across warnings on tea tree oil in the mouth, but I assume they use low amounts in floss and other toothpastes. But their does seem to be research saying to avoid tea tree oil touching any mucous membranes.




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        1. Not if we stop destroying the earth. I worry about supplementing with minerals because they sometimes compete with each other so I worry about messing with the balance. I do have 50% dv of zinc in my multivitamin, and I did recently get a really good zinc supplement which I only take once in a while.




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  2. What plants tend to have the highest levels of cadmium?

    What grains? How would you rank barley, brown rice, white rice, wheat, millet?

    I’ve read before that chocolate can be extremely high in cadmium.

    Thanks.




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    1. Lesle, yeah unfortunately most cocoa products contain cadmium. “The bad news was that of eight cocoa powders, six failed because of excessive cadmium levels, with most having three to five times the WHO limit. Two had more than three times the California limit and one had five times the limit. And one cocoa powder that fell below the cadmium limit contained a small amount of lead, as did two other powders. Lead is another toxic metal that is regularly detected in cocoa products.” http://www.berkeleywellness.com/healthy-eating/food-safety/article/there-cadmium-your-cocoa




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    2. There are studies that Dr. Greger mentions in Cadmium and Cancer: Plant vs. Animal Foods that help answer this question. From what I see the highlighted studies are lumping vegetables and whole grains into one category, so it’s not clear what specific grains are worst. It’s true that vegetables were found to have cadmium, but interestingly they inhibit the absorption of cadmium so it’s likely not a concern. As Dr. Greger always seems to point out it’s what you absorb that really matters! We don’t need to ditch the kale and collards. This reminds me about the kale and thallium scare a few months ago.

      Re: chocolate. Yes, a few studies exist. Another user posted some helpful studies and links here and 13 others to browse thru here, if you’d like. From what I see (and from other reports like Julie’s below), there does seem to be concerns about cadmium in chocolate, but perhaps it also depends on what we absorb?




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      1. As far as chocolate, any data suggesting harmful residue from chocolate that has been treated to remove bitterness, via treating with alkali? I know that the ducting of chocolate reduces certain beneficial things, what I am more concerned about is any residue/chemicals/altered properties in the chocolate resulting from this man-made ditching process.




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        1. I like consumerlab dot com as one source for information. They have an excellent graph chart of about 22 products in their review of cocoa powders, dark chocolate, extracts, nibs, and supplements …




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          1. Yes, and most powders did not pass. So far only one I should buy is the cocoa via stick powder to get the most flavanols and low cadmium. The bars we get are either Trader Joe’s 72% and Ghiradelli 72%




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      2. Your last statement seems so important…that it depends on what we absorb. Wouldn’t vegetables with their high concentrations of chlorophyll, flavonoids, carotenoids and fiber help bind those toxins and send them down the toilet where they belong? Can you point us to any studies on that?




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  3. This has given me a lot to consider. I had hair analysis done a few years ago when the brown rice/arsenic connection was in the news. I merely had it done out of curiosity since I ate a lot of brown rice. To my surprise (and my naturopaths’) the report came back indicating I had higher than normal levels of arsenic, aluminium, lead and cadmium. I should point out I had been a plant eater (vegan) for 33 years at that point. I never smoked and had little exposure to second hand smoke. Being a teacher my work place was not a source of this heavy metal toxicity either. In particular, the cadmium results always bothered me because no one could tell me the possible source of exposure. But now after reading this and the connection to cadmium in the soil I may have the answer. My city is host to the automotive industry and at one point all three manufacturers had factories here spouting out toxic chemicals. We’re known to have one of the poorest air qualities in the country and also higher than average cancer rates. It’s not a stretch to assume what’s in the air ends up in the soil and then in the plants I’ve eaten over the past 3 decades. I hate to think my plant based diet has contributed to my cadmium load. And the question is, what do I do about it.




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    1. My city has one of the worst ecological situations in Russia. That’s what we breathe in: http://fx-commodities.ru/wp-content/uploads/2015/04/OAO-Achinskij-glinozemnyj-kombinat-2.jpg

      The wind direction is usually to the city, so our air is constantly polluted with formaldehyde and benzo[a]pyrene. Our city has one of the highest estimated cancer risks in our country which is 70% higher than accepted levels. We suffer from higher occurence of tumors, neurological disorders and respiratory diseases. Well, I hope my plant-based diet will help me a little bit.




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  4. Interesting that hair concentration of metals is now valid? I’ll have to look at pubmed for this. Medicine has denied the relevance of this for years, I thought?




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  5. Some plants – like kale, apparently can minimize the bioavailability of the toxic metal cadmium. To what extent might this generalize – or not! – to the absorption of other toxic metals found in plant foods? I particularly wonder about arsenic, such as the arsenic reported in American rice, and to what extent plants may, or may not, minimize its absorption or its bio-availability in other ways. (Some chemical compounds of toxins, for example of mercury or fluoride, seem far more toxic and reactive than other forms.)




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  6. If I may add: Cadmium and Zinc binds same protein transporters in the body. So Zinc deficiency is the highest risk to develop Cd toxicity i.e Vegetarianism. most vegetarian people are deficient in Zn since this latter is poorly present in non-animal proteins and also affected by plant anti-nutrients…




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    1. Another video shows garlic and onions promote zinc absorption. The same authors, Indian, later tested another also effective enhancer, amchur (mango) powder, often used in Indian cooking. I am curious as to what is common (sulfur?) and what other ingredients might also work (asafoetida?). As far as low zinc levels in foods, that is true for most common vitamins and minerals in Northern American vegetables and fruits. In other parts of the world, plus many natives like Native Americans, they’re used to using the whole plants, leaves, fruit, and root, yet here we often only see beets or carrots sold whole. That, plus other factors like a tendency to favor more mild tasting vegetables, would account for low levels of just about everything in food. Before I thought 30-40% of the RDA of calcium in one serving was good, but now, as with other vitamins and minerals, searching the limited info out there of once used plants, or ones still used in other continents, some now imported by immigrants and found at ethnic markets, that now I consider only moderately good and am on the search for 60-100%+ in one serving of this or that mineral or vitamin foods.




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  7. In recent lab work my cadmium level was 1.5 (normal high being 1.2). Should I worry? My neurologist suggested to lower my meat, chicken, fish, potato intake, even though I don’t each large amounts of any of those. My lead and arsenic was normal and mercury not detected.




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  8. Hi Claudia: this is Dr. Daniela Sozanski, Moderator with Nutritionfacts.org and Naturopathic Doctor in Atlanta, GA. I am thinking that your blood test results should not be ignored.
    There are several ways to go about detoxifying from heavy metals from the most complex and physician assisted which is chelation therapy, to more available protocols, such as daily detox or seasonal spring cleansing.
    Let’s look at some natural detoxifiers that you can research. Before going thru them though, I need to emphasize that following a diet rich in such compounds is recommended as a first approach, instead of supplementing.
    Dr. Sidney McDonald Baker in his excellent book “Detoxification and Healing” mentions the following (mind you, specific for Mercury detox, but also for other heavy metals): vitamin C, alpha lipoid acid (found in spinach, broccoli, tomato and green tea), zinc, selenium and Vitamin E; they are all abundant in plant food diets; there are other recommendations, but only as supplements or chemical chelation agents.
    I have used myself the early morning glass of water with the juice of one lemon, occasionally with a teaspoon of good quality olive oil as a daily mild but continuous detoxifier.
    One more thing, one article just today spoke about evidence of heavy metal detoxification through the skin, via abundant sweating. Therefore a cycle class three times a week and/or sauna may help you detoxify.
    Finally, please remember that, while in agreement that today plants may be contaminated with heavy metals, a plant based diet is recommended, also for its ability to naturally detoxify.
    Some web based references, from Dr. Jonathan Wright’s site, one of my favorites:
    http://www.faim.org/seasonal-spring-cleanse-protocol
    http://www.faim.org/help-for-flint-water-crisis-chelation-therapy
    I hope this helps. Daniela




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