Humans by design are predisposed to be lactose intolerant. The only reasons Westerners (mostly) lost this intolerance was due to centuries of eating cheese and having their bodies evolve to adapt to consuming it. Lactose is the number one sugar in breast milk. It’s broken down by an enzyme called lactase which is supposed to disappear in early childhood, right around the time we would naturally wean. Asian cultures are predominantly lactose intolerant because their cultures have had cuisine sans cheese and cow’s milk for millennia (think traditional Japanese, Chinese, and Korean dishes. No cheese. No cow’s milk.) Yet in Western cultures it’s occasionally encouraged to drink milk to make milk. There is no scientific evidence to back this up. You do not need to drink cow’s milk or eat dairy in large quantities to make breast milk. You do need to stay hydrated, eat quality foods, and routinely empty the breast.