I'm strongly committed to breast feeding, but I'm not sure how digestible my breast milk is because lately my baby has been colicky. One book I read said that my breast milk would be more digestible if I cut dairy products out of my diet. I really love dairy, so I'm wondering if there's a way around this. Would it be OK for me to drink lactose-free milk instead of regular milk? What about taking a pill to help me break down the lactose in yogurt and cheese?

I'm glad about your decision to breast feed your baby. Although breast feeding can pose challenges (and joys), it is still true that mother's milk is the perfect food for babies. Milk is, in fact, the basic food for all mammals. Why then do people often experience difficulty tolerating milk?

The difficulties can be caused by two different substances: milk sugar (lactose) and milk protein. Each of these substances produces its own particular problems. Lactose is the sugar in milk. It is the same for any kind of milk--breast, cow, goat, or sheep. A person who is lactose intolerant tends to have gassy symptoms, bloating, and diarrhea after eating dairy foods. These symptoms can be avoided if the person drinks lactose-free milk. Alternatively he or she could take pills such as Lactaid, which enable the intestines to digest lactose without any problem.There are far more people in the world who do not tolerate lactose than people who do. About 80% of all people over age 3 are lactose intolerant. This statistic applies to Native Americans, Asians from the Far East, Southeast Asians, Africans, African-Americans, and Native Australians. It does not apply to Caucasians, however: only 15% of Caucasians in the U.S. are lactose intolerant.

The statistic also does not apply to babies. Infants from all parts of the world do tolerate lactose--otherwise they couldn't digest breast milk well. Their bodies make an enzyme, lactase, which enables them to digest the sugar in milk. As a result, in healthy full-term infants lactose intolerance is extremely rare. It is more common in premature babies, who are sometimes lactose intolerant until they begin to approach their original due dates. At that point, their bodies start making lactase. Newborn lactose intolerance is quite obvious, usually manifesting as discomfort with each feeding. Babies with lactose intolerance are treated with formula that is based on cow's milk but is lactose-free, or else with a soy-based formula. Elemental formulas, which are much more "pre-digested" than usual formulas, also work well for these infants.

Healthy full-term babies can temporarily become lactose intolerant, though, during and after a bout of diarrhea, since diarrhea can cause them to lose the enzyme. Infants regain their tolerance after the diarrhea has ended and their bodies have had time to make more of the enzyme. Eventually, however, in most populations as the babies mature their bodies gradually make less and less lactase. As they grow into toddlerhood, they no longer tolerate milk of any kind.

The other component of milk that can cause people problems is its protein, which comes in two basic forms--casein and whey. The specific proteins differ slightly depending on which mammal the milk is from. The mammal whose milk most often creates digestive difficulties for humans is the cow. Intolerance to cow's milk protein follows the opposite pattern from lactose intolerance, since it is not uncommon in newborns but becomes much less common the older children get. It is estimated that between 2% and 7.5% of healthy infants have significant intolerance to the protein in cow's milk.