According to the theory of foods and how they affect the body's acid/alkaline balance, animal protein creates a more acid environment. It's calcium that would offset that acid.

Ph diets are a bit controversial and there are differing opinions on what has exactly is acid-forming and alkaline forming.

If people don't have enough alkaline foods, it may cause calcium to be excreted from the bones to offset the acidity. It's a recognised possible risk in osteoporosis.

More here: https://www.pccmarkets.com/sound-consumer/2009-10/sc0910-acid-alkaline/