Mehmet Cengiz Öz, known professionally as Dr. Oz, is a Turkish-American television personality, cardiothoracic surgeon, Columbia University professor, and author of Circassian origin. In 2003, Oprah Winfrey was the first guest on the Discovery Channel series Second Opinion with Dr. Oz, and, from 2004, Oz was a regular guest on The Oprah Winfrey Show, making more than sixty appearances.