Characterization of the Lipid Composition at the Proximal Root Regions of Human Hair

The study examined the lipid composition of hair from 44 Japanese females aged 1 to 81, focusing on eight lipids: hydrocarbons (HCs), squalene (SQ), wax esters (WEs), triglycerides (TGs), fatty acids (FAs), cholesterol (CH), ceramides (CERs), and 18-methyl eicosanoic acid (MEA). Hair samples were taken from the proximal root end and analyzed using chromatography. The lipids were classified into four groups based on their origins and correlations: group A (SQ, WEs, TGs, FAs) from sebum, group B (CH, CERs) as endogenous lipids, group C (HC) of unknown origin, and group D (MEA) as another endogenous lipid. Principal component analysis revealed a negative correlation between lipids in groups A and B, suggesting that group B lipids act as a barrier against sebum-derived lipids. The study concluded that CH, CERs, and MEA should be considered intrinsic internal lipids of human hair.