While sugar doesn't necessarily cause cancer, eating sweets, processed carbs, and even high glycemic-index fruits (bananas, pineapple, mango, watermelon, cherries, dried fruit) may encourage cancer cell growth that could be avoided by limiting or eliminating those foods altogether. You can't avoid carbs completely as all your cells need glucose (the byproduct of carbohydrate digestion) for energy. But, because eating sugary carbs causes extra insulin production, insulin-like growth factor-1 production, and a resulting cancer cell growth, it's crucial to choose carbohydrate-rich foods that are high in fiber and low in sugar so that you can fuel your healthy cells and avoid a growth spurt of cancer cells. Please note that avoiding all carbohydrate-containing foods isn't a recommended way to limit cancer cell growth. Since your brain and heart can't live without glucose, your body will make glucose from protein and fats, which is an exhausting chore and lowers your body pH, making your bloodstream and tissues more acidic and immune system less efficient. For more info on sugar and cancer, go here.