Growth during infancy is slightly lower among breastfed infants, but the difference seems to disappear later during childhood. Breastfeeding seems to have a beneficial effect on blood pressure, lipid profile and possible insulin resistance/type-2 diabetes and obesity, but there is no evidence for effects on clinical manifestations of cardiovascular diseases. Potential negative effects include transfer of environmental pollutants and viruses, especially HIV, and the risk of hypernatraemic dehydration during the first weeks after delivery. For the mother, breastfeeding seems to reduce the risk of developing breast cancer.

Schack-Nielsen L, Michaelsen KF.

Københavns Universitet, Det Biovidenskabelige Fakultet for Fødevarer, Veterinaermedicin.

Ugeskr Laeger. 2007 Mar 12;169(11):989-93

There is increasing evidence that breastfeeding has long term beneficial effects on the infant. The most important are improved cognitive development, reduced incidence of immune related diseases (e.g. Type-1 diabetes and inflammatory bowel disease), and childhood cancers. A reduced risk of breast cancer in the mother is another important benefit.

Schack-Nielsen L, Larnkjaer A, Michaelsen KF.
Department of Human Nutrition, The Royal Veterinary and Agric University, Denmark.

Adv Exp Med Biol. 2005;569:16-23.