Breastfeeding may reduce a woman’s risk of developing diabetes, with a prospective cohort study showing a strong, inverse association between lactation duration and risk of diabetes.

In a report published in the Jan. 16 online edition of JAMA Internal Medicine, researchers analyzed data from the Coronary Artery Risk Development Study in Young Adults (CARDIA), which followed 1,238 women aged 18-30 for 30 years, with multiple assessments of glucose tolerance over the course of the study.

The analysis revealed that women who breastfed for at least 12 months had a 47% lower relative risk of developing diabetes during the study, compared with women who did not breastfeed at all (95% confidence interval, 0.29-0.98). This was after adjustment for potential confounders such as race, gestational diabetes status, parity, body mass index, family history of diabetes, physical activity, and weight change.

Women who breastfed for 6-12 months had a 48% reduction in the risk of diabetes (95% CI, 0.31-0.87), and those who breastfed for up to 6 months had a 25% lower risk (95% CI, 0.51-1.09), with the trend being significant.

In women with a history of gestational diabetes, those who did not breastfeed at all had a 2.08% higher excess risk of incident diabetes per year, compared with women who breastfed for at least 12 months. The increase in excess risk for the same comparison in women without a history of gestational diabetes was 0.48% per year.

Erica P. Gunderson, PhD, of Kaiser Permanente Northern California, Oakland, and her coauthors noted that previous meta-analyses of the effect of lactation on diabetes incidence or prevalence pointed to protective summary estimates of 9%-11% per year of lactation.

“Lactating women have lower circulating glucose in both fasting and post absorptive states, as well as lower insulin secretion, despite increased glucose production rates,” the authors wrote. “About 50 g of glucose per 24 hours is diverted into the mammary gland for milk synthesis via non–insulin mediated pathways.”

Studies in mice have also suggested that lactating animals have greater pancreatic beta-cell proliferation.

While the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists recommend breastfeeding for 1 year, only 55% of women in the United States are still breastfeeding at 6 months and 33% are still breastfeeding at 1 year after birth. Black women are also less likely to breastfeed, regardless of socioeconomic status or body size.

“Lactation is a natural biological process with the enormous potential to provide long-term benefits to maternal health, but has been underappreciated as a potential key strategy for early primary prevention of metabolic diseases in women across the childbearing years and beyond.”

The study and analyses were supported by the National Institute of Diabetes and Digestive and Kidney Diseases, and two authors declared funding from pharmaceutical companies.

SOURCE: JAMA Intern Med. 2016 Jan 16. doi: 10.1001/jamainternmed.2017.7978 .


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