T J Quinn1, G B Carey. 1. Department of Kinesiology, University of New Hampshire, Durham 03824, USA. tjq@christa.unh.edu
Abstract
PURPOSE: This study examined the relationships among diet, exercise intensity, and breast milk composition in lactating women. METHODS:Twelve lactating women were randomly assigned to either a high (N = 6; 5.03 g carbohydrate (CHO) x kg body mass (BM)(-1)) or moderate (N = 6; 3.89 g CHO x kg BM(-1)) carbohydrate diet. Milk and blood samples were collected before and after a nonexercise session (control) and maximal, lactic acid-threshold (LAT), and 20% below the LAT (LAT-20) intensities. RESULTS: The 30-min exercise LAT bout was more stressful than the 30-min LAT-20 bout (rating of perceived exertion (RPE) = 15 vs 12, respectively, P < 0.05). Milk LA was significantly higher at 0 min following maximal exercise in the high and moderate CHO groups (1.27+/-0.56 and 1.52+/-0.49 mM, respectively) and following LAT exercise (0.19+/-0.16 and 0.25+/-0.12 mM, respectively), when compared with the control session (0.08+/-0.03 and 0.09+/-0.05 mM, respectively). This was not observed following the LAT-20 exercise in the high and moderate CHO groups (0.11+/-0.04 and 0.12+/-0.08 mM, respectively). Elevated milk LA persisted in the 30-min collection point after maximal exercise only. There was no significant effect of dietary treatment on milk or blood LA at any of the collection points. CONCLUSIONS: In lactating women whose caloric needs are being met: 1) dietary CHO intake, within a practical range, does not influence LA levels in breast milk at rest or after exercise; 2) LA appearance in the milk is a function of exercise intensity; and 3) moderate intensity exercise (RPE = 12) will not increase breast milk LA levels.
RCT Entities:
PURPOSE: This study examined the relationships among diet, exercise intensity, and breast milk composition in lactating women. METHODS: Twelve lactating women were randomly assigned to either a high (N = 6; 5.03 g carbohydrate (CHO) x kg body mass (BM)(-1)) or moderate (N = 6; 3.89 g CHO x kg BM(-1)) carbohydrate diet. Milk and blood samples were collected before and after a nonexercise session (control) and maximal, lactic acid-threshold (LAT), and 20% below the LAT (LAT-20) intensities. RESULTS: The 30-min exercise LAT bout was more stressful than the 30-min LAT-20 bout (rating of perceived exertion (RPE) = 15 vs 12, respectively, P < 0.05). Milk LA was significantly higher at 0 min following maximal exercise in the high and moderate CHO groups (1.27+/-0.56 and 1.52+/-0.49 mM, respectively) and following LAT exercise (0.19+/-0.16 and 0.25+/-0.12 mM, respectively), when compared with the control session (0.08+/-0.03 and 0.09+/-0.05 mM, respectively). This was not observed following the LAT-20 exercise in the high and moderate CHO groups (0.11+/-0.04 and 0.12+/-0.08 mM, respectively). Elevated milk LA persisted in the 30-min collection point after maximal exercise only. There was no significant effect of dietary treatment on milk or blood LA at any of the collection points. CONCLUSIONS: In lactating women whose caloric needs are being met: 1) dietary CHO intake, within a practical range, does not influence LA levels in breast milk at rest or after exercise; 2) LA appearance in the milk is a function of exercise intensity; and 3) moderate intensity exercise (RPE = 12) will not increase breast milk LA levels.