[13C]linoleic acid oxidation and transfer into milk in stunted lactating women with contrasting body mass indexes.
BACKGROUND
The fat concentration of human milk is associated with maternal adiposity, but there is no clear understanding of the mechanisms controlling milk fat concentration.


OBJECTIVE
We evaluated the effect of postpartum body mass index (BMI; in kg/m(2)) on the metabolic distribution of an oral dose of [13C]linoleic acid in lactating women.


METHODS
Ten lactating women stratified by BMI (either <22.5 or >23.5) at 5 mo postpartum received orally 2.5 mg [13C]linoleic acid/kg body wt. Exhaled air, milk, and plasma samples were collected in relation to tracer administration. Linoleic acid was determined by gas chromatography. Dietary intake, serum, milk composition, [13C]linoleic acid enrichment in milk and plasma, and exhaled 13CO2 (by isotope ratio mass spectrometry) were assessed.


RESULTS
Women with a higher BMI exhaled more 13CO2 than did women with a lower BMI (22.8 +/- 9.4% compared with 8.6 +/- 3.5% of dose, P < 0.03). Cumulated 72-h transfer of [13C]linoleic acid to milk was not significantly different between groups (14.8 +/- 6.5% compared with 17.7 +/- 6.7% of dose). Within the first 9 h after dose administration, 51.6 +/- 4.9% of the total isotope transfer into milk had passed in women with a higher BMI, but only 24.0 +/- 15.3% had passed in those with a lower BMI (P = 0.02).


CONCLUSIONS
Women with a lower BMI, who were reputed as having less body fat, oxidized and secreted into milk less dietary linoleic acid within 12 h after tracer administration than did women with a higher BMI. In both groups, a large proportion of [13C]linoleic was retained in the maternal compartment, most likely fat tissue, in a slow turnover pool, and released slowly in later hours.
Villalpando
S
S
Unidad de Investigación en Nutritción, Hospital de Pediatría, CMN, Instituto Mexicano del Seguro Social, Mexico City, Mexico. svnutri@data.net.mx
Del Prado
M
M
Lance
A
A
Alfonso
E
E
Rodríguez
M
M
Demmelmair
H
H
Koletzko
B
B
D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001827:Body Height; D015992:Body Mass Index; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D002849:Chromatography, Gas; D005260:Female; D006801:Humans; D007774:Lactation / Q000378:metabolism*; D019787:Linoleic Acid / Q000008:administration & dosage* / Q000378:metabolism* / Q000493:pharmacokinetics; D008895:Milk, Human / Q000737:chemistry*; D010084:Oxidation-Reduction
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D019787:Linoleic Acid