Bone Broth Has (Some) Lead
bones are known to sequester the heavy metal lead, contamination with which is widespread throughout the modern environment. Such sequestered lead can then be mobilised from the bones … broth made from skin and cartilage [of already cooked chicken] and chicken-bone broth, were both found to have markedly high lead concentrations, of 9.5 and 7.01 μg L−1via
Caveat: this is only 10x the amount in their tap water. I’m not sure if this is enough to matter, but small amounts of lead hurt IQ detectably (on a population level)