Breast milk and erythrocyte fatty acid composition of lactating women residing in a peri‑urban South African township.

Data on breast milk fatty acid (FA) composition in South African lactating women in relation to their FA status, as well as on potential compositional changes within feed, are limited. The aim of this study was to assess the FA composition of breast milk sampled at three time points within feed, and to determine associations with red blood cell (RBC) total phospholipid FA levels in lactating South African mothers of 2-4-month-old breastfed infants. FA composition (% total FAs) was analyzed in RBC total phospholipids, and in fore-, mid-feed and hind-milk samples of lactating mothers (n = 100) of Black African descent living in a peri‑urban township. The mean age of the lactating women was 27.8 ± 6.8 years. Geometric mean (95% CI) breast milk SFA, MUFA and PUFA contents were 37.7 (37.3,38.1), 28.5 (27.9, 28.8), and 23.5 (23.2, 24.5)%, respectively. Breast milk DHA and AA contents were 0.25 (0.24, 3.71) and 0.81 (0.79, 0.83)%, respectively, in fore-, mid- and hind-milk combined. Maternal RBC EPA, DHA and AA levels were 0.37 (0.34, 0.40), 3.8 (3.6, 4.0) and 15.4 (14.8, 16.1)%, respectively. Women who reported to consume fish often (n = 3) had significantly higher RBC EPA levels than women who consumed fish sometimes (n = 56), never (n = 14) or rarely (n = 19). Breast milk DHA positively correlated with maternal RBC DHA, while no correlations were found between breast milk AA and maternal RBC AA. Breast milk ALA and DHA contents were significantly higher in mid-feed [ALA= 0.8 (0.2, 0.2), DHA=0.3 (0.2, 0.3)] and hind-milk [ALA=0.8 (0.8, 0.9), DHA=0.3 (0.3, 0.3)] than foremilk [ALA=0.8 (0.7, 0.9), DHA=0.2 (0.2, 0.3)]. In contrast, LA and AA contents remained constant within feed. In this sample of peri‑urban South African lactating mothers, breast milk was low in DHA and high in AA compared to global means. Breast milk DHA was associated with maternal RBC status, while breast milk AA was not. We further showed that breast milk ALA and DHA increased, while LA and AA remained unchanged within feed. This suggests that n-3 PUFA maybe preferentially transferred to breast milk within feed through biomagnification.