Bone Broth and Lead Toxicity: Should You Be Concerned? | Chris Kresser

Bone Broth and Lead Toxicity: Should You Be Concerned?

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Are there toxic levels of led in bone broth? Vladislav Ageshin/Hemera/Thinkstock

Yesterday I became aware of a study published in the journal Medical Hypotheses called “The risk of lead contamination in bone broth diets.” (1) The authors mention that consumption of bone broth may be increasing because it is recommended by advocates of both the GAPS and Paleo diets. It’s well-established that farm animals (and humans, for that matter) can be exposed to lead via food, water, air, dust and soil, and that it progressively accumulates in bone. The researchers wanted to find out whether the bones of farm animals might sequester lead, which would then be released into broth during its preparation.

Does bone broth contain toxic levels of lead? Tweet This

To find out, they prepared chicken broth (using organic chickens) three different ways:

  • using chicken bones;
  • using cooked chicken meat without the bones;
  • using chicken skin and cartilage without the bones after the whole chicken had been cooked.

In each case the same tap water, cooking utensils, cookware and cooking time was used. They also included a fourth control preparation, where they followed the same procedure but used only tap water heated for the same length of time. The lead concentrations in the four different samples were as follows:

  • chicken-bone broth: 7.01 µg/L
  • bone broth from chicken meat (without bones): 2.3 µg/L
  • bone broth made from skin and cartilage off the bone: 9.5 µg/L
  • control (tap water): 0.89 µg/L

As you can see, the levels of lead in bone broth made from chicken bones was a little over 7x higher than the tap water, and a little over 10x higher in broth made from chicken skin and cartilage. As the authors point out, lead has “adverse medical effects on the central nervous system, peripheral nervous system, haemopoietic system, gastrointestinal tract, renal system, cardiovascular system, endocrine system and reproductive system”. In short, too much lead wreaks havoc on every system of the body.

Does this mean it’s time to quit the bone broth? Not so fast.

How Much Lead Is Safe?

The authors of the study express alarm about the “high” levels of lead found in the bone broth preparations they made. However, the US Environmental Protection Agency (EPA) has established a safety threshold of 15 parts per billion (ppb, which is equivalent to 15 µg/L) for lead in drinking water. On their page discussing lead and water, they explain that:

Most studies show that exposure to lead-contaminated water alone would not be likely to elevate blood lead levels in most adults, even exposure to water with a lead content close to the Environmental Protection Agency’s (EPA’s) “action level” for lead of 15 parts per billion (ppb). Risk will vary, however, depending upon the individual, the circumstances, and the amount of water consumed. For example, infants who drink formula prepared with lead-contaminated water may be at a higher risk because of the large volume of water they consume relative to their body size.

If drinking water consistently throughout the day with lead levels of 15 µg/L (ppb) does not pose a problem for human adults (and children with the exception of infants drinking formula), then why would drinking 2-3 cups of bone broth with lead levels of 9.5 µ/L pose a problem? I don’t think it would.

That might be the end of the argument right there. But there are additional factors to consider that may make lead in homemade chicken broth even less of a concern.

The Importance of Nutrient Synergy

There’s no doubt that it’s smart to minimize exposure to toxins as much as possible. But in an environment where toxins are found in foods that also contain beneficial nutrients, we must always balance the benefits of those nutrients against the potential harms of the toxins. What’s more, some nutrients protect against the harmful effects of toxins.

For example, I’ve written on the blog and talked on my podcast about how selenium protects against mercury toxicity in fish. More specifically, the reason mercury is toxic is that it damages selenium-dependent enzymes that play a crucial role in protecting us from oxidative damage. This is why you’ve heard so much publicity about the dangers of consuming fish with mercury. However, what these reports neglected to consider is that if a food you consume contains more selenium than mercury, or if background selenium intake is high, mercury won’t be able to destroy all of your selenoenzymes and you’ll be protected from its toxic effects.

As it turns out, certain nutrients like calcium, iron, vitamin D, vitamin C and thiamin (B1) have a similar protective effect against lead toxicity. These nutrients are abundant in Paleo and GAPS diets, and in the case of calcium, abundant in bone broth itself. Let’s take a closer look at how two of these nutrients, calcium and iron, protect against lead toxicity.

Calcium

Both animal and human studies have shown that low calcium intake increases the risk of lead toxicity. In one rat study, researchers found that rats ingesting a low calcium diet had blood-lead concentrations four times higher than rats on a normal calcium diet, although the quantities of lead ingested were equal. The mechanisms by which calcium protects against lead toxicity involve complex interactions among lead, dietary calcium, intestinal calcium binding proteins and vitamin D, especially 1,25 D (the active form). (2) In fact, the interaction between calcium and lead is quite similar to that of selenium and mercury: one of the ways lead causes harm is by interfering with the beneficial effects of calcium. Lead is known to mimic calcium in biological systems or to alter calcium-mediated cellular responses, compete with calcium in enzyme systems, impair calcium metabolism, or inhibit 1,25-D-mediated regulation of calcium metabolism. (3) Calcium has also been shown to reduce the absorption of lead in the gastrointestinal tract. (4)

Iron

Studies have also shown that susceptibility to lead toxicity is influenced by nutritional iron status. A study in the early 70s found that rodents fed an iron-deficient diet experienced increased susceptibility to lead toxicity. In humans, low iron status of adults has been reported to increase gastrointestinal absorption of lead. (5) As is the case with the lead-calcium and mercury-selenium interactions, lead has been shown to interfere with iron’s physiological functions. For example, lead inhibits three major enzymes that are involved with the production of heme, the ferrous (iron-based) component of hemoglobin, which is the protein that transports oxygen to the cells and tissues of the body. (Mahaffey) Studies also suggest that insufficient iron intake increases the gastrointestinal absorption and soft tissue concentration of lead. (6)

What about vitamin D, vitamin C and thiamin? Though less is known about how these nutrients protect against lead toxicity, vitamin D appears to modify lead distribution once it has been absorbed, preventing its incorporation into bone. (Cheng). Vitamin C has been shown to have chelating properties which help remove lead from the body. And thiamin (B1) appears to inhibit the uptake of lead into cells and promote lead excretion. (7)

We Are What We Eat — and Animals Are No Exception

It’s also plausible that the diet and living conditions of the animals we use to make bone broth will significantly influence the levels of lead their bones, and thus the broth, contain. Food, water, soil and dust are the largest sources of exposure to lead in farm animals. It appears that cereal grains contribute most to dietary exposure to lead. (8) Although I have not seen any comparative data on this, it’s thus reasonable to assume that pasture-raised chickens who eat a combination of forage and grain-based feed would have lower lead levels than conventionally-raised chickens that eat only grain-based feed.

I hope to have some data that will help answer this question in the coming weeks. Jessica Prentice, one of the worker-owners of the Three Stone Hearth community-supported kitchen in Berkeley, CA, has sent samples of their bone broth in to get tested for lead. They make their broth with pasture-raised chickens, so we’ll have at least one example of lead levels in pastured chicken broth to draw from.

That said, given that the levels of lead in the chicken broth tested in the Medical Hypotheses study were below the EPA established safe upper limit for drinking water, and given the protective effect of several nutrients abundant in Paleo/GAPS diets (and even in broth itself), it seems to me that it’s quite safe to consume 2-3 cups of bone broth per day. This is likely to be even more true if your broth is made from pasture-raised chickens. I recommend Kettle & Fire bone broth as a source of lead-free bone broth.

I’ll continue to investigate this issue and report back if I learn anything that changes my opinion.

268 Comments

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  1. I use a pressure cooker to make stock from free-range chicken bones and cartilege (as well as eating the trimmings of meat from the carcas after the stock has cooled). I wonder if the extra heat generated by the presssure cooker is detrimental?

  2. Interesting article!

    What about if they used distilled water or filtered water instead of tap water? Does that change the results? I have always been instructed not to use tap water when I make chicken broth so would like to see it tested with filtered water.

    • Probably not much. They used a tap water control in this experiment, and the levels of lead in that were 0.89 µg/L. That suggests most of the lead was coming from the cartilage, skin and bones of the chicken.

  3. Also, it said the study was done with ‘organic chickens’ not pastured chickens. I’m thinking that lead amounts might fluctuate significantly depending upon where and how the chickens are raised.

    • Yes, I mentioned that in the article. Jessica Prentice from Three Stone Hearth is having their pasture-raised chicken broth tested, so we’ll soon find out what lead levels are like in at least one sample.

  4. The reason that bone broth gives some people a headache is because of the high gelatin content (which, of course is one of the reasons we consume it – it is healing and nutritious). Gelatin is very high in histamines which as we know can cause various reactions esp. migraine headaches. I stopped consuming bone broth for several months, worked on healing my gut in other ways, and now find that I can tolerate smaller amounts of bone broth. Sometimes I take a histame capsule which seems to neutralize the effects of too much histamine.

      • Yes, I’ve heard it’s more common to react to the glutamate in broth if one has a leaky gut. For most people, this is not a problem. I’m sensitive to MSG and get splitting headaches when I (used to) eat it, but eat bone broth regularly and have never had an issue.

        • I am using homemade bone broth to heal my leaky gut, but get a small headache each time I drink it. As far as I know, I used “clean” beef bones, so it shouldn’t contain MSG (right?) and the gelatin isn’t very high (doesn’t get very jello-y when it’s chilled). Any ideas what else could be causing the problem?

      • @LAURIE ~ Thank you!

        @CHRIS ~ Thank you! So, is it still beneficial to make soup with (grass fed beef or pasture chicken) WITHOUT bones? I have leaky gut and I’m very sensitive to MSG and I have high lead in my heavy metal test. I took a break from all meat/bones for a few months. I used to make a lot of crockpot one soups and cook for hours. I want to start introducing with shorter cook time and no bones to see how that is for some amino acids. I wonder is GELATIN from beef AND poultry both high in histamine?

        • Hi Crosswind – I just found out I have leaky gut. It has been a horrible past 7 weeks! My brain has felt cloudy and like I have been on some drug trip intermittently. Doctors had no idea what was wrong with me. I thought maybe I have IBS, cancer, ulcer, parasite etc… All blood and stool tests came back great, so they have no diagnosis. While at the butcher shop, couple of days ago, I was telling the butcher my symptoms and he said “same thing happened to me years ago. Doctors have no clue about leaky gut cause there is no pill to prescribe. you have leaky gut”.

          I’m interested in what foods you are able to consume and symptoms you had in the beginning. The bone broth seems to be helping. Thanks so much!

    • Hi Laurie,

      Are you kidding me? I incorporated the “healing and nutritious” homemade broths and a TBLS of gelatin in OJ, in hopes of healing my gut, but they could be contributing to my other issues with histamine, like hives, etc. I feel like throwing up my arms, because this is just getting so frustrating. It seems like everything we eat has it’s side effects! I’m wondering how you discovered this. I read Chris’ article on migraines and hives, etc. is it due to the long slow cooking process and leftovers? How are you healing your gut in other ways? Curious. Thanks!

    • Hi

      Several months ago I incorporated weekly crockpot bone broths into my families diet. I can’t confirm whether it was the primary reason, since I’ve been incorporating lots of other healthy dietary and exercise practices into our lives, but my osteo-arthritic knees felt better. And I’m playing ice hockey on the weekends with the kids (which is unbelievable to me)
      Anyway in order to step up the gelatin intake (N=1) I purchased the regular (ie NON-hydrolysate) Great Lakes gelatin.
      After some reading I found that the Hydrolysate variant is probably the appropriate one for my condition, although the kids love using the NON-hydrolysate product for home made “Jellos” 🙂
      In an attempt to test the effects (and hopefully some skin toning) I started adding two tablespoons of the NON-hydrolysate gelatin to my regular diet.
      Both, my wife and I got nauseous twice.
      Last night, after a particularly exercise filled weekend I had a few cups of home made 48 hr bone broth, some of my kids jello and a tablespoon of NON-hydrolysate gelatin before going to sleep.
      Soon afterward (ie 30 minutes) I encountered what appeared to be a recurrence of my long lost migraines (ie., blindness in my eye, followed by crushing headache at night and vomiting this morning). Throughout the day I was shivering and had a few episodes of serious diarrhea. This is similar, though much more severe, than a similar episode last week (ie no blindness or vomiting but general weakness and shivering).

      Therefore my question is whether this sounds like an allergic reaction to gelatin. I considered that perhaps I haven’t had migraines because I have been eating less foods that have glutemates (MSG). Anyway it’s just a guess and at this point I’m ready to throw out the gelatin so any ideas would be greatly appreciated…..

      • There’s a small chance it could be magnesium deficiency exacerbated by the calcium in the broth. I used to get aural migraines especially after eating cheese, broccoli, or yogurt and realized it was severe magnesium deficiency. After taking magnesium, I never had another. It’s been years.

  5. I have the same question about beef broth. I always make mine with a beef bone broth starter that I get from a local farmer who raises pasture fed cows.

    • Rachel, I’ve never heard of bone broth starter. What is it, why and how do you you use it? Thanks so much!

  6. So I won’t stop drinking bone broth after the research findings, but what about giving it to children? Does the analysis change when you have:

    a) a small child with less body weight than an adult

    and/or

    b) an infant, primarily breastfed but also taking in a few (mostly play-with-your-food) solids; say, the 6 mos – 12 mos range?

    Thanks.

    • I’m not going to stop giving Sylvie (18 months) broth. Everyone has to make their own decision, but based on the data I’ve seen, it’s not a concern at her level of intake (which is probably 1/4 cup a day, if that).

      Nor do I think it would be a concern in an infant that is primarily breastfed.

      • Are there any studies on the beneficial effects of comsuming bone broth? Are there any scientific articles on the mineral content of them (apart from this 1934 study – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1975347/pdf/archdisch01497-0052.pdf)? I often hear about the alleged benefits but I wasn’t able to find even one article on the subject. I’ve also read on numerous blogs that for making beef broth I need to simmer the bones for at least 24h to extract the most minerals, but it doesn’t seem to be based on any actual studies. What do you know about the subject?

        Looking forward to reading your book!

  7. I mostly make my broth from New Zealand lamb bones and cartilage (pastured I believe), I wonder how much lead that has.

    I don’t eat chicken since I can’t find a source of non-conventionally raised chicken, so I don’t make or consume chicken bone broth.

    • It was my belief that sheep in New Zealand are not pasture fed anymore, not in the final fattening up at least. I would make sure if what you believe is true. Australian sheep are not pasture fattened anymore.

      • Hi Cassie, well I would think it depends on the source/supplier of the meat in question (can’t generalize on an entire county’s production). The lamb I buy is from a company called “Silver Fern Farms”, it’s a public company so I assume it has a certain level of transparency in its operations. According to their website the animals are pasture fed: http://www.silverfernfarms.co.nz/Our-Products/Commercial-Products/Product-portfolio/Default.asp

        But I guess I should look a bit more into it, so I’ll be asking them by email and on their Facebook page: https://www.facebook.com/pages/Silver-Fern-Farms/302386843124396

        • I live in NZ, and recently contacted Beef + Lamb New Zealand Inc via email to query whether any beef and lamb in NZ was grain finished, and they said all NZ beef and lamb is completely pastured (here in NZ grain is really expensive, unlike in the US for example, but rolling pastures are abundant) 🙂 I know that for the Asian markets at one point some producers toyed with the idea of finishing some beef with grains for a small period of time (as apparently consumers in those markets like the marbling through the beef that obese grain fed cattle get *shudder*) but apparently that proved to be too expensive to be worthwhile. I ♥ our beef and lamb 🙂

        • There seems to be an expression of interest in the possibility of having CAFO on hill country in New Zealand for beef. I keep an eye on the farming pages in our press. Certainly if this is able to be confirmed, I’ll be spreading the facts on various sites. Currently, some diary cows are supplemented with palm kernal extract depending on the state of the diarying finances. On some diary farms here in NZ, the cow’s eat tag denotes how much wheat is dispensed to the cow twice a day when it comes in for milking, depending on its output. I believe 1kg wheat/twice a day is the maximum they get. Watch this space though. There are apparently some CAFO diary operations in this country and there is a push for more of them.

          Feeding lambs and hoggets? Nah, haven’t heard that one. Some wool producing merino wethers are shed-farmed for the quality of the wool e.g. free of briars and matagouri which stain the wool. BTW, Australian merino can come from areas where they mulse their sheep, but NZ merino producers have no need to do this as the flystrike problem isn’t so bad.

      • I’ve never heard of lambs being grain-fed in New Zealand and in my country Australia,the vast majority of lambs are grass-fed;only in drought and in transit to slaughter are lambs fed grain.

      • I can assure you that all sheep in New Zealand are grass fed right throughout their lives. We have some thing like 30 million sheep here so if they are not grass fed and left to range on pastures how on earth would we feed them? Other crops are grown including rape and kale and in some instances, not all, lambs are finished by grazing these crops.

  8. Hello: Seems like the units need to be defined better. µ/L? I think you mean µg/L…
    Also, the 15 µg/L that you reference is the standard for tapwater (an important distinction). For those that want to research it themselves (As well as what went into developing the 15 µg/L, it can be found/downloaded from http://www.epa.gov/region9/superfund/prg/
    Also depending on how bone broth is prepared, as you stated, it is mighty close to 15 µg/L – particularly if you have more than one helping or are consuming other beverages/liquids may add to your lead intake. As another point, lead is a neurotoxin that bioaccumlates in the softtissues and bones – which is why you see higher concentrations in the bone and cartlidge/skin/bone broth. It seems that folks should probaly consume bone broth made with cartiladge/skin or just bones, eat it in moderation – there is a compounding effect for lead as well in our soft tissues and bones over our life span. To read more about lead and how it affects human health http://www.epa.gov/ttn/atw/hlthef/lead.html

    • Typo on the units fixed. According to the data I’ve seen, lead is unlikely to accumulate at 15 µg/L. It will be interesting to see similar measurements for pasture-raised chicken broth as well as beef broth.

    • I have similar concerns. I don’t hold the EPA as an utmost trusted source for my health- rather more of the bare minimum of standards.
      I’ve only begun my understanding of heavy metal toxicity and adrenal fatigue/endocrine malfunctioning. So, I will be looking more into that matter. Thank you for sharing this study to contemplate.

      • I was wondering the same thing. Larger animals would have a longer lifetime exposure, but then again chickens might have a higher body burden due to smaller size.

    • If they were broiler hens (past laying ability), they may be older than the beef cattle. Our chickens and turkeys in New Zealand are generally slaughtered at 42 days old but the organic ones would probably be a bit older as they may be a different breed.

  9. Thank you very much for your analysis. This is a bit more reassuring. Now what about beef bone broth? Being that cows are larger animals than chickens and live longer (though, I don’t know about the age of slaughter), I’m concerned that they would accumulate more lead in their bones that chickens used in the study.This has been an issue with calcium supplements made from cow bones. Also, you talk about adults. What about with young children?

    I’m very upset about this news, but can’t say I’m surprised. I can’t praise bone broth enough for it’s therapeutic value. I’ve been suffering for 8 years after knee surgery with almost constant pain and swelling. Started drinking bone broth twice daily and the pain and swelling went about after about 3 weeks. It’s been several months now and my knee has been great! I’m still amazed.

    • That’s awesome Stuart! We just love hearing all the ways bone broth has changed peoples lives. Good luck on your journey towards optimal health!

  10. Thanks Chris for your fast and thorough investigation of this! I have to be honest, I was pretty worried when I saw this being shared on Facebook yesterday. I will be interested to know the results of those who choose to have their bone broth tested – any resources of where we might be able to do so if we would like to do the same?

  11. Good reason to use clean, filtered water, grass-fed animals, keep our detox organs healthy and keep on detoxing. I just don’t see how this day and age we can afford to stop.

    • Yeah I was wondering why they didn’t use filtered water instead of tap? Perhaps the tap water is what is contributing to the higher amounts of lead.

  12. Thank you Chris, I really appreciate all your research, and while it is a bit disturbing, I appreciate your factual and level headed perspective on the subject. I really respect your opinion on these things, thank you again.

    • Hoffe, Your comment is interesting as I jumped on the bone broth band wagon with grass fed beef bones, but every time I drank it, I immediately got a pounding headache. So I’m wondering if it is the glutamates since I know I have sensitivities to MSG, it makes sense. – thanks!

        • Iris, Thank you!!!.. I’ve been wondering this and trying to find this answers. Even a chef didn’t know. I thought based on comments it was longer time that produced the free glutamates. I will cook less time.

      • It also depends on the temperature your stock is cooked at. If your stock is boiled over a long period the natural MSG will be much higher. Just bring your stock to a boil and then turn down to the lowest setting and let it gently simmer for 8 – 48 hours. The lower temp won’t produce as much MSG apparently.

    • I’ve heard that having sufficient Vitamin K and K2 will mop up excess glutamates. If you are having sensitivities to glutamates, you might want to check into this. Especially K2, as it’s hard to come by in food sources, yet is an important nutrient.

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