According to various articles, including the Journal of Dairy Science, milk contains Molybdenum.
It makes sense, since Molybdenum is excreted in breast milk, and Molybdenum is a common trace element in alfalfa hays. In fact, quite a number of studies have been done due to Molybdenum toxicity in cows. Appearantly, cows need Copper supplements to help regulate the Molybdenum in their diet.
Also, Molybdenum can be found in potatoes. The quantity depends on the amount found in the soil (as does any green leafy like cabbage), and potatoes absorb much less than green leafies. However, when you eat 8 pounds a day, I’m sure it adds up. Between that and milk, I can’t see where the deficiency is in the diet.
Linky to the article
Edited for readability