From the NY Times OpEd:
I was once a vegan. But well before I became pregnant, I concluded that a vegan pregnancy was irresponsible. You cannot create and nourish a robust baby merely on foods from plants.
Indigenous cuisines offer clues about what humans, naturally omnivorous, need to survive, reproduce and grow: traditional vegetarian diets, as in India, invariably include dairy and eggs for complete protein, essential fats and vitamins. There are no vegan societies for a simple reason: a vegan diet is not adequate in the long run.
Protein deficiency is one danger of a vegan diet for babies. Nutritionists used to speak of proteins as â€œfirst classâ€ (from meat, fish, eggs and milk) and â€œsecond classâ€ (from plants), but today this is considered denigrating to vegetarians.
The fact remains, though, that humans prefer animal proteins and fats to cereals and tubers, because they contain all the essential amino acids needed for life in the right ratio. This is not true of plant proteins, which are inferior in quantity and quality â€” even soy.