Breastfeeding: Reduced risk of osteoporosis with nursing?

A friend recently posed the following question to me: A lactating woman does not produce estrogen in high levels. Because of the estrogen suppressing effects of breastfeeding, she cannot readily absorb calcium. Calcium is, however, always leaving her body in the milk she makes for her child. My friend suggests that suppressing estrogen for a year or more is likely to cause osteoporosis. I am nursing a three year old. Many Japanese mothers are given pressure to quit nursing after a year, and the above reason is cited. I've read just the opposite, that nursing can prevent osteoporosis. Who's right?

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Debbi Donovan

Debbi Donovan is a Board Certified Lactation Consultant, as well as a retired La Leche League Leader. For more than a decade, Debbi... Read more

During lactation a mother may experience decreases of bone mineral. A nursing mom's bone mineral density may be reduced in the whole body by one to two percent while she is still nursing. This is gained back, and bone mineral density may actually increase, when the baby is weaned from the breast. This is not dependant on additional calcium supplementation in the mother's diet. Breastfeeding has been shown to actually protect against osteoporosis (Blaauw, R. et al. Risk factors for development of osteoporosis in a South African population. SAMJ 1994; 84:328-32.)

Though it has been commonly believed that breastfeeding mothers need approximately 400 to 800 mg. more calcium in their daily diet, this theory had not been backed up by science. A study published in the August 1997 issue of the New England Journal of Medicine (NEJM) has found that breastfeeding mothers do not need extra calcium to help guard against bone loss (N Engl J Med 1997;337:523-8).

In an editorial in the same issue of the NEJM, Dr. Anne Prentice of the Medical Research Council states, "A picture is beginning to emerge showing that human lactation is associated with alterations in calcium metabolism, including the temporary mobilization and subsequent restitution of bone mineral, that are independent of dietary calcium intake and unresponsive to increases in calcium intake."

The Institute of Medicine's recommendations (August, 1997) also concur with the results of this study. They recommend that nursing mothers over the age of 18 consume 1,000 mg. of calcium daily -- the same as other adults.

These findings can help to assure the nursing mother that breastfeeding does not negatively impact bone mineral density, and seems in fact to decrease her chance of developing osteoporosis. Best wishes!

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