We have Marco Polo to thank for our knowledge of how Mongolian nomads lived during the thirteenth century. The warriors traveled with horses, which provided almost all of their sustenance.
Mare’s milk was heated, and then the cream was skimmed off just before boiling. The cream was made into butter, and then the rest of the milk was dried.
“Then they stand the milk in the sun and leave it to dry. When they are going on an expedition, they take about ten pounds of this milk; and every morning they take out about half a pound of it and put it in a small leather flask, shaped like a gourd, with as much water as they please. Then, while they ride, the milk in the flask dissolves into a fluid, which they drink. And this is their breakfast.”
While most people with a diet that lacks fruit and vegetables would likely contract scurvy, the high concentration of vitamin C in mare’s milk allowed the nomads to be energetic and healthy.
Source: Food in History, Reay Tannahill