Every time you eat eggplant, your knuckles start to throb. This sometimes happens after you eat other healthy foods like tomatoes and peppers.
What gives? These are some of the very foods you are supposed to eat more of to keep your weight down and boost your heart health, right?
Many people with inflammatory types of arthritis such as rheumatoid arthritis (RA) do report a worsening of symptoms such as joint pain and swelling after consuming nightshades. Known in agricultural circles as Solanaceae, nightshades are a botanical family of plants that share certain characteristics. There are around 2,500 species of nightshades (most of which are inedible). Some, namely potatoes, eggplant, tomatoes and pepper, are staples in the American diet.
There are some theories on how nightshades and arthritis symptoms are linked, the main one being that nightshades contain alkaloids – such as the glycoalkaloid solanine – which have pro-inflammatory properties in some individuals.
Loads of anecdotal evidence link nightshades to worsening arthritis symptoms, but there’s little on the scientific side to support this link. To further muddy the waters, a study published in a 2011 issue of the shu showed yellow and purple potatoes (i.e., nightshades) actually lowered blood markers for inflammation in healthy men.
In general, “research does not support the notion that these plant foods should be avoided,” says Lona Sandon, RD, assistant professor at the University of Texas Southwestern Medical Center in Dallas. “In fact, many of the nightshade vegetables are high in the nutrients vitamin C and A that people with arthritis should get more of.”
It doesn’t make sense to give these otherwise healthful foods the boot because you think they may worsen symptoms, agrees Dennis C. Ang, MD, MS, an associate professor of internal medicine-rheumatology and immunology at Wake Forest Baptist Medical Center in Winston-Salem, NC. There is no one-size-fits-all dietary advice for people with RA and other inflammatory forms of the disease, he adds.
“We encourage everyone to eat more fruits and vegetables as they are packed with nutrients, help maintain a normal weight and reduce risk for heart disease, which can be elevated in people with inflammatory arthritis,” he says.
Get to the bottom of what is causing your symptoms by keeping a food diary that tracks how you feel when you eat certain foods – including nightshades. “Don’t eat the offending foods for one week, and then add them back the next week to see if there is any connection,” he says. “If your symptoms improve when you avoid nightshades, then they may be a trigger for you.”
Sandon agrees: “If these foods really seem to increase symptoms, avoid them and replace them with other sources of key nutrients.” A registered dietician can offer suggestions on healthy substitutes.
But remember, she adds, “the difficulty with identifying potential foods that may affect your arthritis symptoms is that symptoms can vary quite a bit due to other factors, such as overdoing physical activity, variations in fatigue levels, having an infection, starting or stopping medications, or hormonal changes.”