Moderate levels of exercise do not appear to affect milk production or impair infant growth.[1][2][3] However, intense or exhaustive exercise may temporarily alter milk composition (e.g., increased lactic acid and decreased secretory IgA concentrations), but milk composition usually returns to baseline within one hour postexercise. Moreover, infants can safely drink milk produced immediately postexercise despite the change in composition.[4]
How does physical activity affect lactation?
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•Last Updated: May 16, 2025
Moderate exercise does not affect milk production or infant growth, but intense exercise may temporarily change milk composition, such as increasing lactic acid and decreasing secretory IgA levels, though these changes revert to baseline within an hour. Infants can safely consume milk produced immediately after intense exercise despite these temporary alterations.