The alkaline diet is based on the principle that food, when it is metabolised in the cells of the body, leaves what is known as an "ash", which is either acidic or alkaline. The theory proposes that an alkaline ash is conducive to good health and an acidic ash is conducive to bad health. The idea is that the diet should be 80% alkaline foods and 20% acidic foods because it takes four parts alkaline to neutralise one part acid; 80% is four times 20%.
I first started to experiment with the alkaline diet several years ago and the results were startling. After six months, an old allergic reaction to certain grasses cleared up; whereas previously I would block up in the sinuses if I lay down on grass, suddenly, after six months, I found that I could lay down on grass without blocking up.
After seven months, my incipient arthritis was starting to ease up; where previously I had been getting pain in various places, after seven months these places felt stiff but not painful. After twelve months, even the stiffness was gone. Sinus trouble caused by allergic reactions to house dust and house mites also disappeared completely. I also found that my neck felt a lot looser than before, and did not make bloodcurdling cracks and crunches when I shook my head from side to side. In other words, results were remarkable (I should admit that I cheated to an extent by using various supplements, but more about that elsewhere).
Alkaline foods are generally vegetables, citrus fruits, soy and tap water (spring water is mildly acidic).
Acidic foods are more numerous and often include nourishing foods like grain, meats and fish, which is what makes it difficult to have an alkaline diet. Rubbishy "foods" like sugar are predictably acidic.
For more detailed information on the alkaline diet, see my website on the subject: