Cancer is divided into stages. The first stage is initiation. This is where cancer starts, with genes which may become capable of producing cancer cells as they divide. Then the promotion stage may take years in order for the cancer to grow enough to be detected. Nutrition is important here as what we eat can promote the cancer cells to grow. In particular, animal protein is the food substance that Dr. Cambell's research discovered best turned on the cancer ability to grow.
Dr. T. Colin Campbell, author of The China Study, briefly explains in this short Forks Over Knives clip that animal protein promotes cancer by "turning on" cancer genes and acting as "fertilizer," which fuels cancer progression. A detailed explanation of this process can be seen in the Forks Over Knives documentary.
This is a short, but very well stated video from one of the leading experts in the field.
For more information see: