The book "Gulp: Adventures on the Alimentary Canal" by Mary Roach delves into the complexities of human digestion and the role of different foods. It highlights the common misconception about sugar causing cavities, emphasizing that it's not the sugar itself, but the acidic byproducts produced by bacteria that consume it that lead to dental issues. This clarifies the relationship between sugar, bacteria, and tooth decay.

Moreover, the text discusses how the body naturally counters acidity in the mouth through saliva, which acts to neutralize acids from both sugary and acidic foods. By restoring a balanced pH, saliva plays a crucial role in maintaining oral health, demonstrating how our body's systems work together to mitigate potential damage from our diet.