There is no question breast milk is the best option for infants, but clinical evidence supporting this claim remains the subject of study. Researchers from The University of Belgrade recently compared the effects of breast milk and infant formula on smooth non-vascular muscles and antioxidant properties of both.

Researchers used spectroscopy to examine antioxidant properties of breast milk and infant formula. Breast milk caused a relaxing effect on smooth muscles and greater antioxidant effects than infant formula. 

Conclusion: Choosing breast milk results in improved antioxidant support, protecting against the development of hydroxyl radicals, and relaxation of the smooth muscles. This could be the result of human superoxide dismutase. Researchers believe breast milk could support gastrointestinal health.

Source: Lugonja N, Spasić SD, Laugier O, Nikolić-Kokić A, Spasojević I, Oreščanin-Dušić Z, Vrvić MM. Differences in direct pharmacologic effects and antioxidative properties of mature breast milk and infant formulas. Nutrition. 2013 Feb;29(2):431-5. doi: 10.1016/j.nut.2012.07.018.

http://www.ncbi.nlm.nih.gov/pubmed/23312765