The methodology you have described indicates that you are altering your digestive tract pH rather than your actual body (blood pH). In this case, it would also seem logical that unless you had prostate or bowel cancer the alkalinity would not reach the cancer and be able to penetrate and help.
Furthermore, while short term and moderated exposure will give you mild gas as a side effect, if you continue long term you face a high chance of stomach ulcers (from destroying the stomach lining), poor nutrition (digestion via the small intestines is aided at lower pH's) and kidney stones.
