Breastfed babies may be less likely to develop type 2 diabetes, according to a new study.

The analysis suggests as many as one in 20 cases of type 2 diabetes seen in industrialized nations could be attributable to formula feeding.

When seven studies involving almost 77,000 people were combined, breastfeeding appeared to lower diabetes risk by roughly 39 percent, according to researcher Christopher G. Owen, PhD.

The analysis is published in the latest issue of the American Journal of Clinical Nutrition.

“Breastfeeding in infancy is associated with a reduced risk of type 2 diabetes,” Owen tells WebMD. “Whether this effect is attributed to a difference in the content of breast milk compared to (commercial) formula, or whether the family environment and nurture of breastfed infants is the cause remains to be established.”

More Than 1 Million Cases a Year

The number of middle-aged Americans with type 2 diabetes has doubled over the last 30 years; similar increases are being seen throughout the developed world.

In 2004, about 1.4 million U.S. adults aged 18 to 79 were diagnosed with type 2 diabetes.

Though obesity is the single biggest cause of the disease, there is increasing speculation that early-life nutrition may play a role in disease risk later in life.

Studies assessing the impact of breastfeeding on diabetes risk have been inconsistent, with some finding a protective benefit and others finding little benefit.

In an effort to better understand the role of breastfeeding in later-life diabetes, Owen and colleagues from the University of London conducted a systematic review of the published research.

Twenty-three studies examining the impact of infant feeding on later type 2 diabetes risk were identified.

Seven Studies Reviewed

When the seven studies that dealt directly with the issue were combined, the researchers concluded that breastfeeding lowered diabetes risk by as little as 15% and as much as 56%.

Using the most conservative risk reduction estimate of 15%, the researchers concluded that 5% of type 2 diabetes cases occurring in the Western world may be attributable to formula feeding.

“Although this effect is important, it is modest compared with the population benefits of reducing overweight and obesity later in life,” Owen says.

More Study Needed

He adds that more study is needed to confirm the disease/breastfeeding link.

The impact of breastfeeding duration also remains unknown. And it is not clear if breastfeeding is independently protective against diabetes or if the protection is due to its role in reducing the risk of obesity.

Other studies have shown breastfed babies are less likely than formula-fed babies to become overweight children and adults.

In a recent study of more than 15,000 children, researchers reported this was true even of children at high risk because their mothers were obese or had diabetes.

The American Academy of Pediatrics (AAP) recommends exclusive breastfeeding during the first six months of life and urges mothers to continue breastfeeding for the baby’s first year.

University of Rochester professor of pediatrics Ruth Lawrence, MD, who helped write the AAP guidelines, says published studies may actually underestimate breastfeeding’s impact on childhood and adult obesity.

“Babies who are exclusively breastfed seem to have a big advantage,” she says. “There is not one single study suggesting that formula is better than breast milk.”

By Salynn Boyles, reviewed By Louise Chang, MD

SOURCES: Owen, C., American Journal of Clinical Nutrition, 2006; vol 84: pp 1043-1054. Christopher G. Owen, PhD, senior lecturer in epidemiology, St George’s, University of London. Elizabeth Mayer-Davis, PhD, professor of epidemiology, University of South Carolina, Columbia; director, Center for Research in Nutrition and Health Disparities, Arnold School of Public Health, University of South Carolina. Ruth Lawrence, MD, professor of pediatrics, University of Rochester, Rochester, N.Y. WebMD Medical News: “Breastfed Babies Less Overweight.”