Nightshade Foods and Arthritis

The alkaloids in these foods may trigger more intense symptoms

Nightshade foods trigger arthritis — that was a popular theory many years ago. 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 for arthritis pain. The theory persists to this day, but we have learned over the years that avoiding or eliminating nightshade foods helps some people more than others.

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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 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 Nightshades Might 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 slain)
  • 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 nightshade foods 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 the negative impact of nightshade foods for people with arthritis, it has been suggested that some people experience worse symptoms. Some researchers and doctors recommend eliminating nightshade foods 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 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.

An 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 nightshades from their diet in an effort to improve arthritis symptoms. It is fair to assume, though, that if there was a large consensus of success, we would know.

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 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.

It sounds easy to just eliminate certain foods, but identifying which are the offenders is a bit more complicated. You have to be sure you consider the effect of other factors, too, such as activity level, fatigue level, medication changes, and additional stress in your life.

For example, on a given day, more intense symptoms may be related to overdoing activities more than the eggplant Parmesan you ate. If you are able, through elimination, to identify a nightshade food that you suspect is problematic for you, re-introduce it back into your diet later to see if symptoms worsen once again.  

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