The occurrence of unusual fatty acids in faecal lipids from human beings with normal and abnormal fat absorption

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Abstract
Human faecal lipids of subjects both with normal and abnormal fat absorption have a fatty acid composition very different from that of the ingested fats. A variety of isomeric octadecenoic acids are present, with the double bond in positions 4, 5, 6, 7, 8, 9, 10, 11 and 12. Approximately 50% of these oleic acid isomers possess the trans-configuration about the double bond. Subjects with steatorrhoea do not excrete increased amounts of trans-acids on changing the dietary fat from butter (2-3% of linoleic acid) to corn oil (51% of linoleic acid). On a diet of butter, subjects with steatorrhoea appear to excrete linoleic acid in amounts equal to that ingested. No support is found for the theory that trans-octadecenoic acids are produced by bacterial hydrogenation of linoleic acid. A new major component of faecal lipids has been shown to be 10-hydroxystearic acid, together with 6-, 7-, 8- and 9-hydroxystearic acids as minor components. These hydroxy acids are suggested as intermediates in the formation of monounsaturated octadecanoic acids from stearic acid.