Soledad DeSantiago

Amino Acid Intake During Lactation and Amino Acids of Plasma and Human Milk

The aim of this study was to determine the free amino acid pool in plasma and milk in marginally nourished lactating women. Twenty-eight rural women (age, 23.9+/-5y; weight 50.2+/-4.9 kg; height, 148.2+/-4.8 cm) were studied under metabolic balance conditions. Subjects were divided into 6 groups (5-6 women in each), representing rural mothers postweaning and in the 15, 3rd, and 6th months of lactation; nonpregnant, nonlactating controls were from rural and urban areas. Amino acid analyses of diet and of plasma and milk samples were performed using a Beckman 6300 amino acid analyzer. Lysine intakes were lower than the recommended intake for lactating women (RDA). Plasma amino acid profiles differed between the lactating and weaned groups: aspartate and isoleucine increased at the 6th month (P < 0.05), while valine declined over weaning time (P < 0.05). In milk, valine and proline decreased at the 6th month (P < 0.05), while serine rose at the 3rd month. Free amino acid pools were 1- to 15-fold higher in plasma than in milk for branched-chain amino acids and basic, aromatic, and neutral amino acids. In mammary tissue these amino acids can be channeled to tissue and milk protein synthesis or to catabolic pathways. Glutamate was 40-fold higher in milk with respect to plasma content. This was the predominant amino acid in the free amino acid pool in milk. These results suggest selective amino acid transport in mammary tissue during lactation.

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

Abstract 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 BWd. Total amino acid concentration in plasma was: 2212.6 ± 176.4 μmol/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 μmol/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

Negative Balance of Calcium During Lactation in Marginally Nourished Women

Thirty-three rural Mexican women (age, 18-36y; weight, 50.3+/-3 kg; height, 148.3+/-2 cm) were studied under metabolic balance conditions. The objectives were to study the metabolic balances of calcium and phosphorus at the 1st, 3rd, and 6th months of lactation and postweaning and to determine the incorporation of calcium and phosphorus in milk. Subjects were divided into 5 groups of 5 to 10 each, representing: the 1st, 3rd, and 6th month of lactation, postweaning, and a control group of nonpregnant, nonlactating women. Metabolic balance was determined using identical diets and analysis of 24-hour urine (3 d), 72-hour feces, and 24-hour milk samples. Calcium content was determined by atomic absorption spectrophotometry and phosphorus by a colorimetric method. Calcium content in milk was similar at the 1st, 3rd, and 6th months. Positive calcium balances were observed in the control group, while balances were very negative in all lactation groups (-721.6+/-248 mg/d). Calcium urinary excretion was higher in the control and postweaning groups (P < 0.05), suggesting a regulatory mechanism to conserve calcium during lactation. No differences were observed in phosphorus content in milk at the 1st, 3rd, and 6th months. Positive balances were observed in the control and postweaning groups (331+/-139 and 87.1+/-130 mg/d, respectively, mean +/- SD), while the lactation groups presented more subjects (approximately 75%) in negative balance (mean +/- SD of -180.6+/-392 to -439+/-146 mg/d). High fecal calcium and phosphorus excretion (approximately 1,500 mg/d) likely contributed to the negative balance during lactation.

Metabolizable energy from a predominantly vegetable diet consumed by Mexican rural lactating women

Abstract Metabolizable energy from the habitual diet was measured in lactating women from a Mexican rural community. Food intake was estimated in 12 women, age 25 ± 5 y, 2–6 m postpartum, body weight 48 ± 4 kg and height 147 ± 4 cm. Rural diet was predominantly from vegetable sources based on maize (tortillas), beans, tomato, onion and chili. The group was studied in free conditions with their habitual diet intake and in balance conditions consuming a controlled diet similar to their rural diet. Four women participated in a second balance with a modified diet, low in fiber and higher in protein and fat content in comparison with the habitual rural diet. Metabolizable energy was lower (P 22%) than with the rural diet. Metabolizable energy from the rural diet by the lactating women group was lower (8.1 MJ/d) than the energy recommended allowances during lactation. Nutrient digestibility from the rural diet was similar to those found in populations with intake of predominantly vegetable diets with high dietary fiber content.