Breastfeeding protects against type 1 diabetes mellitus: a case-sibling study

Some epidemiological studies have shown a protective effect of breastfeeding against type 1 diabetes mellitus (T1DM), whereas others have found opposite results. The role of early exposure to cow's milk protein and shorter duration of breastfeeding are still controversial. This study aimed to compare the frequency and duration of breastfeeding among siblings with and without T1DM.

A case-control study was conducted at the Prof. Fernando Figueira Institute of Integral Medicine, Recife, PE, Brazil, between June 2009 and August 2010. The case patients were children with T1DM, and the controls were their unaffected sibling. The World Health Organization criteria for T1DM were used. All T1DM cases had the diagnostic criteria confirmed by checking their medical records. Data on infant feeding during the first year of life, prenatal care, gestational age, delivery, birth weight, and immunization status were collected through information provided by the mothers.

In total, 123 children with diabetes mellitus type 1 and their respective siblings were studied. There was no difference in breastfeeding rates among the two groups, but patients with diabetes had a shorter duration of breastfeeding (3.3 vs. 4.6 months, p < 0.001). The diabetic group was exposed earlier to cow's milk. After controlling for other associated variables it was shown that a longer duration of breastfeeding was associated with a protective effect against diabetes.

Our data support the proposal that a shorter breastfeeding interval may contribute to T1DM in Brazilian children.