It would have been interesting if the author had further investigated how other cultures deal with child nutrition, for instance Japan where the consumption of dairy food is not the norm. They don't have child malnutrition problems, but also don't force cow's milk down their children at every chance.
Adults can be B12 and iron deficient through other problems than their dietary intake - perhaps the same applies to children. We certainly are not going to find out from this flit across the surface of the subject, which raises many more questions that it attempts to answer.