You need to worry about cancer because you have a roughly four in 10 chance of coming down with invasive cancer. (Skin cancers like squamous cell and basal cell are quite common, but rarely invasive.)
Dr. David Gorski is a breast cancer surgeon. He’s looked at the scientific literature on the linkage between diet and exercises, and the risk of developing cancer.
Here’s his conclusion from his review at Science-Based Medicine:
“You can reduce your risk of cancer by staying active and exercising, eating a healthy diet with a lot of plant-based foods and minimizing intake of processed meats, limiting alcohol consumption (although I think the WCRF/AICR guidelines go a bit too far in saying that you shouldn’t drink at all if possible), and maintaining a healthy weight. (Of course, if you stay active and eat a healthy diet, maintaining a healthy weight will probably not be a problem.) Conceptually, it’s easy to do. In practice, as I’m discovering, it’s anything but easy.”
Source: Diet and exercise versus cancer: A science-based view « Science-Based Medicine
The Mediterranean diet seems to protect against cancer.
Steve Parker, M.D.
PS: One of the reasons I write diet books is that I want to keep you from getting cancer.
Advanced Mediterranean Diet 