 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, maybe the main concern, but there's a number of other toxic responses connected with the consumption of meat products. Lead, for example, can be toxic to the nerves, like 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, were 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 that's fed to farmed animals like farmed fish. If some tilapia is fed tuna by-products, they could bioaccumulate heavy metals and pass them on to us. The highest levels have been found in frozen soul filets, 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 in hyperuricemia, elevated levels of uric acid in the blood. According to the Centers for Disease Control and World Health Organization, a blood lead level less than 25 micrograms per deciliter to be not 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 quote-unquote acceptable range, lower lead meant 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's no such thing as a safe level of exposure to lead. And once it gets into 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 not get exposed in the first place. If it builds up in bones, though, what about boiling bones for broth? We know bone 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 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? They did only use bones from organic, free-range chickens.