Slide 1: Which of the following essential nutrients is found in animal products but cannot be synthesized by any animal? A) B3- niacin. B) B7- biotin. C) B9- folate. D) B12- cobalamin.

Slide 2: D) B12- cobalamin. Vitamin B12 can only be synthesized by bacteria and archea. Some of these bacterial species live in the soil, and animals that eat grasses from these soils possess them as normal flora. The B12 made by these bacteria is absorbed from the animals’ GI tracts. Later, when we eat meat, dairy or eggs, we get the B12 we need for cellular metabolism.

Slide 3: Bonus! Vitamin B12 is the largest and most complex of the B vitamins. It contains cobalt and cyanide, which (only in their inorganic forms) are both toxic to humans. Bonus bonus: Inorganic cobalt is present in some joint implants, and cobalt-induced T-cell mediated inflammation has been implicated as a potential culprit in the pathophysiology of implant failure.


  • Vitamin B12. Office of Dietary Supplements. National Institutes of Health. NIH
  • Posada OM, Tate RJ, Grant MH. Toxicity of cobalt-chromium nanoparticles released from a resurfacing hip implant and cobalt ions on primary human lymphocytes in vitro. J Appl Toxicol. 2015 Jun;35(6):614-22. Epub 2015 Jan 21. PMID 25612073

Tags: , ,