Simply put, some foods are acidifying when introduced to the body, and others are alkalizing. So what you consume on a daily basis will change the pH levels of your blood, saliva and urine. The pH scale goes from 0-14 (with acidic substances falling below 7 and basic substances falling above 7). Normal levels for body fluid pH hover right in the middle of that range. Foods can either raise or lower your pH level, and this is based on the mineral content of the food – not the actual pH of the food itself. Lemon juice, for example, has a low pH, but has an alkalizing effect on the body when consumed.