QUALITATIVE-ANALYSIS OF HUMAN-MILK PRODUCED BY WOMEN CONSUMING A MAIZE-PREDOMINANT DIET TYPICAL OF RURAL MEXICO

The milk composition of women on a typical rural Mexican diet was comp ared with that secreted by American women, consuming a diet typical of affluent countries. Milk concentrations of free fatty acids, choleste rol, total amino acids, and selected key minerals were analyzed at 4 o r 6 months postpartum. The total milk fat concentration was lower in t he Otomi (22.7 +/- 6.7 mg/g milk) than in the American women (31.3 +/- 5.4 mg/g milk, p = 0.001). Although the absolute concentration did no t differ, cholesterol, expressed in terms of total lipid, was higher i n the Otomi milk (3.9 +/- 1.1 vs. 3.1 +/- 0.7 mg/g fat, p = 0.005). Sa turated medium-chain (C 10:0-C 14:0) and unsaturated intermediate-chai n fatty acids (C16:1 and C18:2) were higher in the Otomi than in the A merican milk (p < 0.03). The concentrations of C16:0, C18:0, and C18:1 were significantly lower in Otomi than in American milk, The milk con centrations of protein and nonprotein nitrogen were comparable between the two groups. The concentrations of serine, proline, cystine, methi onine, and tryptophan were higher in the Otomi than in the American mi lk (p < 0.05-0.001). The concentrations of valine and isoleucine were significantly lower in the Otomi milk (p = 0.05). Expressed per gram o f milk protein, the cystine, methionine, lysine, and tryptophan concen trations were higher, and the glutamine/glutamate, valine, isoleucine, and arginine levels were lower in the Otomi milk. The concentrations of phosphorus and copper were lower in the Otomi than in the American milk at 4 months postpartum (p = 0.05). These differences in milk fatt y acid and amino acid patterns and mineral content are unlikely to aff ect infant growth, but may have other biological consequences yet to b e ascertained.