Tuesday, June 21, 2011

The Active Mommy Conundrum: Can Exercise Harm Breastfeeding? Part I

By Taryn Barrette, RD and Jane Heinig

I don’t have children yet, but I’ve always imagined that one of my favorite things to do with my new baby would be to take him for a jog. I lead a pretty active lifestyle and feel that it is important to share my love for fitness with my children – but I also plan to breastfeed and I was concerned about the potential for exercise to affect my milk supply. I had also heard that lactic acid can build up in breast milk.

So, I began to wonder: Does exercise reduce milk supply? Does exercise lead to lactic acid in breast milk? And if so, can the baby actually taste it? If lactic acid is present in the milk, will the baby refuse to drink it? How am I ever going to be the active mommy that I’ve always dreamed of? In today’s post, we will discuss the effect of exercise on breast milk volume. Next time, we’ll talk about breast milk and lactic acid.

Exercise and Breast Milk Volume

In many countries around the world, the idea that physical activity would interfere with breastfeeding would be considered crazy or a joke. Most women in the world must maintain very active lives despite having young children in tow. Many women have physically demanding occupations and many more must walk great distances for food or water. Women with access to their children (not separated for many hours with no way to express their milk) are able to breastfeed despite their activity levels. The challenge comes when a woman’s occupation prevents her from being able to feed her baby. Her body will make less milk if less milk is removed. But exercising, especially in short to medium bouts, even at very high levels does not reduce milk supply. A series of important studies looking at this phenomenon where conducted here, at UC Davis. In the first of the studies, the researchers followed small groups of women who were either sedentary or extremely active (marathoners, masters swimmers, triathletes) and they found no difference in the women’s milk supply or in their infants’ growth. In fact, they found that the athletes tended to have higher milk volumes and greater energy content in their milk. In a follow-up study, the researchers took a group of sedentary women and increased their activity by putting them on a supervised exercise program (some of these women were also put on low-calorie diets). Once again, they found that there was no effect of the exercise on the mothers’ milk supply or their infants’ growth. Other studies have indicated that exercise did not interfere with lactation among women who were overweight when they began exercising. All of this research shows that going out for a jog (when you’re ready and the doctor says it’s ok) is a great idea!


Lovelady CA, Lonnerdal B, Dewey KG. Lactation performance of exercising women.Am J Clin Nutr. 1990 Jul;52(1):103-9.

Lovelady CA, Garner KE, Moreno KL, Williams JP. The effect of weight loss in overweight, lactating women on the growth of their infants. N Engl J Med. 2000 Feb 17;342(7):449-53.

Lovelady CA, Nommsen-Rivers LA, McCrory MA, Dewey KG. Effects of exercise on plasma lipids and metabolism of lactating women. Med Sci Sports Exerc. 1995 Jan;27(1):22-8.


  1. I just read your blog for the first time, today. I was interested to see the research. I have three children, breastfed exclusively for 6 months each, and breastfed with solid food until about 2.5 years old. I also exercised daily during pregnancy and resumed after 4 weeks including jogging. My kids were all fat and healthy, and I lost every pound within 2 weeks post-partum. I always wondered when activity was discouraged, thinking about how sedentary motherhood is largely a wealthy western phenomena. Glad to see the results of the study you shared. Thank you!

  2. Respectfully, I disagree. When I was exclusively nursing my son, I began aerobic walking (maintained a healthy diet) and my supply dropped drastically, to the point where I had to use galactogogues. When I stopped exercising, my milk supply increased. After a month, I tried exercising, and my supply dropped again. Once I stopped, supply went back up. I decided I'd rather nurse my son than actively lose weight, so that's what I did. Naturally, I find this research interesting, because I now wonder what influenced my milk supply if it wasn't exercise.
    - Taylor (http://tardismama.wordpress.com)

  3. Interesting! We certainly don't believe that research findings apply to everyone. It would be fascinating to know what was happening in your case. Thanks for sharing.

  4. I recently joined a gym and the nutritionist/personal trainer there said I should avoid weight lifting do to acid/toxins that would wind up in the milk. Was this advice false?

  5. when you become dehydrated you produce less milk. I would think that maybe even if you increased your water intake you didn't do it enough and became dehydrated, decreasing your supply.