Middle-aged and older women who breastfed their children may have a lower risk of developing type 2 diabetes than those who bottle-fed, a new study suggests.

Australian researchers found that among more than 53,000 women age 45 and older, the odds of having diabetes were similar for women with children and those who had remained childless. But among women with children, each year of breastfeeding was associated with a 14 percent reduction in diabetes risk.

The findings, published in the journal Diabetes Care, do not prove that breastfeeding itself is somehow protective against type 2 diabetes later in life.

But they are in line with several past studies that have linked breastfeeding to a similar reduction in diabetes risk compared with bottle-feeding, according to lead researcher Dr. Bette Liu, of the University of Western Sydney.

What’s new here, she told Reuters Health in an email, is that the study also included women who had never had children. And compared with these women, women who’d had children and never breastfed were 50 percent more likely to have type 2 diabetes.

In contrast, the risk was not elevated among women who had breastfed each of their children for at least three months.

“In other words,” Liu said, “it appears that having children increases the chances of women developing type 2 diabetes in later life, but breastfeeding can reduce this risk to the same level as that of women who have never had children.”

The study included 53,726 women who completed questionnaires on various health and lifestyle factors. Of 5,700 women who had never had children, 274 - or roughly 5 percent - said they had been diagnosed with diabetes. Similarly, diabetes was reported by 5 percent of the 25,000-plus women who had breastfed each child for more than three months.

Meanwhile, of the 6,171 women who’d had children but never breastfed, 591 - or 9.5 percent - reported a diabetes diagnosis. And among the 15,400 women who’d breastfed each of their children for three months or less, just under 7 percent said they had diabetes.

The researchers then weighed a number of other factors that could affect a woman’s likelihood of breastfeeding and/or developing diabetes - including age, weight, family history of diabetes, reported exercise habits and education and income levels.

Breastfeeding itself remained linked to the odds of having diabetes, the investigators say.

For any one woman, Liu said, the likelihood of developing type 2 diabetes depends on a range of factors. Some major risk factors - like age (the risk climbs after age 45), family history and race (black and Hispanic adults have higher risks than whites) - are unchangeable; but some others, like excess weight, are controllable.

If breastfeeding is a factor, that would be important, Liu said, because it’s something women can choose.

It’s not clear why breastfeeding might affect a woman’s later risk of type 2 diabetes. Liu speculated that the hormonal changes that come with breastfeeding may have lasting effects on how a woman’s body processes blood sugar.

For now, Liu said the current findings suggest that lower long-term diabetes risk may stand as an additional benefit of breastfeeding.

“I would say to women considering breastfeeding that there are benefits not only for the health of their babies but also for their own longer-term health,” she said.

SOURCE: Diabetes Care, online March 23, 2010.