Influence of short-chain fatty acids on iron absorption by proximal colon.

BACKGROUND

Short-chain fatty acids produced by bacterial fermentation in the colon enhance the local absorption of cations, such as calcium, that could be used to improve the bioavailability of iron if a significant colonic absorption of iron were to occur.

METHODS

Iron (iron gluconate, 100 microM) absorption by the caecum of the rat was compared with that in proximal sites of the small bowel using the Ussing chamber model; the influence of probiotic bacteria (Propionibacterium freudenreichii) on iron absorption was assessed and compared with that of two of their fermentation products (acetic and propionic acids) using the Ussing chamber and the ligated colon with gamma emitting iron as experimental models.

RESULTS

The caecum absorbed less iron than the duodenum, but significantly more than the jejunum and ileum. This occurred mainly through an enhanced mucosal transfer of iron uptake. Propionibacteria enhanced iron absorption from the proximal colon; the same effect was observed in the presence of viable bacteria, or the culture medium free of viable bacteria, or acetate and propionate or propionate alone.

CONCLUSIONS

The proximal colon could be a significant site available for iron absorption; this absorption can be enhanced by local production of short-chain fatty acids such as propionate.