Taurine content in breast milk of Mexican women from urban and rural areas.

The concentration of the most abundant free amino acids in breast milk, taurine, glutamic acid, glycine + threonine, alanine and glycine was measured in breast milk samples obtained from Mexican women from an urban population (38 samples) and from a rural population (106 samples). Free amino acid levels including taurine in the urban group were essentially similar to those reported in samples from American and Canadian women (taurine concentration: 332-357 nmol/ml) but significantly lower content of taurine (237-259 nmol/ml) was found in the rural group. The only other significant difference between the two groups was a 32% higher concentration of alanine in the rural group as compared to the urban group. The observed differences may result from a lower dietary intake of taurine containing food in the rural group as this group reported a restricted consumption of meat, the most abundant dietary source of taurine. Because taurine synthesis is low in primates including human, a decreased external supply of taurine may explain the observed reduction in the taurine content of milk. The increase in alanine may represent a compensatory mechanism for the decrease in taurine.