Tomatoes, peppers and goji berries are touted for their health benefits. But these nutrition-packed foods have a dark side for those who experience intolerance or allergic reaction. Plants from the nightshade family may cause, or contribute, to arthritic symptoms.

Nightshade plants produce drug-like chemicals, called alkaloids. These alkaloids - nicotine, atropine, capsaicin, solanine, and tomatine - build up in the body’s tissues and may produce pain and inflammation in the joints and muscles. Nightshades were originally used as ornamental plants because of their toxic nature.

One 20-year study, of 1,400 volunteers, found nightshade to be a causative factor in arthritis in sensitive people. In another study, 72.7 percent of the 763 participants reported a marked lessening of arthritis symptoms when they strictly eliminated nightshade foods and/or tobacco.

Norman Childers, a horticulturalist, was one of the first to make the connection between nightshade plants and pain in people after he studied cattle that had developed arthritis from grazing on nightshade plants.

Nightshades are plants from the Solanaceae family, including tobacco, potatoes, eggplant, hot and sweet peppers, tomatillos and gooseberries. Spices and condiments made from nightshades include cayenne, chili powder, curry, paprika, ketchup and Tabasco. All nightshade foods contain nicotine in some form.

Allergic reaction to nightshade is easier to diagnose than intolerance. Allergic individuals get immediate feedback in the form of nausea, diarrhea, dizziness, inflammation, migraines, pain or weakness after ingesting a particular nightshade food.

The problem with intolerance is that symptoms are delayed, sometimes by several days. That makes it difficult to see a causative relationship between their arthritic symptoms and eating nightshade foods.

The best way to diagnose intolerance is to follow a “no nightshades” diet for at least one month. That means you avoid eating all nightshade vegetables and spices. You also abstain from tobacco use as well.

To be effective, the diet must be followed rigidly. Unfortunately, nightshade starch and spices are used in some processed foods that you might not suspect. Read food labels carefully.

Watch for terms like, “flavors, natural flavors, natural flavoring, spices and food starch” as these may contain nightshade. Processed foods, with nightshade starch or spices as ingredients, include: breads, baked goods, crackers, breading, stuffing, sausage, cold cuts, seafood, mock seafood, gravy, sauces, meat sauce, fish sauce, condiments, salad dressings, baked beans, nuts, seasonings and cola drinks.