At the start of the study, 1400 women between the ages of 18 and 30 years for 20 years who had never been pregnant of been diagnosed with metabolic syndrome were recruited. 704 women became pregnant during the course of the study and, of these women, 120 women developed metabolic syndrome. Interestingly, those who developed metabolic syndrome breastfed on average for 2.6 months whereas women who did not develop metabolic syndrome breastfed on average for 7 months. The protective effect of breastfeeding was even stronger for women who had been diagnosed with gestational diabetes (n = 84) compared with women who had not developed gestational diabetes during pregnancy. Although the cause of the protective benefits of breastfeeding is not known, the researchers did find that women who did not develop metabolic syndrome tended to have less abdominal fat and higher levels of HDL (i.e., good) cholesterol. In addition, although insulin levels were not measured, the researchers hypothesize that breastfeeding may lower insulin levels, decreasing the likelihood of developing metabolic syndrome.
Gunderson, E.P., Jacobs, D.R., Chang, V., Lewis, C.E., Feng, J., Quesenberry, C.P., Sidney, S. (2009). Duration of lactation and incidence of the metabolic syndrome in women of reproductive age aaccording to gestation diabetes mellitus status: A 20-year prospective study in CARDIA - The Coronary Artery Risk Development in Young Adults Study. Diabetes. doi:10.2337/db09-1197