Nightshade Foods and Arthritis

Many people believe that nightshade foods may contribute to arthritis. In fact, sometimes people with arthritis avoid nightshade foods or eliminate them from their diet in the hopes that pain and other symptoms of arthritis may diminish. There is no scientific evidence to back this claim, and a few small animal studies suggest that nightshade plants may counteract the inflammation that's characteristic of arthritis.

The Foods That Classify as 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 hot peppers are considered nightshades.

Also, ground cherries, garden huckleberry, naranjilla, and even tobacco are considered nightshades. Note that sweet potatoes, yams, and black pepper are not included among the nightshades.

Nightshades and Arthritis

The component of nightshades implicated in arthritis is thought to be alkaloids.

There are four types of alkaloids in nightshade plants:

• Steroid alkaloids
• Tropane alkaloids
• Pyrrolizidine alkaloids
• Indole alkaloids

There is not a consistent explanation for why nightshades or alkaloids have been implicated in arthritis.

One theory suggests that nightshades remove calcium from bone and deposit it in soft tissue. Another theory is that nightshades may have 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. 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 nightshade foods might or might not affect arthritis, if at all. Most information has come from surveys and patient testimonials, not human scientific studies. In fact, the Cleveland Clinic has published an interview with an expert rheumatologist stating that the link is a myth.

How to Know if You Are Sensitive to Nightshades

While there has been no research confirming any impact of nightshade foods on arthritis, it is important that you avoid any food that worsens your symptoms, whether they are nightshades or not.

If your symptoms improve after eliminating a specific food from your diet and worsen when you start eating the food again, it could be indicative of a food allergy or intolerance. Be sure to talk to your doctor about such a pattern if you notice it.

A Word From Verywell

Whether or not you choose to eliminate nightshade foods is completely up to you. If you choose to try, do it methodically by keeping a food and arthritis symptom diary. The diary will help you track what you eat, what you eliminated from your diet, and when, and to notice any trends in your pain level or other symptoms.

If you decide to eliminate any food from your diet due to your arthritis, be sure to talk to your doctor or to a nutritionist so you can ensure that you are getting enough macronutrients, vitamins, and minerals from the food you eat.