The earth and the human body are the same composition. When the earth's terrain is thrown out of balance by pollution, it manifests this imbalance with symptoms like distrubed weather patterns and acid rain. The same thing happens to our body's inner terrain. You already know the symptoms of over-acidification, conditions like heartburn. In this balanced state, oxygen quickly burns our foods for clean, efficient energy.
Alkaline foods are all greens, vegetables and sprouted grains.
The typical diet is inverted. Rather than mostly alkaline, it is highly acid-producing. The acid terrain robs our body of oxygen, and creates a fermentation metabolism. Rather than burn in the presence of oxygen, our foods slowly ferment and rot. Foods like meats, sugars and cereals cause the body to be acidic.