Diet may influence the amount and kind of nutrients that enter your body, which can increase the risk of cancer. Some nutrients like antioxidants, certain types of phytochemicals, and other substances can aid in the prevention or treatment of cancer, while others can promote cancer. Fruits and vegetables, for example, include nutrients like antioxidants and phytochemicals that can protect your cells from harm and improve your immune system. However, processed meats, sugary drinks, and animal products in general can cause inflammation and an increase of cancer-promoting hormones like IGF-1.