There are many theories as to why dogs eat dirt. These theories include missing minerals in their diet, treating intestinal parasites, and perhaps having an upset stomach. A new theory would be to consider the pH of the soil where your dog is eating and how that affects his body.
Soil in dark, shady places where moss grows maybe acidic. An easy test would be to go to the drugstore and buy litmus paper. If a piece of red litmus paper turns blue when dipped in a soil sample mixed with water, then the soil is alkaline. Alkaline is the opposite of acid. If a little bit of the soil mixed with water turns blue litmus paper to red, that means the soil is acidic.
What this means to your dog is he may be trying to regulate the pH of his stomach. If your dog is eating alkaline soil, it may mean his body is too acidic; if your dog is eating acidic soil it suggests his body is too alkaline.
What to do next will be the subject of a future blog post.