The short answer is no, there is no convincing evidence to support the idea that potatoes and tomatoes (or any foods) are bad for rheumatoid arthritis.

The role of diet on arthritis has been a topic of intense debate for years. Researchers have tried to find foods that may be helpful or harmful. So far, no conclusive evidence has been found to say that diet has any role in making rheumatoid arthritis better or worse.

Still, I have many patients who are convinced that diet affects their joint disease. I encourage them to follow whatever diet they feel helps -- as long as it's safe.

In recent years, a popular diet for rheumatoid arthritis is to avoid "nightshade vegetables." These include tomatoes, potatoes, and eggplant. Perhaps this is why your acquaintance was told to avoid them. But again, there is no scientific evidence that avoiding these foods will improve rheumatoid arthritis. In addition, I know of no connection between eating these vegetables and calcium absorption. (Even if there were, there is no obvious connection between calcium absorption and symptoms of rheumatoid arthritis.)

There is much we do not understand about the impact of diet on rheumatoid arthritis or other types of arthritis. I think doctors and patients should keep an open mind about possible connections. I'm hopeful that future research will reveal what role, if any, dietary changes have on rheumatoid arthritis and other forms of arthritis.