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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #62557
Title: WHOLE BODY PROTEIN TURNOVER IN THE FED STATE IS REDUCED IN RESPONSE TO DIETARY PROTEIN RESTRICITON IN LACTATING WOMEN

Author
item MOTIL, KATHLEEN - BAYLOR COLL OF MEDICINE
item DAVIS, TERESA - BAYLOR COLL OF MEDICINE
item MONTANDON, CORINNE - BAYLOR COLL OF MEDICINE
item WONG, WILLIAM - BAYLOR COLL OF MEDICINE
item KLEIN, PETER - BAYLOR COLL OF MEDICINE
item REEDS, PETER - BAYLOR COLL OF MEDICINE

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: It is important for women who are breastfeeding babies to get sufficient protein from their diets, for the sake of the health of the women as well as that of their babies. However, many women of childbearing age eat food that contains marginal amounts of protein as well as protein that is of poor quality. Breastfeeding puts women under metabolic stress. We examined how lactating women responded to a diet limited in protein in order to fin out whether their metabolic responses differed from those of women who were not lactating. We discovered lactating women were better able to retain protein, at all levels of intake, than nonlactating women. Their bodies adapted to protein restriction by breaking down protein more slowly than they synthesized it. We also showed that 13C amino acid tracers serve as a useful marker of protein metabolism in lactating women.

Technical Abstract: Little is known about the metabolic mechanisms that enable the reproductive women to maintain her nutritional status as well as her lactational performance despite the consumption of inadequate dietary protein. We examined the adaptive responses of body protein metabolism to dietary protein restriction in lactating women to determine whether their responses sdiffered from those of nonlactating women. Thirteen healthy women (5 lactating, 4 nonlactating postpartum, 4 nulliparous) aged 28-32 y were given protein intakes of 1.5, 1.0, and 0.4 gúkg-1úd-1 over 3-d periods, respectively. At the end of each period, while in the fed state, subjects received orally, a single bolus dose of (1-13C)leucine. A 24-h urine collection was obtained simultaneously. Whole body protein metabolism was characterized using the end-product model based on nitrogen excretion and leucine catabolism. Nitrogen flux and rates of protein degradation and synthesis in the fed state were significantly lower at all dietary protein levels in lactating women than in their nonlactating counterparts. Net protein retention in the fed state was significantly higher in lactating women than in nonlactating women because of the relatively greater reduction in protein degradation than in protein synthesis. These studies suggest that lactating women rapidly adapt to dietary protein restriction by downregulating protein metabolic activity, and that (13C) amino acid tracers serve as a useful metabolic marker to determine the adequacy of the dietary protein content of lactating women.