Do higher alkaline diets protect against cancer?

In truth your body regulates its acid/base balance within very tight limits. The pH of your body is very slightly alkaline, and any shifts from the normal pH range are quickly dealt with by your body’s systems. The confusion surrounding this myth may come from the fact that some foods can change the pH of urine, with foods such as meat making it more acidic (lowering the urine pH) and foods such as many fruits and vegetables making urine more alkaline. However, the changing pH of urine is just one of the ways your body uses to keep overall blood pH in a very narrow range. 

Well designed studies on alkaline diets in people are lacking and there is no good evidence that they can be used to prevent or treat diseases such as cancer. While basing your diet on vegetables and fruit (said to be alkaline producing), may seem harmless, avoiding many of the foods said to cause acidity in the body could result in you missing out on important nutrients.