I love yogurt, not only because it tastes great, but also because it is a very healthy part of my diet. The main ingredient in yogurt is milk, live and active cultures, plus other ingredients such different fruit and flavors, fortified with vitamins. Yogurt is made by adding cultures of certain bacteria to milk. These microorganisms convert the lactose in the milk to lactic acid. The lactic acid gives yogurt its characteristic tart taste and causes the milk to form a soft curd.