This experience I'm going to relate to you happened a few years ago when I worked as a newborn intensive care nurse. We had a baby that was born premature, not too early, but was very underweight for it's age. The mother was unwed, vegan, and in general not very responsible, or prepared for the task at hand. Babies generally aren't strong enough to nurse at that age and weight but we will give them pumped mothers milk that is stored from that mother. (mother's milk is not shared, contrary to popular opinion.) Anyway we had to stop giving this baby the mother's milk because she wasn't eating enough fats or protien, even with added calories to the milk(very common practice for premature, and underweight babies until they are close to 5 or 6 lbs and gaining well), the baby was not gaining weight and was actually loosing weight. We kept telling the mother she needed to eat more than carrots (the milk was a bright orange.) or the baby would not get better, and we would have to give it formula designed for premies. Nothing worked, and we had to do it. Her milk was not even good enough to provide the other benefits the baby needed because of the poor nutritional factor in the milk.
Sad, sad case, because that is what is prefered to give babies. Most of the time, mother bodies make exactly what the baby needs at that time, meaning it changes as the baby grows and develops. Studies done at BYU showed that the Mother milk of a premie is much different in composition from that of a full term healthy baby, and the MM of a year old child is pretty much water, with very little nutrient value because most children at that age get there nutrients from other sources.
So perhaps the brain damage from the babies of Vegans is not just from b-12 deficiency but also damage from not enough fat, calories and protien?
Tanya