In the context of the alarming increase in the early onset of diabetes in women of childbearing age, identifying easily modifiable lifestyle risk factors to prevent diabetes among women is a public health priority. The role of lactation in diabetes risk has not been previously investigated in Latin American populations, where rates of breastfeeding are suboptimal and diabetes incidence is increasing. For example, in Mexico, breastfeeding practices are alarmingly suboptimal. Between 2006 and 2012, the rate of exclusive breastfeeding in infants aged <6 months decreased from 22.3% to 14.4%.
Pregnancy represents a vital window of opportunity to prevent chronic diseases later in life because it allows providers to identify women at high risk of long-term development of hypertension, diabetes and other cardiovascular diseases (women with complicated pregnancy, e.g. hypertensive disorders, gestational diabetes, placental complications, etc.) and the appropriate long-term intervention for lifestyle modification to reset altered maternal metabolism after pregnancy. In addition, the postpartum period is also a window of opportunity to prevent chronic diseases because there are modifiable behaviors that can help to avoid postpartum weight gain, postpartum weight retention and metabolic alterations that can lead to chronic diseases later in life, such as the adoption of healthy dietary patterns, engagement in physical activity and lactation.
Recently, we found in the Mexican Teachers’ Cohort that a mean of six-to-twelve months of lactation per child was associated with lower maternal diabetes incidence in Mexican women (27% lower rate to develop diabetes). Our results are consistent with previous observational studies that have documented the association between lactation and decrease risk of diabetes in different populations. Moreover, we observed that maternal diabetes incidence no longer decreased after a mean of ≥ 12 months of lactation per child. We hypothesize that this could potentially be explained by the fact that after 12 months of age, the frequency and intensity of lactation decrease as breastmilk provides just a third of energy needs in children 12 and 24 months. This suggests that intensity rather than the duration of lactation could have a major role in decreasing the risk of diabetes.
Other research has suggested that lactation could protect against diabetes by promoting postpartum weight loss and less long-term weight gain during childbearing years. However, our analysis indicates that the less long-term weight gain experienced by women who breastfed does not fully explain the association between lactation and diabetes. Therefore, we speculate that other biological mechanisms could explain the protection against diabetes provided by lactation. For example, prolactin effects on preservation and improvement of pancreatic β-cells that persist after weaning, thereby decreasing diabetes risk later in life. Now, with our results, we are one-step closer to understanding the non-linear dose-response association between lactation and diabetes and determining if the intensity of lactation provides greater benefits to maternal health.
In most countries, lactation practices are suboptimal due to biological and sociocultural factors. For example, obese women are more likely to experience delay or failure to lactate, increasing the probability of introducing formula. Therefore, our results are a wakeup call to health providers to provide counselling and support for mothers to initiate and maintain optimal breastfeeding practices because of their potential to prevent diabetes, and to develop interventions, promote policies and scale-up programs at the population level to support, protect and promote lactation. In addition, our results can help to reinforce the importance of breastfeeding particularly in low-income and middle-income countries where breastfeeding practices are suboptimal.