What is pH and how is it measured?
For chemists and scientists, pH is a scale between 1-14 on how acidic (pH < 7) or alkaline (pH > 7) something is. For people concerned about an acidic diet and acid erosion, the most important thing to know is this: the lower the pH number, the more acidic a food or drink is, and the more frequently it is consumed, the more harmful it may be to your tooth enamel.
For example, distilled water has a neutral pH of 7, while tomato juice might have a pH of 4 and lemon juice might have a pH of 2 - making the lemon juice the most acidic of the three.
Knowing the pH value of the foods we eat and the beverages we drink helps us have a clearer picture of how acidic our diet really is. And knowing the acidity of our diet is an important step in making sure we protect our tooth enamel from acid erosion. The rule of thumb is the lower the pH, the higher the acidity and therefore the higher the risk it may cause acid erosion.