Vitamin B12 synthesis by human small intestinal bacteria.
Level 5 - mechanism / opinion, no new human data
Laboratory and microbiological bench study with no clinical trial data
PubMed 7354869 · doi:10.1038/283781a0
What was done
The study examined bacteria residing in the human small intestine—noted to be extensive in healthy southern Indian subjects—to evaluate whether specific bacterial isolates synthesize vitamin B12 (cyanocobalamin). Isolation and culture methods are not detailed in the abstract.
What was found
At least two groups of small bowel organisms, Pseudomonas and Klebsiella species, were shown to synthesize significant amounts of vitamin B12. The abstract reports no numerical values, concentrations, or statistical data.
Why it matters
Because physiological B12 absorption occurs in the ileum and colonic bacterial B12 is unavailable to humans, synthesis by upper small intestinal bacteria could represent an endogenous source of bioavailable vitamin B12.
Limits
The abstract lacks sample size, subject details, quantitative values, and assay methods. It was not measured whether this synthesized B12 is physiologically absorbed or clinically prevents deficiency in humans.
Cited by
- contradicts All eight B vitamins are synthesized by human intestinal bacteria and can be absorbed by the host.