Breastfeeding May Lower Risk of Diabetes

A woman nursing her baby
A woman nursing her baby
Findings may have implications for social policies to extend paid maternity leave to achieve higher intensity and longer duration of breastfeeding.

Woman who breastfeed may experience a significant long-term protective association between breastfeeding and the development of incident diabetes, regardless of factors such as metabolic status, obesity, and perinatal outcomes, with multiparous women at baseline experiencing the strongest association, according to a study published in JAMA Internal Medicine.

Researchers prospectively evaluated black (n=615) and white women (n=623) not diagnosed with diabetes at baseline and who had not given birth who were enrolled in the 30-year CARDIA (Coronary Artery Risk Development in Young Adults; Clinical identifier: NCT00005130) trial to examine the progression to diabetes in this group of women and its association with length of time breastfeeding.

Diabetes developed in a total of 182 women at an average of 47 years, demonstrating an incidence rate of 6.6 cases per 1000 years (95% CI, 5.6-7.6). Black women were found to have a higher incidence per 1000 person-years compared with white women (9.9; 95% CI, 8.2-11.6 and 3.5; 95% CI, 2.5-4.5, respectively [P for difference <.001]). Women with gestational diabetes (GD) were found to have a higher incidence of diabetes compared with women without GD (18.0; 95% CI, 13.3-22.8 and 5.1; 95% CI, 4.2-6.0, respectively [P for difference <.001]). The lowest incidence of diabetes in women with and without GD was found in women with lactation duration greater than 12 months, demonstrating an inverse relationship between lactation duration and diabetes incidence (Ptrend =.02).

During data analysis, researchers combined race and GD groups into a single Cox proportional hazards model in one analysis, and priori confounding variables were added in a second separate analysis. Both analyses still found that lactation duration was associated with a lower incidence of diabetes despite variables added (Ptrend <.001 and Ptrend =.01, respectively). Further, when time-dependent weight change was added, the protective association between lactation and incident diabetes was 25% to 47% lower (relative hazard 0.75-0.53; Ptrend =.01).

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After adjustment, women who breastfed for 0 to 6 months, for >6 months to <12 months, and for ≥12 months experienced the following relative hazard scores with 95% confidence intervals: 0.75 (95% CI, 0.51-1.09), 0.52 (95% CI, 0.31-0.87), and 0.53 (95% CI, 0.29-0.98), respectively, which demonstrates a significant risk reduction for women who breastfed for 6 or more months.

Researchers concluded that there was a strong association and an inverse relationship between lactation duration and incident diabetes in women of childbearing age. Further, women who breastfed for 6 months or more had a higher risk reduction (47%) compared with those who breastfed for less than 6 months (25%). The authors also suggested that these findings might have an impact on policy change to extend maternity leave and increase health care resource allocation to increase breastfeeding rates and duration. Clinicians should encourage mothers to breastfeed children for as long as they are able because of the significant benefits to both mother and baby that each successive month of breastfeeding provides.


Gunderson, EP, Lewis CE, Lin Y, et al. Lactation duration and progression to diabetes in women across the childbearing years: The 30-year CARDIA Study [published online January 16, 2018]. JAMA Intern Med. doi:10.1001/jamainternmed.2017.7978