Doctor's Note
One thing all sufferers should consider is an aspartame-free trial period (see Aspartame-Induced Fibromyalgia).
Why do plant-based diets help with chronic pain conditions? There may be a number of reasons why vegetarians only have about half the odds of being on painkiller drugs (see Say No to Drugs by Saying Yes to More Plants). Potentially inflammatory compounds in animal products include Neu5Gc (The Inflammatory Meat Molecule Neu5Gc), endotoxins (The Exogenous Endotoxin Theory), and animal proteins (Diet & Rheumatoid Arthritis).
On the other hand maybe the potassium in plant foods modulates adrenal function? See my video Potassium and Autoimmune Disease. If it is the Anti-Inflammatory Antioxidants, then that could certainly help explain it. See Antioxidant Power of Plant Foods Versus Animal Foods.
Vegetarian and raw vegan diets appear effective, but what about just mostly vegetarian diets or mostly raw vegan diets? That's the subject of my next NutritionFacts.org video Fibromyalgia vs. Mostly Raw & Mostly Vegetarian Diets.
For some more context, check out my associated blog posts: Plant-Based Diets for Psoriasis, Plant-Based Diets for Fibromyalgia, and How Probiotics Affect Mental Health