Growth of <i>Bifidobacterium</i> species is inhibited by free fatty acids and bile salts but not by glycerides

High-fat diets have been associated with lower gut and fecal abundances of genus Bifidobacterium . Here, we investigated whether commonly consumed dietary free fatty acids have any detrimental effect on the growth of B. adolescentis , B. bifidum , and B. longum . We found that the presence of free fatty acids in the medium inhibits the growth of Bifidobacterium species to a varying degree, with capric (C10:0), oleic (C18:1), and linoleic (C18:2) acids displaying the largest effect. In comparison, free fatty acids did not affect the growth of Escherichia coli . When fats were added as a mixture of mono- and diacylglycerols, the inhibitory effect on Bifidobacterium growth was abolished.