Evidence on the long-term effects of breastfeeding : systematic reviews and meta-analyses

"The primary objective of this series of systematic reviews was to assess the effects of breastfeeding on blood pressure, diabetes and related indicators, serum cholesterol, overweight and obesity, and intellectual performance...
Reviewers' conclusions: The available evidence suggests that breastfeeding may have long-term benefits. Subjects who were breastfed experienced lower mean blood pressure and total cholesterol, as well as higher performance in intelligence tests. Furthermore, the prevalence of overweight/obesity and type-2 diabetes was lower among breastfed subjects. All effects were statistically significant, but for some outcomes their magnitude was relatively modest."