You can't tell how acidic a food is by looking at it. It's not on the nutrition label either. But you can research a food's pH, which is a score of its acid content. The lower the pH number, the higher the acid -- lemon juice has a pH of 2.0. If you aim for foods with a pH of 5 or above, you may have fewer symptoms. You can find the pH level of foods on some government sites and in low-acid diet cookbooks.