Research on breastfeeding and type 2 diabetes suggests prolonged lactation may reduce the risk for women with a history of gestational diabetes.
Women undergo many metabolic changes during pregnancy to properly nurture the growing fetus and to prepare their body for birth and lactation. To compensate for the deterioration of insulin sensitivity associated with pregnancy, most healthy women develop an increase in insulin secretion. Gestational diabetes mellitus (GDM) develops when this compensatory mechanism is insufficient, and glucose homeostasis is lost. GDM puts women at a 7-fold higher risk of T2D compared to women with normoglycemic pregnancies. Large-scale prospective data and short-term investigations have associated early postpartum breastfeeding with the favorable recovery of insulin sensitivity. However, data are lacking on lactation duration and biomarkers of glucose metabolism long-term.
The secondary analysis of a cohort study by Glover et al. looked at breastfeeding practices of women with and without GDM at six to ten weeks postpartum to evaluate glucose tolerance. The goal was to show mechanistic evidence that breastfeeding improves metabolic outcomes postpartum. Two subject categories, exclusively breastfeeding or not exclusively breastfeeding, were analyzed with regression models for continuous outcomes. Exclusive breastfeeding was associated with a decrease in fasting glucose by 4 mg/dL (p = 0.004) after adjustment for GDM status, maternal BMI, and ethnicity. Although this seems like a small difference, it shows a positive relationship between breastfeeding and reductions in fasting glucose, which supports a healthier metabolic recovery while breastfeeding. A significant limitation is that the “not exclusively breastfeeding” group was also composed of women who were feeding both formula and breastfeeding, which may have convoluted outcomes data.
A prospective cohort study by Ley et al. focused primarily on women with GDM. The aim was to determine the associations of lifetime lactation duration with T2D risk and biomarkers of glucose metabolism later in life. The Nurses’ Health Study (NHS) II is an on-going prospective cohort of registered nurses from the United States. From this cohort, 4,372 women with a history of gestational diabetes were included in the Diabetes & Women’s Health Study. Women with cancer, cardiovascular disease, or multiple-birth pregnancy before the GDM pregnancy were excluded. The study used questionnaires to obtain information on lactation history and other risk factors. Multivariate time-dependent Cox proportional hazards models were used to estimate hazard ratio and 95% CI for T2D risk. Finally, linear models were used to assess associations with glucose metabolism biomarkers.
After adjustment for age at first birth, ethnicity, family history of diabetes, parity, smoking, physical activity, diet quality, and pre-pregnancy BMI, the analysis showed HR 1.05 [95% CI 0.83-1.34] for up to 6 months, 0.91 [0.72-1.16] for 6-12 months, 0.84 [0.67-1.06] for 12-24 months and 0.73 [0.57-0.93] for >24 months compared to 0 months. Therefore, longer lifetime lactation duration was associated with a lower risk of T2D (P for trend = 0.004). Also, longer lactation duration was statistically significantly associated with lower concentrations of HbA1c, fasting insulin, and C-peptides in women free of T2D assessed at a median age of 58.2 years.
There is a strong potential protective effect of prolonged lactation duration in women with a history of GDM . Additionally, the assessment of fasting insulin and C-peptide biomarker in this study is valuable as there is a consensus that these values are a measure of insulin resistance in those without diabetes. Longer lactation duration was associated with both a decreased risk of developing T2D and more favorable biomarkers later in life in women with a history of GDM. The significant limitations are that other healthful behaviors might have confounded benefits, and precise measurements of pregnancy and early postpartum clinical parameters were lacking. Overall, breastfeeding improves metabolic recovery postpartum as well as decreases the risk of T2D development.
- The longer lifetime duration of lactation is associated with a lower risk of developing T2D in women with a history of GDM.
- Middle-aged women with a history of longer lactation duration and who are free of T2D have lower concentrations of glucose metabolism biomarkers (e.g., HbA1c, fasting insulin, and C-peptides).
- Women should always maintain a healthy weight, diet, and exercise routine during and after pregnancy to prevent T2D.
Breastfeeding and type 2 diabetes references:
Ley, Sylvia H et al. “Lactation Duration and Long-term Risk for Incident T2D in Women With a History of Gestational Diabetes Mellitus.” Diabetes care vol. 43,4 (2020): 793-798. doi:10.2337/dc19-2237
Shub, Alexis et al. “The effect of breastfeeding on postpartum glucose tolerance and lipid profiles in women with gestational diabetes mellitus.” International breastfeeding journalvol. 14 46. 4 Nov. 2019, doi:10.1186/s13006-019-0238-5
Stephanie Anderson, PharmD Candidate 2021, Skaggs School of Pharmacy and Pharmaceutical Sciences