Variation in sebum fatty acid composition among adult humans.

Quartz capillary gas chromatography was used to analyze the wax ester fatty acids of 4 sebum samples collected at 2-week intervals from each of 10 adult human subjects. Marked differences in wax ester fatty acid composition between subjects were apparent. The greatest variation was present in the even-carbon-numbered iso-branched acids, which ranged from 1-22% of the monounsaturated acids and from 1-13% of the saturated acids. The anteiso chain structures formed 3-7.5% of the unsaturated acids and 3-13.5% of the saturated acids. Fatty acids bearing one or more methyl branches at other positions in the chain made up 12-22% of the saturated acids, but were not present in the unsaturated fatty acid fraction. This and other features of the composition of the unsaturated fatty acids indicate that the delta 6-desaturase that produces the monounsaturated fatty acids of human sebum requires a substrate having a straight chain of at least 12 carbon atoms extending from the carboxyl group. The differences in fatty acid composition between subjects and the constancy of composition for each of the subjects over the 2-month period indicate that the synthesis of each of the types of chain structure is under genetic control.