Exercise and Breastfeeding

By Mary Bibb, BA, IBCLC

Exercise is good for everyone, including breastfeeding mothers. Mothers who exercise have healthier hearts and tend to feel happier than those who don’t.   Breastfeeding and exercise reduce stress and help to protect against depression.  Mothers who exercise while dieting lose fat and not muscle. Exercise does not decrease milk supply. Babies whose mothers exercise gain as much weight as babies whose mothers who do not exercise.

Some mothers may have heard that exercise will make milk “sour.” Milk does not become unsafe in the breast, even if the mom gets hot or works hard. There is more lactic acid (a harmless substance that muscles make during exercise) in milk when mothers exercise strenuously. Exercising moderately does not increase lactic acid levels in milk.  Very intense exercise does increase the amount of lactic acid in the milk, but this does not make the baby unwilling to breastfeed or take the milk from a bottle.  Lactic acid disappears from milk quickly even after heavy exercise.

Exercise may be uncomfortable for some women if their breasts are full.  Many women athletes find that exercise is more comfortable when they wear a supportive bra and feed the baby or pump beforehand.

Reviewed by Barbara Wilson-Clay, BSEd, IBCLC 


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