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“Tit Bits” series: Exercise and Lactation… the ins and outs of working out throughout the ages

Updated: Aug 8, 2023

Throughout my “Tit Bits” series (subscribe to my email list to receive these!), I want to share how breastfeeding advice changes era to era, country to country, and even region to region and family to family; and how young the field of lactation consulting is for such a vital thing that has been going on since mammals originated.

A little back story…

In 1825, the good doctor, Dr. Dewees (a renowned physician who focused on lactation and breastfeeding), cautioned the lactating against "ruining the milk” by moving too vigorously. "Running, walking too fast, or dancing, should be carefully avoided; especially as much injury is done the child by its receiving the milk, after such violence has been offered the circulatory system. But should accident, necessity, or inattention, place the system in the situation just mentioned, the child must be withheld from the breast for at least two hours after the occurrence; and then the milk which was present in the breast at that time must not be offered it—it must be drawn off by some other means and thrown away." (Page 87-88, Rule #270-271.)

…we know he was doing his best… but doc! No exercising while breastfeeding?! What’s a parent to do?

So…here's what we know in modern times about exercising and lactating:

Research consistently shows there is no reason to abstain from exercise while lactating. Whew! The macronutrient (fat/carbs/protein) composition and the volume of the milk are not impacted by exercise. The most common obstacle, as you probably already could guess, is finding the time.

Although moderate exercise is incredibly beneficial for overall physical and mental health, exercising with VERY HIGH-INTENSITY, however, could cause some issues such as:

-reduction in supply (from burning a LOT more calories than you are replacing, and not re-hydrating).

-sore nipples from excessive friction against nipples (running/jogging) – try running AFTER nursing or pumping and using nipple ointment to reduce friction (those soft bamboo nursing pads are nice, too).

-refusal to breastfeed due to salty taste of sweaty skin

-temporary rise in milk lactate (lactic acid), which has a sour/bitter taste (as opposed to the sweet taste baby is used to).

So what’s the skinny on lactic acid?… besides those sore muscles after leg day?

Lactic acid is a chemical your body produces when your body uses carbohydrates for energy. Anything that causes your body to use more oxygen than usual (exercise, loss of blood, racing heart) can cause lactic acid to increase in your bloodstream. As it rises in your blood, it passes right into your breastmilk. Studies have shown that lactic acid can peak in the breastmilk 10 minutes (with women exercising with full breasts) or 30 minutes (with women exercising with "empty" breasts) after exercising, and can take 90 minutes to clear completely.

Using a double-blind sample of milk taken before exercising and 10 and 30 minutes after exercising, researchers delivered the milk via medicine dropper to infants (breasts wiped clean before expressing her sample). Babies were LESS likely to accept the higher lactic acid milk (human adults could even taste the difference of the more bitter/sour high-lactic-acid milk). Babies showed signs of puckering and refusal with the higher lactic acid milk (babies can show signs of puckering with sour things even at a few hours of age!).

Will every baby reject milk after you exercise? No. Some babies will also take milk high in lipase (which really tastes and smells bad, but is NOT dangerous to them)—and some babies are more picky about their cuisine. So, if you notice a pattern that baby is more picky after you do high-intensity exercise, you could try these things to reduce your lactic acid:

-deep breaths during exercise

-decrease of exercise intensity

-low-intensity movements after working out (walking, foam rolling, yoga)

-pump before exercising and offer breast (or pump) more than 90 min afterward

As you gradually work up in your intensity of workout, your body will acclimate and this lactic acid won't build up as much.

Thanks Doc!

So, although I'm sure Dr Dewees did not know the science behind WHY some babies reject the breastmilk after a mother has vigorously moved her body, he was a good scientist by NOTICING that something was amiss and correlated—and did his best to advise families on how to handle things. I sure wish he were alive today to sit down and talk about all of this—I think he'd be fascinated.

Whether you exercise or not, are breastfeeding or bottle feeding, remember how amazing you are each day.

Stay awesome, Mama!

Kelly Wysocki-Emery


Founder of baby beloved inc.

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