Milk is just another food. 

https://www.pbs.org/newshour/economy/got-milk-lactose-tolerance-influenced-economic-development

&gt; Milk’s role in influencing economic development is threefold. First, milk allowed farmers to obtain a greater quantity of calories from fixed resources — the stock of domesticated animals and the land needed to sustain these animals. In a sense, dairying represents a technological innovation, in which available resources — that is, land and domestic animals — were used in a novel way to increase output.

&gt; Second, the composition of milk, which includes fats, proteins and other micronutrients not easily attainable in staple crops improved the average quality of a farmer’s diet. This nutritional improvement likely lessened the impacts of disease and led to more productive farmers.