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Just as the benefits of breast feeding are well documented so are the benefits of post natal exercise. During this time, facilitating a women’s return to her pre-pregnancy weight is a key element for her overall health and well being. For breast feeding women there is often a concern that the presence of lactic acid in the breast milk following exercise can result in infant rejection. There is also a concern that lactation may be compromised by rapid weight loss. Previous research, conducted by Wallace et al, has reported that breast milk lactic acid levels increase after lactating women complete a bout of exhaustive exercise, resulting in poor infant acceptance of the post exercise breast milk. However, this study consisted of exercise to exhaustion and the results may not be applicable to women who exercise at a moderate intensity level. Recent research has looked more closely at the compatibility of exercise and lactation. It has been found that infant acceptance of expressed breast milk is the same one hour before and one hour after maternal exercise at both moderate and maximal intensities. These results persisted despite a small but significant increase in breast milk lactic acid one hour after maximal exercise compared with one hour before. (Wright et al) Interestingly, another study by Lovelady et al, which looked at the immunological components in breast milk, has demonstrated that moderate exercise during lactation doesn’t affect the immunological enzymes in breast milk. These enzymes are responsible for providing immunity to the infant. There have been reports suggesting these enzyme levels in breast milk are lower after exercise but again, the women reported exercised until exhaustion. It is now widely accepted that during moderate exercise, stress hormones, which can suppress immunity, are not elevated to the same extent as during prolonged or heavy exertion. Moderate exercise has no effect on the immunologic components of breast milk. Concerns that rapid weight loss may compromise lactation have also been address of late. As a guideline, moderate weight loss (< 2kg/month) appears to be compatible with lactation. (Dewey, KG) Lactating women who exercise retain less weight from pregnancy, have higher energy expenditure and have better measures of psychosocial well being. Regular moderate exercise will not cause lactic acid to build up in your system. Unless exercise intensity is very high, there is little change in lactate levels or immunological components in breast milk. Women can therefore enjoy the benefits of exercise (provided there are no contraindications) while breast feeding. References Dewey, KG. (1998). Maternal Composition, Caloric Restriction and Exercise during Lactation. An overview. J. Nutr. Feb 128: 3795. Dewey, KG., Lovelady, CA., Nommsen-Rivers, LA., McCrory, MA., Lonnerdal, B. (1994). A Randomized Study of the Effects of Aerobic Exercise by Lactating Women on Breast Milk Volume and Composition. N Engl J Med. Feb 17;330(7): 449-53. Lovelady, CA., Hunter, CP., Geigerman, C. (2003). Effects of Exercise on Immunologic Factors in Breast Milk. Pediatrics. 111: e148-e152. Wright, KS., Quinn, TJ., Carey, GB.(2002). Infant Acceptance of Breast Milk After Maternal Exercise. Pediatrics. 109: 585-589.
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