Yogurt is made by curdling milk with purified bacteria cultures that cause the milk sugar, or lactose, to turn into lactic acid. The result is a high-calcium, high-protein dairy food. From early on in its history, yogurt has been linked with longevity and has even been used for medicinal purposes.

The exact origin of yogurt is uncertain, but legend has it that the Biblical patriarch Abraham offered yogurt to the angels when they told him of the birth of his son Isaac. Over the years, yogurt has been credited as the reason for the longevity of Abraham, who lived to the advanced age of 175, and some Biblical scholars believe that yogurt is the milk of the phrase "milk and honey."

In the early 1500s, a Turkish doctor was credited with saving the life of the French monarch François I (1494-1547) by prescribing a diet of yogurt...