Mothers Who Don't Breastfeed Have Double Risk of Diabetes

Eleanor Bimla Schwarz, MD, of the University of Pittsburgh, PA, and colleagues also reported that, women who had never breastfed were almost twice as likely to develop the disease as women who had never had children. 

"These findings highlight the importance to maternal health of consistent lactation after each birth and add to a growing body of literature that indicates that women who give birth but do not breastfeed face an increased risk of developing diabetes mellitus and subsequent cardiovascular disease," they wrote.  

Recent studies have shown that lactation is associated with improvements in maternal glucose metabolism, and that longer duration of breastfeeding may reduce the risk of diabetes. These studies, however, have had limited data on the duration and exclusivity of breastfeeding and its effects on disease development.

So the researchers looked at a cohort of women ages 40 to 78 from California who participated in the Reproductive Risk Factors for Incontinence Study at Kaiser (RRISK) between 2003 and 2008. There were a total of 2,233 women, 1,828 of whom were mothers. It was a multiethnic cohort, with 20% of participants being black, 18% Asian, and 18% Hispanic.

Obesity was common, with 68% of patients having a body mass index (BMI) of 25 or greater. The majority of mothers (62%) had breastfed one of their children for at least one month. Those who breastfed were more likely to be white, in a committed relationship, and employed full-time.

The researchers found that after adjustment, the risk of Type 2 diabetes among those who consistently breastfed all of their children was similar to that of women who had never given birth. In contrast, mothers who had never breastfed were more likely to have developed Type 2 diabetes than nulliparous women (OR 1.93, 95% CI 1.14 to 3.27).

Mothers who supplemented feedings were more likely to get the disease than those who exclusively breastfed for one or more months (OR 1.38, 95% CI 1.06 to 1.81).

The reasons for the relationship aren't clear, the researchers said, but they noted that lactation suppresses gonadotropin levels and has been associated with lower and slower responses to growth hormone. Breast-feeding may also decrease visceral adiposity (which women gain in pregnancy) and might induce long-term changes in the hypothalmic-pituitary axis.

The study may be limited by recall bias or reporting bias, but the researchers still concluded that their findings show even just one month of breastfeeding may be enough to prevent diabetes.

"Mothers should be encouraged to exclusively breastfeed all of their infants for at least one month," they wrote. They also noted that future studies are needed to determine whether mothers who lactate for shorter periods accrue similar benefits.

• Explain to interested patients that women who exclusively breastfed all of their infants for at least one month had a lower risk of developing Type 2 diabetes in a population study.
  
  
• Note that self-report could have confounded the results, and that the study could not establish causality.

Bimla Schwarz E, et al "Lactation and maternal risk of Type 2 diabetes: A population-based study" Am J Med 2010; DOI: 10.1016/j.amjmed.2010.03.016.