Essential and toxic metals in animal bone broths

Hsu DJ, Lee CW, Tsai WC, Chien YC · Food & Nutrition Research

Calcium and magnesium came to under 5% of daily recommended levels per serving even after long acidified cooking; lead was 1.5-2.1 µg per serving and cadmium 0.1-0.3 µg, at hazard quotients under 0.01 of their reference doses. But the modifiers are large: dropping pH from 8.38 to 5.32 raised Ca and Mg extraction 17.4-fold and 15.3-fold, and cooking beyond 8 h extracted significantly more than shorter times (Ca 201 to 361 mg/kg, Mg 8.2 to 120 mg/kg from 0.5 h to 12 h). Two minerals do better than the headline: chromium averaged about a tenth of its reference intake and reached a fifth in an extreme case, and one serving of the beef-noodle broth supplied 16% of the iron intake. The paper does not dispute the earlier chicken-bone lead measurement — it calls its own compatible with it — and disputes what follows from it.

Population

Laboratory analysis of experimentally prepared broths and of three commercial Taiwanese bone-broth dishes (no human subjects)

Intervention

Broths varying cooking time, acidity, bone type, and species; Ca, Mg, Fe, Zn, Cu, Cr, Al, Pb, Cd measured

Limitations

Composition study only; no biological outcomes; broth recipes vary enormously so generalization is limited, and the three commercial products are Taiwanese restaurant dishes — a pork-rib herb stew, a Japanese-style pork-bone noodle broth and a Chinese-style beef noodle — rather than the bottled bone broth sold for joints. The authors add one caution the mineral numbers do not: a large volume of long-simmered broth carries fat-soluble compounds out of marrow, vitamin D among them. Funded by Taiwan's Ministry of Science and Technology; no conflicts declared.