The Effect of Physical Activity on Human Milk Macronutrient Content and Its Volume

Objective: There are multiple health benefits associated with both breastfeeding and practicing physical activity (PA). Therefore, it is likely that many women might want to engage in both. We designed the current randomized clinical trial to examine the effect of moderate- to high-intensity PA on human milk (HM) volume and macronutrient contents. Methods and Study Design: In this prospective, randomized, crossover clinical trial, we recruited 31 healthy mothers who had been exclusively breastfeeding their infants. Mothers expressed HM twice each day on 2 consecutive days - a day with PA (1-hour before and 1-hour after PA) and a control day without PA (at the exact same hours of the day). The order of days (with/without PA) was determined randomly. Macronutrients and energy contents of HM were analyzed using the Human Milk Analyzer (Miris AB, Uppsala, Sweden). PA was graded according to the Borg Rating of Perceived Exertion scale (RPE scale). Results: A total 124 HM samples from 31 mothers were analyzed. Moderate- to high-intensity PA affected neither macronutrients (fat, carbohydrates, protein) nor energy content. Milk volume remained unaffected by PA as well. Conclusions: Maternal PA does not affect HM volume or its macronutrient contents. Lactating mothers can be reassured regarding their breast milk volume and composition while practicing PA of moderate to high intensity.