There are millions of healthy young vegans, depending on their lifestyle and activity. Vegan diet is possible, but only well planned and with the needed complements. Because of this it’s better a vegetarian diet, wich aports these complements with some animal products, instead of artificial products. It’s correct that the human is the only species which have milk of other species in the diet, but this is irrelevant, because its a similar resource of calcium, and vit A, D and complex of B as in the own milk. Try to keep your young child healthy with soy milk, as I have seen in some cases of fanatical vegans, with dire consequences.

But in general I mentioned dairy products, such as cheeses and yogurts, instead of milk, since milk as it is is not well digestible for an adult as it lacks the necessary enzymes to digest it well, only present in children, but this is valid regardless of whether the milk is their own or from a cow, goat or sheep, also a adult cow can’t digest well the own milk. These enzymes are not needed in cheese or other curdled milkproducts. Perhaps humans will evolve in the future with a 5m longer intestine, to allow us to take advantage of all the nutrients from vegetables, but until then there is no option to stay healthy in the long term.

If it is for reasons of sustainability, it is better to use animal products in their proper measure and not abuse them as in our current society. It is better to have 1 top quality steak a week, than a steak from the supermarket every day. Or, switch to insect protein, as is done in many countries, which is certainly the most sustainable source of premium quality protein and nutrients, business as usual. Well basically there is not much difference between a shrimp or a grasshopper.