Glutathione peroxidase activity modulates fatty acid profiles of plasma and breast milk in Chinese women

Since little is known about the effect of selenium on the fatty acid profil es (FAP) of human breast milk, the purpose of this study was to measure the effect of habitual dietary selenium (Se) intake on this profile in plasma and breast milk. Subjects were lactating women from three locations in Chin a where habitual selenium intakes are extremely low (Xichang), adequate (Be ijing), or extremely high (Enshi). Plasma and milk samples were obtained wi thin seven days of parturition(early samples) or within eighteen months pos tpartum (mature samples) and analyzed for selenium concentration, glutathio ne peroxidase (Gpx) activity and FAP. Plasma and milk selenium concentratio ns were significantly lower in the samples from women from Xichang and sign ificantly higher in those from Enshi when compared to those from Beijing. P lasma Gpx activity, however, was higher in samples from Beijing than Xichan g or Enshi. In contrast, the early breast milk samples had similar Gpx acti vity regardless of location. The mature samples, however, followed the same trend as plasma with the samples obtained from the women in Beijing having the highest activity. Of the unsaturated fatty acids examined, the concent ration of linoleic acid, 18:2(n-6), in both plasma and milk was greater in the samples from Beijing when compared to those from Xichang or Enshi. Thus dietary selenium appears to influence the fatty acid composition in human breast milk, but influences Gpx activity only in mature milk samples.