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. The problem is particularly common in families with strong histories of
eczema,
allergies, or
asthma.
Babies with this intolerance can have discomfort even if they are exclusively breast fed. The difficulty arises when the mother eats or drinks cow's milk protein. The protein passes into her breast milk and from there into the baby's digestive system. Antibodies to this protein have been found in infants who are intolerant, providing evidence of the link between the mother's diet and her baby's digestive troubles.
A study published in the January 1996
Journal of the American Dietetic Association looked carefully at infants' symptoms of fussiness or colic and how they varied with maternal consumption of 15 different foods. Maternal consumption of cow's milk was far more associated with the symptoms of colic than consumption of any other food. The study found that women who drank cow's milk were twice as likely to have infants with colic compared to other breast feeding moms. Another study found that half of women with colicky babies who dropped cow's milk saw marked improvement in their babies' symptoms. A third investigation found that there were higher levels of cow's milk protein in the mothers' milk of colicky infants than in the milk of mothers whose babies were not colicky.
