Why do breast-fed babies poop more than bottle-fed babies?

Breast-fed babies tend to make more poops than formula-fed ones: two to five a day, maybe even after every feeding, compared to one or two a day for formula-fed infants. Why? Breast milk contains immunoglobulins, substances produced by the body's immune system, which also work as natural laxatives. This is especially helpful for clearing meconium, while also contributing to frequent pooping and a lack of constipation in nursing babies. These poops tend to be less smelly than poops from kids drinking formula; nature's way of saying thank you, perhaps, for using breast milk. But breast-fed babies may vary their patterns; what you eat and drink gets passed along in the milk, and that may or may not agree with your child.