Research has shown that moderate exercise does not affect milk supply, milk composition, or baby’s growth. Exercising to exhaustion may have a short-term effect on lactic acid and IgA content of a mother’s milk.
Does exercise affect milk supply or nutrient content?
No. Studies have shown no difference in milk production or nutrient composition or babies’ weight gain. One study showed a slight increase in milk supply for the women who exercised regularly, but because of the small size of the study this increase may not be significant.
Does exercise affect immunologic factors in milk?
A couple of small studies have shown that there is no difference in immunologic factors after moderate exercise, but that IgA levels are decreased short-term after exhaustive exercise. Most breastfeeding mothers do not exercise to exhaustion, but for those that do so and breastfeed soon after, a decrease in IgA levels in one feeding per day is unlikely to be significant.
In 1997, a study by Gregory et al found that IgA levels in breastmilk were decreased for a short time (10-30 minutes) after mom had exercised strenuously (“exhaustive exercise”), but that levels had returned to normal within an hour. They also observed that IgA levels increased after the breast had been emptied, whether or not mom had been exercising strenuously. In 2003, Lovelady et al looked at immunologic factors (IgA, lactoferrin, lysozyme) in breastmilk after moderate exercise, and found no difference in the milk of exercising and non-exercising mothers.
Does lactic acid increase in breastmilk after exercise?
Research has not shown a noticeable increase in lactic acid buildup after moderate exercise (50% & 75% intensity). The lactic acid in breastmilk does increase somewhat if mom exercises to maximum (100%) intensity, also described as exhaustive exercise. This increase may be present up to 90 minutes post-exercise. There are no known harmful effects for the baby.
Will baby refuse the breast after mom exercises?
Most studies have found no difference in acceptance of the breast, even after maximum intensity exercise.
Although a highly publicized 1992 study indicated that baby might fuss or refuse expressed milk from a mom who had been exercising at 100% intensity, the results were questionable because the babies were fed the milk by dropper (unfamiliar to these babies), and the mothers reported that the babies had not had problems with nursing after exercise in the past. A more recent study showed no change in infants’ acceptable of mom’s milk an hour after exercise, even for the moms who exercised at maximum intensity (and thus did have a slight increase in lactic acid in their milk).
If baby seems to object to the taste of mom’s milk after strenuous exercise, keep in mind that it might have nothing to do with the exercise – baby might be distracted or objecting to the salty taste of sweat on your breast, etc. If this happens consistently, mom might try expressing a little milk (3-5 mL from each breast) before nursing baby, postponing feeding for a half hour to let the lactic acid levels subside, and/or decreasing workout intensity a bit in the future.
CARiFiT top tips for breastfeeding mums!
For your own comfort, you may wish to feed baby before exercising, you will be more comfortable and baby will be satisfied so your workout is far more liekly to go to plan and without disruption and discomfort.
Some babies don’t like feeding when mom has been sweating (due to the salt on mom’s skin) so you may wish to rinse your breasts or take a shower before they feed again.
If you regularly lift weights or do other exercises involving repetitive arm movement and you develop plugged ducts, cut back and start again more slowly.
Keep yourself well hydrated before, during and after your workouts!