Nightshade Vegetables and Arthritis

Nightshade vegetables are a group of plants that produce alkaloids,  substances that keep insects away.

Some people believe alkaloids cause joint pain and arthritis, but little  research is available to substantiate this, and some research suggests the  opposite.

Tomatoes, potatoes, eggplant, hot peppers, cayenne, paprika and Goji berries  are common nightshade foods. They contain various alkaloids, such as tomatine  (tomatoes), solanine (potatoes), alpha-solanine (eggplant,) solanadine (hot  peppers and spices) and atropine (Goji berries.)

Arthritis is a condition in which inflammation flares up in joints, causing  pain, stiffness and damage to cartilage. Some foods, like nightshade vegetables,  are thought to promote inflammation.

However, a study recently published in The Journal of Nutrition found  markers of inflammation decreased when men were fed white, yellow and purple  potatoes for six weeks, (particularly yellow and purple) which suggests this  nightshade vegetable could actually improve arthritis symptoms.

Another study, part of the Johnston County Osteoarthritis Project in North  Carolina, found people with the highest blood levels of lutein, a substance  found in tomatoes, were 70 percent less likely to have osteoarthritis.

Despite this, some people report nightshades cause joint pain, and it is  possible to have an individual reaction. Test this by omitting them from your  diet for a month and then reintroduce one at a time, observing if they trigger  arthritis symptoms.

Instead of focusing solely on nightshades, consider beefing up specific  nutrients shown to decrease joint pain.

Years of research through the Framingham (Mass.) Osteoarthritis Study, an  offshoot of the Framingham (Mass.) Heart Study, and others find adequate amounts  of vitamin C, vitamin D, calcium and omega-3 fatty acids significantly reduce  pain and inflammation in joints and can slow the progression of arthritic  disease.

Vitamin C is an antioxidant that reduces inflammation and also is vital in  the process of cartilage repair and regeneration. Research finds people who eat  three good sources daily –– citrus fruits, peppers, strawberries, kiwis,  broccoli and the like –– have considerably less joint pain and less damage to  joints over time.

Also essential for cartilage production is vitamin D. Along with adequate  calcium, this important nutrient is needed to maintain strong bones, too, which  is necessary to support joints and reduce wear and damage to cartilage.

Consider having blood levels of vitamin D tested at your next physical. If  normal, maintain adequate levels of vitamin D with at least 600 IUs daily (800  IU after age 51) through foods (milk, fatty fish) or supplement or sunshine in  the summer months.

Aim for three calcium-rich food sources daily (consisting of one cup of  milk, soy milk, yogurt or orange juice fortified with calcium) or make up the  difference with a calcium supplement.

Omega-3 fatty acids found primarily in fish reduce inflammation and may even  prevent arthritis from developing, according to new research.

Switch to canola oil for cooking and choose fish like salmon or tuna often.  Extra omega-3 from a fish oil supplement is beneficial, too, however check with  your doctor to be sure it is right for you.

Joan Endyke is a registered dietitian with a master’s degree in food and  nutrition. Send your questions to her at  This column is not intended to diagnose or treat disease. Check with your doctor  before changing your diet.


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