Breastfeeding for long periods protects kids from obesity and stuttering—while guarding their moms from breast cancer, recent studies claim.

If proven true in follow-up work, these studies—added to an earlier finding that breast- feeding wards off Alzheimer’s—may have women around the world pitching their baby bottles and going au naturel on the subway.

The largest of the studies, published in an August Journal of the American Medical Association Pediatrics, examined 43,367 Japanese children, born after 37 gestational weeks, for obesity. It has long been postulated that breastfeeding protects against childhood obesity. But evidence has remained elusive, partly due to socio-economic status complications. Additionally, most children studied have lived in Western nations.

In the present study, researchers looked for low weight, normal weight, overweight, and obesity using body mass index in 7 and 8 year old Japanese children.

The study was run by Michiyo Yamakawa, M.H.Sc., of the Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences. She found that, after adjusting for child factors of sex, TV time, and computer game time, and maternal factors of education level, smoking status, and work, exclusive breastfeeding for 6 to 7 months resulted in children who were 45 percent less obese than children fed formula. The reasons, says Yamakawa, contacted via email, may be many. "First, breastfed infants may have more discretion over the amount of milk they consume than those fed with infant formula, which could lead to better self-regulation of energy intake in later life. Second, breast milk contains hormones such as leptin, ghrelin, and adiponectin, which may positively affect body fat deposition. Third, infant formula contains more protein than breast milk, which may result in increased adiposity and weight gain in the formula-fed."

Meanwhile, in an August Journal of Clinical Nursing study, the team of Emilio González-Jiménez of the University of Granada in Spain examined medical records of 504 female patients who were 19 to 91 years of age, and who had been diagnosed and treated for breast cancer from 2004 to 2009 at a single hospital. That study found that breastfeeding for more than six months seemed to protect nonsmoking mothers against breast cancer. The team looked at factors including age at diagnosis, how long the women breastfed, family history of cancer, obesity, alcohol consumption, and smoking habits.

Women who breastfed for at least six months were diagnosed with breast cancer at a later age, regardless of family cancer history. Nonsmokers who breastfed for longer than six months were diagnosed with breast cancer an average of 10 years later than nonsmokers who breastfed for shorter periods. By contrast, female smokers were diagnosed with breast cancer at a younger age and didn’t benefit from longer breastfeeding stints.

The reduction in breast cancer may have to do with breast stem cell turnover. When women are undergoing monthly cycles, their breast stem cells are constantly replicating, growing, dying—and starting all over again. Such constant activity can result in genetic mutations that can eventually result in cancer. When women are breast feeding, their breasts are in a more stable state and the constant cycling is postponed, minimizing chances for genetic mutations.

Nicoline Grinager Ambrose, PhD, Associate Professor, Department of Speech and Hearing Science, College of Applied Health Sciences, University of Illinois

Finally, an August Journal of Communication Disorders study conducted by University of Illinois researchers found that, among 47 children who stuttered at an early age, those who were breastfed were more likely to recover.

Seeing the greatest benefit were boys, more of whom stutter. Boys who were breast-fed for more than a year stood one-sixth the chance of becoming persistent stutterers than boys who weren’t breast-fed. Neither income nor maternal education influenced stuttering, according to speech professor emerita Nicoline Ambrose and doctoral student Jamie Mahurin-Smith. There was no indication of underlying neurological problems.

Maurin-Smith came up with the idea after reading still more papers describing the varied wonders of breast-feeding." I first had the idea for the study when I was learning about the effects of breastfeeding," says Mahurin-Smith, a lactation consultant and speech-language pathologist, also contacted via email. "Breastfeeding and bed-wetting? Breastfeeding and schizophrenia? Who knew? We don't know a lot about environmental variables that influence stuttering persistence/recovery, and breastfeeding seemed like an intriguing possibility."

Jamie Mahurin Smith, PhD, CCC-SLP, Illinois State UniversityAmbrose and Mahurin-Smith do have educated guesses. They speculate essential fatty acids in breast milk, often lacking in formula, are a key.  "Long-chain fatty acids found in human milk, specifically docosahexaenoic acid and arachidonic acid, play an important role in the development of neural tissue," Mahurin-Smith said in a prepared statement. "Fluent speech requires an extraordinarily complex sequence of events to unfold rapidly, and our hypothesis was that early differences in neurodevelopment could cause difficulties with speech fluency later in life."

The infant brain triples in size its first year. "More than half of the solid weight of that newly built tissue will be lipid," the researchers wrote. DHA is the mammalian brain’s most prevalent fatty acid. Infants lacking proper diet DHA can create it from other fatty acids, but "research shows that the rate at which DHA is incorporated into brain tissue outstrips the rate at which it can be synthesized."

Much research has indicated that the lack of proper DHA in development can affect brain structure and function. Fatty acids can also impact gene expression, binding to transcription factors that can regulate gene activity. "It may be that fatty acid intake affects the expression of genes responsible for stuttering," Ambrose’s statement read.