Duration breast-feeding linked to osteoporosis risk

NEW YORK (Reuters Health) - Postmenopausal women who spent longer periods of time breast-feeding their children may be at greater risk of developing osteoporosis, according to a new study.

Osteoporosis is a bone disease that occurs when bone tissue and bone density decrease significantly, leading to pain and increased risk of breaking a bone.

In a group of postmenopausal Mexican mestizo women -- those whose parents are of different races and thus have mixed genetic backgrounds -- researchers found that women who breast-fed their children for more than 36 months were twice as likely to get the disease as those who spent less time breast-feeding.

"One of the principal conclusions is the importance of considering the duration of breast-feeding as an important risk factor for osteoporosis," lead author Dr. Patricia Canto, of the National Medical Center in Mexico City, told Reuters Health in an e-mail.

Consistent with other studies, women who were 10 years past the onset of menopause were more than twice as likely to get osteoporosis as those closer to menopause, the investigators report in the journal Menopause.

A 1999 study showed that in the general population of Mexican women over 50 years old, 16 percent have osteoporosis. Of the 567 Mexican mestizo women who participated in the current study, 29 percent had osteoporosis, which could make the associations seen in the study appear stronger than they actually are in the general population.

As Canto explained, the study was not designed to show cause and effect, but instead was intended to show associations of certain risk factors with the disease.

Also concerning to the authors is that Mexican women, on average, have 2 or more children, and around 67 percent of Mexican women exclusively breast-feed their children, which they believe could lead more women to develop osteoporosis.

To help reduce the potential risk, the World Health Organization and United Nations Children's Fund recommend that "infants should be exclusively breastfed for the first six months of life...(and should then) receive nutritionally adequate and safe complementary foods while breastfeeding continues for up to two years of age or beyond."

Despite these recommendations, some women may not have access to these foods and formulas. Going by food costs in Mexico, a little more than 18 percent of the Mexican population lives below the poverty line, according to the CIA's World Factbook. For women in these poor communities, breast-feeding may be the only option to nourish their children.

Though the association between osteoporosis and breast-feeding was significant in the study, Dr. Patricia Clark, of the Children's Hospital of Mexico in Mexico City, said that many other studies have found no association between breast-feeding and osteoporosis, making it difficult to draw any conclusions.

"It's a very controversial topic," Clark told Reuters Health. "I don't think women who breast feed and have a lot of children should be particularly worried they'll get osteoporosis."

She explained that during pregnancy and breast-feeding periods, there is a decrease in calcium levels, but that this normally balances out afterwards.

"I would just recommend that women maintain good nutrition and exercise during pregnancy and breast-feeding," she added.

SOURCE: link.reuters.com/wed48p Menopause, September 27, 2010.