Food. For preference, in as close to its natural state as possible.
Vegetables. Fruits. Meats. Water. Cereals are 'filler' foods with low calorie content (except vitamin-pill and sugar bomb products like Total, and Wheaties) which in most people's diets displace healthier, more nutrient-dense foods.
There is no single 'must eat' food for milk production. Cows eat milk and grass. Rats eat garbage... as do goats. And pigs. Cats eat birds and mice. Dogs eat rotting meat and dung... If you see something here you'd like to eat to 'make milk' feel free to select it.
Otherwise, eat food. Healthy, wholesome, real food. And drink water.
at 4:35 AM on Jan. 2, 2011