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.
