Breast milk, while it may contain indigestible substances, is beneficial for the health of infants. At such a young age, they have not been able to establish an substantial immune system. By feeding infants with breast milk, they are able to receive antibodies from their mother, which is helpful in preventing illness which could potentially be fatal in such a young infant. Breast milk is important for the immune health of infants.
Yes, breasts milk is healthy. Even if breast milk contains substances that are not digestible by human infants, this does not mean that breast milk is not healthy. Breast milk was created by God for babies and it is the best nutrition for them even if every substance in them is not digestible.
Of course breast milk is healthy. It has been created by humans to feed our offspring since we were created. There are always going to be things that are produced that aren't digested by the human body. Many that is the purpose if it, to enable our bodies to single out items that can't be digested to prevent accidents.
Breast milk is the preferred method for feeding infants by many in the pediatric community, as well as by many new mothers. However, the quality of the breast milk can depend on the type of diet that the mother eats herself. For example, someone that follows a strict diet, and is careful about what they put into their body will be able to produce milk that is healthier for her baby. Likewise, someone with a poor diet may not have as healthy of breast milk for her baby. In short, breast milk is not nearly as healthy as proponents claim.