In fact, the latest credible research suggests that nightshade vegetables might actually help reduce arthritis symptoms. Earlier this year, a study in the Journal of Nutrition showed that both yellow and purple potatoes reduced blood markers for inflammation in healthy men. Other research, including the Johnston County Osteoarthritis Project in North Carolina, published in the journal Public Health Nutrition, found that people with the highest serum levels of an antioxidant in tomatoes called lutein were 70 percent less likely to have OA.

THE BOTTOM LINE: People with arthritis may actually benefit from nightshades.

The myth: A low-acid diet lessens arthritis pain.

THE SCIENCE: No formal research has been done on this because what you eat won’t really affect the blood’s optimal pH of 7.4, says Dr. Rosenberg. Any food, whether low or high in acid, is bathed in hydrochloric acid when it reaches the stomach. Other compounds then act on the food particles to reach the proper pH before nutrients are absorbed by the bloodstream. It happens automatically; you don’t have to aid the process with your food choices.

THE BOTTOM LINE: Just like drinking acidic vinegar won’t ratchet down stiffness and pain, neither will avoiding acidic foods.

The myth: A raw food diet relieves symptoms.

THE SCIENCE: In the late 1990s, Finnish scientists reporting in the British Journal of Rheumatology put a group of people with RA on either a traditional diet or a raw vegan diet supplemented with beverages rich inlactobacilli – bacteria considered good for the gut and possibly the immune system. Those on the raw diet reported more relief of symptoms. Furthermore, when they returned to a diet that included cooked foods, including meat, their symptoms were aggravated.

But the positive effects of raw food were not discernible in what the researchers called objective measures of disease activity, including duration of morning stiffness, pain at rest and pain on movement. And half of the raw food eaters experienced adverse effects like nausea and diarrhea during the diet and stopped the experiment prematurely.

THE BOTTOM LINE: Eating plenty of uncooked fruits and vegetables is a good idea, as long as you ramp up slowly so the extra fiber won’t cause stomach discomfort. But it’s not clear that such a dietary change itself will bring arthritis relief, especially since the diet here was supplemented with a specially made beverage containing specific bacteria.