Organic chicken broth is popular with paleo diet advocates, but do tests indicate the presence of the toxic heavy metal lead?
Lead Contamination in Bone Broth
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There are toxicological issues associated with production and processing of meat, issues like the presence of various toxic contaminants, from dioxins and PCBs to the cooked meat carcinogens. Carcinogenesis, the development of cancer, may be the main concern, but there are a number of other toxic responses connected with the consumption of meat products. Lead, for example, can be toxic to the nerves, gastrointestinal tract, bone marrow, and kidneys.
Where is lead found in the food supply? In general terms, the highest levels of lead, as well as arsenic and mercury, are found in fish. Sardines have the most arsenic, but tuna may have sardines beat when it comes to mercury and lead.
The problem is that fish-consumption advisories related to human health protection do not consider the fish by-products fed to farmed animals like farmed fish. If some tilapia are fed tuna by-products, they could bioaccumulate heavy metals and pass them onto us. The highest levels have been found in frozen sole fillets, averaging above the legal limit for lead.
Lead exposure has been shown to have adverse effects on nearly every organ system in the body. Symptoms of chronic exposure range from memory loss and constipation to impotence and depression. This is, all after, pretty hefty exposure, though. But we now know that blood lead levels in the range currently considered acceptable are associated with increased prevalence of gout and hyperuricemia, elevated levels of uric acid in the blood. According to the Centers for Disease Control and the World Health Organization, a blood lead level needs to be less than 25 (micrograms per deciliter) to not be elevated. And so, you’d assume that at all these values under 25, there’d be no relationship with health outcomes, but even throughout this “acceptable” range, lower lead means lower uric acid levels and lower gout risk. So, even blood lead levels 20 times below the acceptable level can be associated with increased prevalence of gout. These data suggest that there is no such thing as a “safe” level of exposure to lead.
And once it gets in the body, it tends to stay in the body. It builds up in the bones, such that it may take 30 years just to get rid of half; so, the best strategy would be to not get exposed in the first place.
If it builds up in bones, though, what about boiling bones for broth? We know bones sequester lead, and such lead can then leach from the bones; so, they figured that bone broth made from the bones of farmyard animals might carry a risk of being contaminated with lead. Who eats bone broth? Bone broth consumption is encouraged by many advocates of the paleo diet. Online, you can learn all about the benefits of bone broth, but what they don’t mention is the theoretical risk of lead contamination, or at least it was theoretical, until now. Broth made from chicken bones was found to have markedly high lead concentrations, up to a 10-fold increase in lead. In view of the dangers of lead consumption to the human body, they recommend that doctors and nutritionists take the risk of lead contamination into consideration when advising patients about bone broth diets.
But what if you only use bones from organic, free-range chickens? The researchers in the literature cited above did only use bones from organic, free-range chickens.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- E Krishnan, B Lingala, V Bhalla. Low-level lead exposure and the prevalence of gout: an observational study. Ann Intern Med. 2012 Aug 21;157(4):233-41.
- J A MOnro, R Leon, B K Puri. The risk of lead contamination in bone broth diets. Med Hypotheses. 2013 Apr;80(4):389-90.
- G Perello, R Marti-Cid, J M Llobet, J L Domingo. Effects of various cooking processes on the concentrations of arsenic, cadmium, mercury, and lead in foods. J Agric Food Chem. 2008 Dec 10;56(23):11262-9.
- S A Saidi, M S Azaza P Windmolders, J van Pelt, A El-Feki. Cytotoxicity evaluation and antioxidant enzyme expression related to heavy metals found in tuna by-products meal: An in vitro study in human and rat liver cell lines. Exp Toxicol Pathol. 2013 Nov;65(7-8):1025-33.
- P Olmedo, A Pla, A F Hernandez, F Barbier, L Ayouni, F Gil. Determination of toxic elements (mercury, cadmium, lead, tin and arsenic) in fish and shellfish samples. Risk assessment for the consumers. Environ Int. 2013 Sep;59:63-72.
- L Check, A Marteel-Parrish. The fate and behavior of persistent, bioaccumulative, and toxic (PBT) chemicals: examining lead (Pb) as a PBT metal. Rev Environ Health. 2013;28(2-3):85-96.
- Püssa T. Toxicological issues associated with production and processing of meat. Meat Sci. 2013 Dec;95(4):844-53.
Images thanks to Jessica & Lon Binder via Flickr.
There are toxicological issues associated with production and processing of meat, issues like the presence of various toxic contaminants, from dioxins and PCBs to the cooked meat carcinogens. Carcinogenesis, the development of cancer, may be the main concern, but there are a number of other toxic responses connected with the consumption of meat products. Lead, for example, can be toxic to the nerves, gastrointestinal tract, bone marrow, and kidneys.
Where is lead found in the food supply? In general terms, the highest levels of lead, as well as arsenic and mercury, are found in fish. Sardines have the most arsenic, but tuna may have sardines beat when it comes to mercury and lead.
The problem is that fish-consumption advisories related to human health protection do not consider the fish by-products fed to farmed animals like farmed fish. If some tilapia are fed tuna by-products, they could bioaccumulate heavy metals and pass them onto us. The highest levels have been found in frozen sole fillets, averaging above the legal limit for lead.
Lead exposure has been shown to have adverse effects on nearly every organ system in the body. Symptoms of chronic exposure range from memory loss and constipation to impotence and depression. This is, all after, pretty hefty exposure, though. But we now know that blood lead levels in the range currently considered acceptable are associated with increased prevalence of gout and hyperuricemia, elevated levels of uric acid in the blood. According to the Centers for Disease Control and the World Health Organization, a blood lead level needs to be less than 25 (micrograms per deciliter) to not be elevated. And so, you’d assume that at all these values under 25, there’d be no relationship with health outcomes, but even throughout this “acceptable” range, lower lead means lower uric acid levels and lower gout risk. So, even blood lead levels 20 times below the acceptable level can be associated with increased prevalence of gout. These data suggest that there is no such thing as a “safe” level of exposure to lead.
And once it gets in the body, it tends to stay in the body. It builds up in the bones, such that it may take 30 years just to get rid of half; so, the best strategy would be to not get exposed in the first place.
If it builds up in bones, though, what about boiling bones for broth? We know bones sequester lead, and such lead can then leach from the bones; so, they figured that bone broth made from the bones of farmyard animals might carry a risk of being contaminated with lead. Who eats bone broth? Bone broth consumption is encouraged by many advocates of the paleo diet. Online, you can learn all about the benefits of bone broth, but what they don’t mention is the theoretical risk of lead contamination, or at least it was theoretical, until now. Broth made from chicken bones was found to have markedly high lead concentrations, up to a 10-fold increase in lead. In view of the dangers of lead consumption to the human body, they recommend that doctors and nutritionists take the risk of lead contamination into consideration when advising patients about bone broth diets.
But what if you only use bones from organic, free-range chickens? The researchers in the literature cited above did only use bones from organic, free-range chickens.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- E Krishnan, B Lingala, V Bhalla. Low-level lead exposure and the prevalence of gout: an observational study. Ann Intern Med. 2012 Aug 21;157(4):233-41.
- J A MOnro, R Leon, B K Puri. The risk of lead contamination in bone broth diets. Med Hypotheses. 2013 Apr;80(4):389-90.
- G Perello, R Marti-Cid, J M Llobet, J L Domingo. Effects of various cooking processes on the concentrations of arsenic, cadmium, mercury, and lead in foods. J Agric Food Chem. 2008 Dec 10;56(23):11262-9.
- S A Saidi, M S Azaza P Windmolders, J van Pelt, A El-Feki. Cytotoxicity evaluation and antioxidant enzyme expression related to heavy metals found in tuna by-products meal: An in vitro study in human and rat liver cell lines. Exp Toxicol Pathol. 2013 Nov;65(7-8):1025-33.
- P Olmedo, A Pla, A F Hernandez, F Barbier, L Ayouni, F Gil. Determination of toxic elements (mercury, cadmium, lead, tin and arsenic) in fish and shellfish samples. Risk assessment for the consumers. Environ Int. 2013 Sep;59:63-72.
- L Check, A Marteel-Parrish. The fate and behavior of persistent, bioaccumulative, and toxic (PBT) chemicals: examining lead (Pb) as a PBT metal. Rev Environ Health. 2013;28(2-3):85-96.
- Püssa T. Toxicological issues associated with production and processing of meat. Meat Sci. 2013 Dec;95(4):844-53.
Images thanks to Jessica & Lon Binder via Flickr.
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Title
Lead Contamination in Bone Broth
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
For more on the paleo diet, see:
- Paleopoo: What We Can Learn from Fossilized Feces
- Paleo Diets May Negate Benefits of Exercise
- The Problem with the Paleo Diet Argument
Other products contaminated with lead include Ayurvedic supplements, protein powders, wild animals shot with lead ammunition, dairy products, and tea from China:
- Get the Lead Out
- Heavy Metals in Protein Powder Supplements
- Filled Full of Lead
- California Children Are Contaminated
- Lead Contamination of Tea
- How to Lower Lead Levels with Diet: Thiamine, Fiber, Iron, Fat, Fasting?
- How to Lower Lead Levels with Diet: Breakfast, Whole Grains, Milk, Tofu?
- The Effects of Low-Level Lead Exposure in Adults
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