Effects of diet and exercise on maternal body composition and breast milk components

Long-chain polyunsaturated fatty acids (LCPUFA) are essential for infant growth and development, and amounts in breast milk depend on maternal diet and body stores. Because exercise increases mobilization and utilization of fatty acids, maternal activity may also influence the amount of LCPUFA in breast milk. In addition, exercise has been shown to improve bone mineral density (BMD) in postmenopausal women. During lactation, bone turnover is elevated to provide calcium for breast milk. This results in decreased BMD.; Therefore, the purpose of these studies was to: (1) investigate the effects of diet and exercise on fatty acid concentrations in maternal plasma and breast milk, and (2) determine the effects of a specific resistance and aerobic training program and dietary intake on BMD and bone turnover during lactation.; In the first study, LCPUFA in plasma and breast milk were measured at 12 weeks postpartum in exercising and sedentary women. Dietary intake was recorded for three days. A subsample of women participated in exercise and rest sessions to examine the acute effects of exercise on breast milk LCPUFA. In the second study, whole body, lumbar spine (LS) and hip BMD and bone mineral content (BMC), and bone turnover markers were measured before and after a 16-wk intervention in breastfeeding women who either participated in a specific resistance and aerobic training program or were sedentary. Dietary intake and body composition were also assessed in all women.; In the first study, there were no differences in essential fatty acid intake between the two groups. Intake of linoleic acid (LA) was 11.05 +/- 1.39 and 9.34 +/- 0.97 and alpha-linolenic (LNA) was 0.96 +/- 0.12 and 0.82 +/- 0.09 grams/day for the sedentary and exercise groups, respectively. No differences were found in LCPUFA in plasma and breast milk between groups. After 30 minutes of exercise, there was a trend for an increase in LA and LNA. In the second study, exercising women lost significantly less LS BMD and LS BMC (p<0.05), and had substantial improvements in body composition. Calcium and protein intake were significant predictors of whole body BMD loss with parity being a significant covariate (p<0.05). Bone turnover markers were also significant predictors of LS BMD and LS BMC, when adjusted for parity and exercise (p<0.01).; These results suggest that women consuming adequate amounts of LCPUFA can exercise moderately without decreasing the LCPUFA in their breast milk. In addition, increased calcium and protein intake lessens BMD loss during lactation. In breastfeeding women, moderate resistance and aerobic exercise was effective in improving body composition and minimizing BMD losses.