Might be worth taking a look at widipedia entry on alkaline diets.
Sandy
http://en.wikipedia.org/wiki/Alkaline_diet
Proposed mechanism, effects, and evidence basis:
Advocates for alternative uses of an alkaline diet propose that since the normal pH of the blood is slightly alkaline, the goal of diet should be to mirror this by eating a diet that is alkaline producing as well. These advocates propose that diets high in acid producing elements will lead the body in general to become acidic, which can foster disease.[13][11] This proposed mechanism, in which the diet can significantly change the acidity of the blood, goes against "everything we know about the chemistry of the human body" and has been called a "myth" in a statement by the American Institute for Cancer Research.[15] Unlike the pH level in the urine, a selectively alkaline diet has not been shown to elicit a sustained change in blood pH levels, nor to provide the clinical benefits claimed by its proponents. Because of the body's natural regulatory mechanisms, which do not require a special diet to work, eating an alkaline diet can, at most, change the blood pH minimally and transiently.[16][13][11][15]
A similar proposal by those advocating this diet suggests that cancer grows in an acidic environment, and that a proper alkaline diet can change the environment of the body to treat cancer. This proposal ignores the fact that while cancer tissue does grow in acidic environment, it is the cancer that creates the acidity. The rapid growth of cancer cells creates the acidic environment; the acidic environment does not create cancer.[12] The proposal also neglects to recognize that it is "virtually impossible" to create a less acidic environment in the body.[15] "Extreme" dietary plans such as this diet have more risks than benefits for patients with cancer.[12]
Other proposed benefits from eating an alkaline diet are likewise not supported by scientific evidence. Although it has been proposed that this diet will increase "energy" or treat cardiovascular disease, there is no evidence to support these assertions.[13] A version of this diet has also been promoted by Robert O. Young as a method of weight loss in his book The pH Miracle. According to the Academy of Nutrition and Dietetics, portions of his diet such as the emphasis on eating green leafy vegetables and exercise would likely be healthy. However, the "obscure theory" on which his diet is based and the reliance on complicated fasting regimens and nutritional supplements means that this diet "is not a healthy way to lose weight."[14] It has also been proposed that acid causes rheumatoid arthritis and osteoarthritis, and that an alkaline diet can be used to treat these conditions. There is no evidence to support this proposal.[17]
Urinary and/or saliva testing for acidity has been proposed as a way to measure the body's acidity level and therefore the level of risk for diseases.[6] However, there is no correlation between the urinary pH measured in home "test kits" and the acidity of the body.[15]
