Higher in protein than cow's milk, this milky, iron-rich liquid is a nondairy product made by pressing ground, cooked soybeans. Soy milk is cholesterol-free and low in calcium, fat and sodium. It makes an excellent milk substitute for anyone with a milk allergy; such milk substitutes are often fortified with calcium. There are also soy-based formulas for infants with milk allergies. Soy milk has a tendency to curdle when mixed with acidic ingredients such as lemon juice and wine; it's intentionally curdled in the making of tofu.