Essential and toxic metals in animal bone broths

Background: This investigation examines the extraction of metals from animal bones into broth, and assesses whether bone broths are good sources of essential metals and the risks associated with the consumption of toxic metals. Method: Three sets of controlled experiments were performed to study the factors (cooking time, acidity, bone type and animal species) that influence metal extractions. Three types of animal bone broth-based foods were also tested. Results: Reducing the broth pH from 8.38 to 5.32 significantly (p < 0.05) increased Ca and Mg extraction by factors of 17.4 and 15.3, respectively. A long cooking time, > 8 h, yielded significantly higher (p < 0.05) Ca and Mg extraction than shorter cooking times. The extraction characteristics of metals, particularly Ca, Mg, Cu and Al, from the leg and rib bones differed. The between-species variations in extraction were larger than those of within-species. Conclusions: The Ca and Mg levels in home-made or commercial broth/soup were found not to exceed low tenths of milligram per serving, or < 5% of the daily recommended levels. The risks that are associated with the ingestion of heavy metals such as Pb and Cd in broth are minimal because the levels were in the ranges of a few mu g per serving.