A reader recently asked whether exercise — 
specifically marathon training — affects lactation and breastfeeding. I did a little digging and came up with some information, but decided the article fit better at another site for which I write: Trail and Ultra Running. Here’s a brief summary of my findings, based upon the current research:
- Moderate exercise (about 45 min/day, 5 days/week, moderate intensity) probably has no negative effect on milk production
- Short-term vigorous exercise probably has no negative impact on milk production
- Habitual moderate-volume exercisers may make slightly more milk than sedentary women
- Exercise that results in short-term (~2 weeks) significant caloric deficit probably has no negative effect on milk production
- There’s no evidence that habitual moderate exercise negatively impacts nutritional content of milk or immunologic factors (like antibodies)
- Moderate exercise doesn’t appear to increase the amount of lactic acid (a waste product of exercise) in milk, while intense exercise increases lactic acid in milk for about 90 minutes; this doesn’t affect nutrition, but may impact flavor
- Infants may or may not respond negatively to temporarily increased levels of lactic acid in milk; women can pump before exercising if this is a concern
- Lactic acid clears from the milk as it clears from the blood; there’s no need to “pump and dump” after vigorous exercise
Read the entire post here.
