How to Reduce Your Dietary Cadmium Absorption

Cadmium and cancer- plant vs animal food
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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.

Image Credit: Julie / Flickr

  • Leonid Kalichkin

    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?

    • Joseph Gonzales R.D.

      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.

      • ron

        I take a zinc lozenge If I have a cold and sneezing a lot and several a day. Really helps a lot. Any issues with that?

        • Joseph Gonzales R.D.

          Not in my book. That seems totally fine!

      • Nisha

        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.

        • Shaylen Snarski

          What are the dangers of tea tree oil in the mouth that you’ve heard about? I haven’t heard anything about this.

      • Leonid Kalichkin

        http://www.nature.com/nature/journal/v510/n7503/full/nature13179.html

        Seems like dependence on supplements is a tough reality of our modern time. CO2 is rising, zinc concentrations in crops are declining. I guess it’s safe to say we all should take zinc supplements and get used to it, because, sooner or later, we will have to.

        • Shaylen Snarski

          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.

        • Shaylen Snarski

          Not if we stop destroying the earth.

  • Leslie

    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.

    • Julie

      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

      • ron

        Is there even a safe cocoa powder where you only have it in a smoothie once a week? Would cocoa nibs be better mixed in your blender?

        • Julie

          Yes–your safest bet is with cacao nibs, which are usually lower in cadmium than cocoa powder.
          “The only cacao products found to have lower concentrations of cadmium were cacao nibs. Essential Living Foods, Earth Circle Organics and Health Ranger Select brands of cacao nibs all showed relatively low numbers of cadmium.”

          You can get the results for 9 cocoa powders here http://labs.naturalnews.com/heavy-metals-chart-Superfoods-Cacao.html

    • Joseph Gonzales R.D.

      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?

      • Leslie

        Thanks.

        Dr. Mcdougall feels that both organic and conventional greens should be a concern, as far as heavy metals, when eating a lots of these green plants.

        https://www.drmcdougall.com/2015/08/31/broccoli-and-kale-taste-bitter/

      • Leslie

        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.

        • john

          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 …

          • ron

            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%

      • http://www.eatandbeatcancer.com/ Harriet Sugar Miller

        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?

  • Annemarie

    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.

    • Leonid Kalichkin

      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.

      • MishaBlues

        It looks like Magnitogorsk, where I was born :(

  • Craig

    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?

  • alef1

    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.)

    • Joseph Gonzales R.D.

      I wrote about kale and toxicity in this post. Do you mind seeing if this helps answer your question?

  • Anthony

    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…