Important? Not much anymore. We have other foods to accomplish what milk does due to modern distribution of food throughout the continents resulting in many more choices of extra-regional nutrition sources. .
The nutritional importance of milk lies mainly in it’s comparatively high Calcium bioavailablility and vitamin D content, and the role they play in the development of growing bodies. The bioavalibility of Calcium in cow’s milk is much higher than other foods which makes it an excellent source. Vitamin D insufficiency leads to Rickets, a crippling bone disease which can lead to life-long discomfort and infirmity.
This was a huge problem in past especially after the industrial revolution and especially in the urban young living in temporate climate zones with liimited winter sunlight, high-density industrial areas where the sun was blocked by smog, and where fresh foods—especially green leafy vegetables—were unavailabe to the urban poor. Many of the very first social welfare programs in Europe and America involved providing free milk to urban children.
That being said, I love a cold glass of cow’s milk with my meals and have drank it all my life. It is considered a solid food in many dietary circles and helps filly me up. It is also a very efficient and longer-lasting way to cool off in the heat.
Jews have a much higher lactose intolerance than others, as 75% aren’t able to digest milk sugar. Asians, on the other hand, suffer the least lactose intolerance and come in at around 10%. The rest of us lie somewhere in the middle.
I’ve never met a lactose-intolerant cat but I’ve heard there are a lot of them. This seems new to me and I speculate it may be environmental. This is counter to the advertising and childrens books of the past where the finest thing one could do for kitty was to offer them a fresh bowl of milk or cream. My barn cats get as much goat’s milk as they like every morning as a reward for keeping my stalls rodent-free. They love it.