Are Nightshade Vegetables Bad for Arthritis?

Woman holding tomatoes in hands.
Dougal Waters/Digital Vision/Getty Images

Many years ago, when I was first diagnosed with arthritis, a popular theory was circulating -- nightshade vegetables trigger arthritis. The implication was that if people with arthritis avoided nightshade foods or eliminated them from their diet, pain and other symptoms of arthritis would diminish. It was touted as a real solution to arthritis pain. The theory persists to this day, but we have learned over the years that avoiding or eliminating nightshade vegetables helps some more than others.

What Are Nightshades?

"Nightshades" refer to more than 2,800 species of plants that are grown in the shade of night. The plants belong to the scientific order of Polemoniales and the Solanaceae family of plants. The nightshades include numerous vegetables: potatoes, tomatoes, sweet peppers, hot peppers, eggplant, tomatillos, tamarillos, pepitos, pimentos, paprika, and cayenne peppers. Hot sauces made from the hot peppers are considered nightshades. Also, ground cherries, garden huckleberry, naranjilla, and even tobacco are considered nightshades. (Note: sweet potatoes, yams, and black pepper are not included among the nightshades.)

Why Might Nightshade Vegetables Trigger Arthritis?

The offending part of nightshades that may cause problems for some people with arthritis is thought to be the alkaloids. There are four types of alkaloids in nightshade plants:

  • steroid alkaloids (the most noteworthy being solanine)
  • tropane alkaloids
  • pyrrolizidine alkaloids
  • indole alkaloids

Steroid alkaloids are the alkaloids most commonly found in nightshade foods. The other types of alkaloids have been more researched because they have drug-like properties. Alkaloids apparently interfere with calcium metabolism. One theory suggests that nightshades remove calcium from bone and deposit it in soft tissue.

Another theory is that nightshades are pro-inflammatory substances, provoking immune and inflammatory reactions in the body.

The leaves of all nightshade plants contain nicotine, but in much lower amounts than in tobacco. Some experts have suggested that the amount of nicotine in nightshades is inconsequential -- far too little to have a negative impact that would contribute to arthritis. It is fair to conclude that with these competing theories, it is not fully understood how nightshades affect arthritis, if at all. Most information has come from surveys and patient testimonials, not human scientific studies.

How to Know if You Are Sensitive to Nightshades

While there has been no research that confirms nightshades negatively affect people with arthritis, it has been suggested that some people with arthritis experience worse symptoms after consuming nightshade vegetables. Some researchers and doctors recommend eliminating nightshades for 2 or 3 weeks to see if your arthritis symptoms improve. Even if your symptoms do improve, until researchers can prove a connection, skeptics will choose to believe that your improvement is due to a placebo type effect, whereby the elimination of nightshades worked simply because you expected it to work.

Also, if symptoms improve for you, it could be indicative of a food allergy.

Whether or not you choose to eliminate nightshades is completely up to you. The elimination trial won't hurt you and just may help you. But, keep your expectations realistic. It's impossible to know precisely how many people have tried eliminating nightshade vegetables from their diet to improve arthritis symptoms. If there was a large consensus of success, we would know.


What Are Nightshades and in Which Foods Are They Found? The World's Healthiest Foods. The George Mateljan Foundation. Accessed 3/17/2015

Nightshade Vegetables May Cause Adverse Reactions in Some People. Natural News. Deanna Dean. 1/20/2010.

Continue Reading