Amino acid profiles in diet, plasma and human milk in Mexican rural lactating women

This study was designed to assess the relation between the amino acid pattern consumed by marginally nourished lactating women, and the amino acid profiles in plasma and milk. Ten lactating women from a Mexican rural community, with an age of 19-29 (y), a postpartum time 15 (w), and a weight of 49 (kg), were studied in a metabolic unit. Experimental diet was similar to the rural habitual diet and it was given for 10 days. On the last 4 days urine, feces, milk and blood samples were collected. Measurement of total nitrogen in urine, feces and diet, and amino acid analysis in diet, plasma and milk were performed. Amino acid score of the habitual diet was : Lys as a limiting amino acid (18.5%), and Phe+Tyr (137.9%) in excess. Lys intake (21.8 +/- 4.6 mg/g protein) was lower than the consumption recommended for lactating women (31 mg/g protein). Nitrogen balance was -9.6 +/- 15.4 mg/kg BW/d. Total amino acid concentration in plasma was: 2212.6 +/- 176.4 mu mol/L, where indispensable and dispensable amino acids were 33% and 67% respectively; the most abundant amino acids were Ala, Glu, Gly, Lys and Val; and the less abundant were Cys and Asp. Total amino acid concentration in milk was: 24090 +/- 1228 mu mol/L, containing 42% and 58% of indispensable and dispensable amino acids respectively; the most abundant amino acids were Glu, Pro and Leu, and the less abundant were Cys, Trp, and Met. The results showed a correlation between the concentration of some indispensable amino acids present in the diet with those of milk (p<0.05). This study shows novel results about amino acid relation between habitual diet, plasma and milk in rural lactating women studied in balance conditions. (C) 1999 Elsevier Science Inc.