TUESDAY, Feb. 4, 2003 (HealthDayNews) -- New moms can stop worrying: Thirty minutes on a treadmill won't deprive your baby of essential ingredients in your breast milk.
A study published in the February issue of Pediatrics concludes that moderate exercise doesn't affect levels of three key immunity-building components in breast milk.
Researchers at the University of North Carolina at Greensboro say the findings should ease concerns among women that arose after a widely publicized 1998 study warned that strenuous exercise reduced a vital antibody in breast milk.
"The popular press really picked up on that study," says Cheryl A. Lovelady, author of the new study. "Whenever I'd go to speak on exercise, people would say, 'What about the antibodies?' "
The 1998 study, by Indiana University researchers, had reported that tests of breast milk 10 minutes and 30 minutes after a mother exercised heavily showed significant reductions in immunoglobulin A (IgA), which protects against viruses and bacteria.
However, that study found IgA levels rebounded to nearly normal levels an hour after exercise.
The North Carolina researchers say the 1998 study results had been based on IgA tests given after the women "exercised until exhaustion."
By contrast, the new study tested levels of IgA and other beneficial substances in breast milk after moderate exercise -- and yielded unequivocal results.
"The most important conclusion is moms can embark on a moderate exercise program and not be concerned about it affecting the composition of their breast milk," Lovelady says.
In the latest study, 17 women who were regular exercisers gave samples of their breast milk before a workout. They then completed moderate, 30-minute sessions on a treadmill -- at about 75 percent of maximum heart rate -- and gave breast milk samples 10 minutes and 60 minutes later.
The exercise did not affect levels of IgA or two key bacteria-fighters: the protein lactoferrin and the enzyme lysozyme. In addition, concentrations of the three compounds were similar in the breast milk of the women who exercised regularly and a control group of sedentary women.
Researchers measured these three compounds because they're among the most important among 200 in breast milk and they appear in large enough concentrations to measure, says Lovelady, an associate professor of nutrition.
The study did not look at the effects of more strenuous exercise. "We still don't know about extreme exercise, so that's not what we recommend," Lovelady says.
Moderate exercise, she says, improves the mother's cardiovascular system and immune system, among other things. However, too much or too little exercise can lower immune system function, she adds.
Lovelady stresses the importance of a well-balanced diet among breast-feeding women. And she recommends those not in the habit of exercising wait at least a month after giving birth to start exercise, and then they should begin gradually.
Dr. Lawrence M. Gartner, chairman of the executive committee of the breast-feeding section of the American Academy of Pediatrics, says the study's findings reinforce his belief in the value of moderate exercise for nursing mothers.
"I did not think moderate exercise had any detrimental effect on any aspect of breast-feeding," Gartner says.
However, like Lovelady, he adds the effects of extreme exercise on breast-feeding remain uncertain.
The study's results should come as welcome news to many women, at a time when breast-feeding has reached a record high in the United States.
More women are starting to breast-feed soon after giving birth and more are continuing to nurse their infants to six months of age, according to a recent survey by the Ross Products division of Abbott Laboratories, a maker of infant formula.
About seven of 10 new mothers started breast-feeding in 2001, and about one-third continued to nurse at six months -- the highest percentages documented by the company since it started surveying breast-feeding practices in 1954.
More information
For more on breast-feeding, visit the American Academy of Pediatrics or the
La Leche League International.
