Can sour food cause arthritis? My mother has a pain in her joints every time she eats sour or bitter food. Is this psychological is it really related?

It is more likely to be psychological than mechanistic. Food is broken down in the stomach to its elementary forms. It is unlikely that these amino acids, sugars, and fats will trigger an immune response. Certain foods do cause an immune response. The most common of these is gluten. Gluten is not bitter or sour. Dr. B