So with all this running I’ve been doing it got me wondering if I am negatively affecting my milk supply and if my baby was still receiving adequate nourishment (I think I was just looking for reasons NOT to train for this half marathon). This led me to do some research! Yes, I know… of course I’m a nerd like that but I didn’t become an evidence-based practitioner for nothing…this is how we roll! So let me share with you bits and pieces of what I learned.
In summary, breastfeeding is not negatively affected by exercise whether it be prolonged cardiovascular exercise or moderate to high intensity training. There is some evidence that lactic acid levels increase if you feed your baby immediately after a high intensity workout (Carey & Quinn, 2001), which could cause a change in the taste of the milk but has no negative effects on the baby and most of the time they don’t notice. Even then, you would have to REALLY exert yourself to see this kind of change in milk composition.
In terms of milk supply, as long as adequate fluid and calorie intake is achieved exercise has no negative effect on milk supply (Dewy et al., 1994). This is what I was most worried about because after my long run last week I tried to pump afterwards and got very little! Which was stressful obviously! Of course I panicked, and then my husband reminded me that I just fed her before I left so it had only been a little over an hour and a half. Duh, that makes sense. Also, my own personal hypothesis is this… your body probably puts milk production on hold while exercising because it is using the energy for your muscles, BUT most likely makes up for it later in the day.
When the composition of breast milk was studied it was also found that there was no change in immune factors (such as SigA, lactoferrin, and lysozyme), major minerals (calcium, phosphorus, etc) and major nutrients (fat, protein, lactose) (Fly, Uhlin, Wallace, 1998).
I also found this to be super interesting ….
“ recreational athletes who performed an average of 88 minutes per day of aerobic exercise during the 6 months of breastfeeding had less body fat and produced a slightly greater quality and quantity of milk than postpartum non-exercising women” (Lovelady et al., 1990)
So pretty much because I am exercising I am producing higher quality and quantity of milk as well as reaping all the other benefits of postpartum exercise such as; decreased incidence of depression, decreased stress, improved mood and behaviour and increased weight loss. Guess this half- marathon training is paying off for everyone, including my baby & husband!
Now I have to add, after my quick literature review I did find there is definitely room for further research on the subject, a lot of the studies were from the 90’s and came from the same few researchers, but it’s just not a very highly studied topic so have to take what I could get!
So there is it, you can put your mind at rest…. breastfeeding and exercise are actually a good combo! Few things to remember…be sure to keep your fluid intake up, especially if it is a hot day out! It’s crucial to replace everything that you sweat out to avoid dehydration. I aim for 16 cups of water a day, and I usually have a coconut water or electrolyte beverage if it’s a day where I particularly sweat a lot. Also, losing 0.5-1lb a week while breastfeeding is perfectly healthy but you don’t want to lose too much weight too fast so be sure to replace some of the calories burned by exercise by having an extra snack afterwards.
In fitness & good health,
Carey GB, Quinn TJ 2001, Exercise and lactation: are they compatible? Can J Appl Phys 26(1): 55–74.
Dewy K, Lovelady C, Nommsen–Rivers L, McCrory M, Lonnerdal B 1994, A randomised study of the effects of aerobic exercise by lactating women on breast-milk volume and composition. New Engl J Med 330: 449–453.
Fly AD, Uhlin KL, Wallace JP 1998, Major mineral concentrations in human milk do not change after maximal exercise testing. Am J Clin Nutr 68(2):345–9.
Lovelady C, Lonnerdal B, Dewey K. Lactation performance of exercising women. Am J Clin Nutr. 1990;52:103–9.