Breastfeeding Can Prevent Diabetes Development

Study shows that breastfeeding can provide diabetes inhibiting effects for over three years.

Common side effects of pregnancy, such as weight gain and insulin resistance, are well-known risk factors for diabetes development.  The risk may be further increased for pregnant women in the presence of obesity, advanced maternal age, multiple births, or in those with a history of gestational diabetes.  Studies such as the Nurses’ Health Study and the 2012 German study by Ziegler et al. have shown a clear correlation between breastfeeding and a reduced risk of diabetes. A study in the South Korean journal, Science Translational Medicine, investigated the extent to which these protective effects occur. 

The purpose of the study was to compare how glucose homeostasis differs between lactating women and women who are not. The non-blinded investigation was a multicenter prospective cohort study that recruited patients from four Korean medical centers between August 1995 and May 1997.  Participants meeting the inclusion criteria were women with a first-time diagnosis of gestational diabetes mellitus (GDM) or gestational impaired glucose tolerance (GIGT). Researchers used parameters determined by the Third International Workshop-Conference on Gestational Diabetes Mellitus for diagnosing GDM and GIGT. Women with persistent diabetes at the initial visit or overt type 2 diabetes mellitus were excluded from the study. Those who attended the first follow-up evaluation at two months postpartum were enrolled in the study. A total of 174 women who independently determined whether to breastfeed or not were analyzed. Of the 174 participants, 85 chose to breastfeed, and 99 did not.

Participants’ metabolic factors were evaluated consistently at predetermined intervals. For example, in the first follow-up evaluation, which occurred at two months postpartum, a face-to-face interview was performed, utilizing a standardized questionnaire to verify past medical history and reproductive history. In addition, patient medical records were used to ascertain specific obstetric histories, including parity and pregestational weight. Evaluations then occurred on an annual basis. A 75-gram oral glucose tolerance test (OGTT) was performed at each evaluation following an overnight fast, and the results were analyzed. The average length of follow-up was 3.6 years postpartum.

Study results revealed improved glucose homeostasis in women who breastfed compared to women who did not. Data were categorized by comparing glucose and insulin levels in the two groups following the 75-gram OGTT at time intervals of 0, 30, 60, 90, and 120 minutes at the initial 2-month follow-up and every annual follow-up after that. Women who did not breastfeed were shown to have consistently higher levels of both glucose and insulin throughout the study when compared to their counterparts. For example, at 120 minutes post-OGTT, the women who did not breastfeed had average glucose levels of 138.229 mg/dL at the initial follow-up and 158.455 mg/dL at their final follow-up. This can be compared to the women who breastfeed, whose glucose levels taken at the same periods were 136.847 mg/dL and 138.953 mg/dL, respectively. Insulin levels also differed between the groups. For example, at 120 minutes post-OGTT, women who did not breastfeed had an average insulin level of 39.165 at their initial evaluation and 52.049 at the final visit. Women who breastfed had average insulin levels of 35.825 at their initial visit and 40.901 at their final visit. Though not all results were statistically significant due to the small sample size, the data is compelling and warrants further research. 

This study had limitations, including a small sample size of 238 participants and a narrow demographic of only South Korean women, so it is not easily generalizable to a large and diverse population such as the United States. Additionally, though this is a recently published study, its participants were recruited over twenty years ago. In this time, population demographics may have changed, making the study less relevant. However, despite the limitations, the study results show compelling evidence of correlating lactation and glucose homeostasis. It has future implications for using mechanisms by which lactation exerts its control over diabetes-related factors such as insulin and glucose in non-breastfeeding patients.

Practice Pearls:

• Glucose and insulin levels are lower in women who are lactating and choose to breastfeed compared to those who do not.
• Breastfeeding can decrease the risk of developing diabetes for at least three years postpartum.
• Diabetes controlling effects of lactation provides a future direction for diabetes prevention research.

Glycemic profiles of the 75-gram OGTT during and after lactation

(Click chart to view full size.)

Moon, Joon Ho, et al. “Lactation Improves Pancreatic  Cell Mass and Function through Serotonin Production.” Science Translational Medicine,

Sameen Khan, USF Pharm.D. Candidate, 2021