Qualitative Analysis of Human Milk Produced by Women Consuming a Maize-Predominant Diet Typical of Rural Mexico

Abstract

The milk composition of women on a typical rural Mexican diet was compared with that secreted by American women, consuming a diet typical of affluent countries. Milk concentrations of free fatty acids, cholesterol, total amino acids, and selected key minerals were analyzed at 4 or 6 months postpartum. The total milk fat concentration was lower in the 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 not differ, cholesterol, expressed in terms of total lipid, was higher in the Otomi milk (3.9 ± 1.1 vs. 3.1 ± 0.7 mg/g fat, p = 0.005). Saturated medium-chain (C10:0–C14:0) and unsaturated intermediate-chain fatty acids (C16:1 and C18:2) were higher in the Otomi than in the American 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 concentrations of protein and nonprotein nitrogen were comparable between the two groups. The concentrations of serine, proline, cystine, methionine, and tryptophan were higher in the Otomi than in the American milk (p < 0.05–0.001). The concentrations of valine and isoleucine were significantly lower in the Otomi milk (p = 0.05). Expressed per gram of milk protein, the cystine, methionine, lysine, and tryptophan concentrations 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 fatty acid and amino acid patterns and mineral content are unlikely to affect infant growth, but may have other biological consequences yet to be ascertained.

Human milk fatty acid composition from nine countries varies most in DHA

“…The lauric and myristic acid levels of milk in the group consuming the fat-free diet were much higher than levels in women consuming the fatcontaining diet. Studies of milk composition from women whose typical diet was low in fat agree with our finding that lauric and myristic acid levels are elevated (19,28,29).…”

“…Parallels can be seen between the levels of several milk FA and maternal diets. For example, our data demonstrated that milk LA levels were relatively high in countries typically consuming a high-maize diet, such as Mexico (19) and Chile (20). The Philippines presented an unusual profile, with low LA levels and high levels of lauric and myristic acids, most likely indicating consumption of diets limited in both essential FA and total fat.…”

Docosahexaenoic Acid Supplementation from Mid-Pregnancy to Parturition Influenced Breast Milk Fatty Acid Concentrations at 1 Month Postpartum in Mexican Women

“…Mean breast milk DHA concentrations in our study population are similar to those seen in women in the US and other countries where dietary DHA consumption is lower than recommended (16,18). A study of Otomi women living in rural Mexico found a lower concentration of ALA, a similar concentration of AA, and a higher concentration of LA in breast milk (32).…”

Global Standard for the Composition of Infant Formula: Recommendations of an ESPGHAN Coordinated International Expert Group

“…The reference unit in the different sources is not the same although expressed as mg amino acid per g protein. For example ''protein'' is the sum of total anhydrous amino acids (18,24) or total nitrogen multiplied by 6.38 (23) or total nitrogen minus NPN multiplied by an unknown factor (25). To avoid this problem it seems advisable to refer the individual amino acid content to the nitrogen content to avoid confusion about the nature of the protein calculation, as suggested by the Infant formula should contain per 100 kcal an available quantity of each of the amino acids listed at least equal to that contained in the reference protein, as shown in this table.…”