Andrew Masterson
Andrew Masterson is a former editor of Cosmos.
Breast-feeding for at least six months can reduce the subsequent risk of a woman developing type 2 diabetes by almost half, a new study has found.
The study, published in the journal JAMA Internal Medicine, followed the fortunes of 1238 US woman, black and white, enrolled in a longitudinal study called Coronary Artery Risk Development in Young Adults (CARDIA).
None of the women had suffered from diabetes before enrolling, nor did so before giving birth at least once over the subsequent 30 years. During that period, they were all regularly screened for diabetes, and reported lifestyle behaviours such as diet and exercise pursuits. Crucially, they also reported and whether they breast-fed their first child and, if so, for how long.
The surprising findings were uncovered by a team led by Erica Gunderson, a researcher employed by US private healthcare provider, Kaiser Permanente.
The data revealed that women who breast-fed for at least half a year carried a diabetes risk 47% lower than those who did not – and that the risk reduction continued across subsequent child-bearing years. Women who breast-fed for less than six months still enjoyed a 25% reduction in risk.{%recommended 6427%}
“We found a very strong association between breast-feeding duration and lower risk of developing diabetes, even after accounting for all possible confounding risk factors,” says Gunderson.
The finding adds to a growing body of evidence for the protective effects of breast-feeding for mothers. A 2014 Chinese study found that the practice cut ovarian cancer risk by 30%.
The year before, another study – using a smaller pool of participants – put the ovarian cancer risk reduction as high as 91%.
In Gunderson’s research, the degree of diabetes risk reduction was similar for black and white women – however, in line with higher health risks in other areas, black women were still three times as likely to develop the condition as their white counterparts. They were also less likely to breast-feed.
The exact reason for the apparently causal relationship between breast-feeding and diabetes risk remains unclear, but Gunderson’s paper ventures some plausible suggestions. For instance, hormones associated with lactation are known to influence the cells in the pancreas that control blood insulin levels and thus also influence blood sugar.
“We have known for a long time that breast-feeding has many benefits both for mothers and babies, however, previous evidence showed only weak effects on chronic disease in women,” says team member Tracy Flanagan.
“Now we see much stronger protection from this new study showing that mothers who breastfeed for months after their delivery, may be reducing their risk of developing type 2 diabetes by up to one half as they get older.”
She adds that the results should encourage doctors and other health professionals to strongly recommend a minimum half-year of breast-feeding to mums-to-be.
