That's A. not true as many studies have shown and B. very bad for the environment and for the cow and the calf that were required (to be killed) to get that glass of milk.
Milk is nice. If you can drink and enjoy it, enjoy it. Sounds simple.
A calf is not killed to provide milk. They're weaned from an early age while the mother continues to provide milk for up to 2 years. Milking cows will provide up to 40 liters twice a day.
The calf, like the mother, will eventually be killed for meat, but that is the reality of all meat we eat.
As for drinking milk, the official recommendation in Scandinavia is drinking 0.5L/day.
Since the whole process is highly inefficient. The cow needs more than 100 litres of water a day. It eats a lot, it produces methane. All that, just for your 80 litres of milk a day.
Yes, a cow produces methane, so did the millions of buffaloes roaming the prairies a couple hundred years ago. And so does just about every other herbivore. It’s natural.
What’s not natural is humanity’s insistence on being transported around to just about everywhere, preferably alone, in a vehicle that has room for 6 or more.
The other day I was shopping and came across a cheese that said, manufactured in Denmark, packed in Poland. I’m guessing the cheese produced way more greenhouse gasses on its way to and from Poland than the cow did producing the milk that went into the cheese.
And that’s just the tip of the iceberg.
That being said, at least in the EU, emissions from agriculture is about 40% less than the transport emissions, and still dropping while transport is increasing.
What? My family had a milk cow during my childhood and we never had to kill the cow or her calves to get milk from her. Patently untrue.