From the article:
"B12 is the only vitamin synthesized solely by certain microorganisms—many of which are abundant in soil. And the only vitamin containing a trace element: cobalt. B12 owes its chemical name—cobalamin—to the cobalt at the center of its molecular structure. Humans and all vertebrates require cobalt, though it's assimilated only in the form of B12.
Cobalt is important in the plant world. Bacteria on root nodules of legumes (beans, alfalfa, clover) require cobalt (and other trace elements) to synthesize B12 and fix nitrogen from air. Soybeans grown without cobalt are severely retarded in growth and exhibit severe nitrogen deficiency, leading to death in about one of four plants. Adding only a few ounces of cobalt per acre can resolve deficiency symptoms in ten to 21 days.
Cobalt deficiency is far more dramatic in animals, particularly ruminants (cattle, deer, camels, and sheep) grazing on deficient pasture. These animals obtain all their B12 from their gut bacteria, but only if bacteria are provided cobalt salts from pasture. Legumes with less than 80 parts per billion (ppb) cobalt can't meet ruminant B12 needs. Under deficient conditions, calves and lambs thrive and grow normally for a few months as they draw on B12 reserves in liver and other tissue, but soon exhibit gradual loss of appetite and failure to grow, followed by anemia, rapid weight loss and finally death. Marginally deficient pastures cause birth of weak lambs and calves that don't survive long. These symptoms mirror B12 deficiency in human infants.
To prevent or alleviate cobalt-B12 deficiency, farmers routinely add cobalt to animal feeds or salt licks. Some fertilize pastures with cobalt-enriched fertilizers; others opt for periodic quick-fix B12 injections. With any of these measures, all symptoms are reversed and B12 in milk and colostrum dramatically increases.
The implication for humans subsisting on vegetarian diets are profound. B12 synthesis by indigenous bacteria is known to occur naturally in the human small intestine, primary site of B12 absorption. As long as gut bacteria have cobalt and certain other nutrients, they produce B12. In principle then, internal B12 synthesis could fulfill our needs without any B12 provided by diet.
But if cobalt in our diet is on the wane, perhaps the problem isn't so much lack of B12-synthesizing intestinal flora as lack of cobalt, the element with which bacteria weave their magic. The burning question then is: how cobalt deficient is our soil? "