It is your body's engine, playing a critical part in your overall health and well-being. And like any engine, your heart can require an occasional tune-up. But what happens when it fails? Artificial hearts and organ transplants are the subjects of this episode of Second Opinion.

Cervical cancer is caused by several types of a virus called human papillomaviruses (HPV). The virus spreads through sexual contact. Most women's bodies are able to fight HPV infection. But sometimes the virus leads to cancer. You are at higher risk if you smoke, have many children, use birth control pills for a long time, or have HIV infection.

What if you could prevent cancer and heart disease by simply buying a few items off the grocery shelf? Sound crazy? Well, apparently many Americans don't think so. More than 40% of us take vitamins and other supplements, driving a $30 billion a year business that shows no sign of slowing down. But how safe is it to play your own doctor? Practitioners of both conventional and integrative medicine debate the pros and cons of nutritional supplements on this episode of Second Opinion.