Citric Acid. Sounds like it comes from citrus fruit, right? While it does occur naturally in citrus fruit, there is a synthetic form of citric acid is known as MCA (manufactured citric acid).
Manufactured Citric Acid is a preservative found in many processed foods, canned products, beverages, and supplements. MCA is not the same as the naturally occurring acid in fruit. It is derived from a fungus called Aspergilus niger (black mold).
Medical Medium says this form of Citric Acid irritates the stomach lining and the intestinal tract, creating a lot of inflammation and discomfort if you're sensitive to it. I have also heard Medical Medium mention that it can trigger anxiety.
The next time you are at the grocery store, look out for citric acid on the label - it is most likely a synthetic form, and it's best to avoid it.