Do Tomatoes Really Cause Inflammation and Joint Pain?

Nightshade vegetables like tomatoes top some lists of arthritis foods to avoid. But what's really behind that claim — and is it legit?

Truth is, there's little evidence to support the idea that tomatoes are bad for arthritis, including autoimmune forms like rheumatoid arthritis (RA). Same goes for other veggies in the nightshade family, most experts say.

Read on to learn about the dietary changes that might help you better manage your RA. Plus, how to decide if it's worth temporarily cutting out tomatoes or other nightshades for the sake of your joints.

Tomatoes are members of the nightshade family, a group of some 2,500 plants that also includes potatoes and eggplant. All nightshades contain solanine, an insect-repelling compound that, in large quantities, is poisonous to humans, according to the Arthritis Foundation.

Tomatoes, of course, don't have nearly enough solanine to be toxic to people. (If they did, we'd be hearing about cases of killer pizzas and marinara sauces all the time.)

But can the solanine in tomatoes worsen your rheumatoid arthritis?

Some older studies on mice have shown that solanine can inflame and damage the intestinal lining of rodents, the Arthritis Foundation says. A more recent review published July 2023 in ‌Digestive Diseases and Sciences‌ also suggested nightshades could trigger gut inflammation that may worsen symptoms of inflammatory bowel disease.

That said, there's no evidence to show that eating nightshades like tomatoes will worsen symptoms of rheumatoid arthritis, the Arthritis Foundation says. "Most people tolerate nightshades just fine," says EA Stewart, RDN, a San Diego-based dietitian specializing in nutrition for autoimmune diseases.

What's more, nightshade vegetables are known for being nutrition powerhouses. Tomatoes — including cherry tomatoes — are packed with antioxidants including lycopene, folate, vitamin K and vitamin C. These nutrients are all known to ‌reduce‌ inflammation in the body, notes Johns Hopkins Medicine.

That's led the majority of experts to conclude that, for most people with RA, the benefits of eating tomatoes and other nightshades likely outweigh any potential downsides.

"With this in mind, I will work with my patients with RA who want to try a short trial of removing nightshade vegetables from their diet. But it's never my first recommendation," Stewart says.

If you've tried making other dietary changes and are following your doctor's prescribed RA treatment plan and still don't feel like your joint symptoms are adequately controlled, there's no harm in seeing whether a nightshade-free diet helps you.

Stewart recommends following an elimination diet and cutting out the veggies for between two and four weeks (without making any other dietary changes). If your symptoms haven't improved by then, chances are nightshades aren't the issue, and you can start eating them freely again.

If you notice avoiding nightshades helps you feel better, try reintroducing each nightshade vegetable one at a time, waiting three days for each vegetable, to see if a particular one seems to trigger your symptoms. Once you pinpoint the specific culprit, you can continue steering clear without avoiding other foods unnecessarily, recommends the Arthritis Foundation.

There's no cure for rheumatoid arthritis, and dietary changes won't completely eliminate a person's symptoms.

Starting treatment early with disease-modifying antirheumatic drugs (DMARDs) like methotrexate is the most effective option for managing symptoms long-term and keeping RA from getting worse, per the Mayo Clinic.

That said, a healthy diet can support your prescribed treatment and help you feel your best. Eating foods high in the following can increase inflammation and in turn worsen joint pain, says the Arthritis Foundation:

• Saturated fat
• Refined carbohydrates
• Added sugar
• Trans fats
• Salt and sodium

On the other hand? Anti-inflammatory foods like fruits and vegetables, whole grains, lean proteins and healthy fats have been shown to reduce pain and improve function in people with rheumatoid arthritis, found a May 2018 ‌Rheumatology International‌ review.

Stewart encourages a Mediterranean diet for clients with RA who are looking to improve their symptoms with food.

"It features lots of colorful produce, extra-virgin olive oil, omega-3 rich fish such as salmon, mackerel, and sardines, whole grains, nuts and seeds, herbs and spices, and lean proteins including beans and lentils," she says.

A Mediterranean-style diet that's low in unhealthy fats, refined carbs and added sugars might also make it easier to lose weight. And dropping excess body fat can also play a role in reducing inflammation and easing joint pain, the Mayo Clinic notes.

Tomatoes are unlikely to trigger or worsen RA symptoms for most people. But if you're allergic to grass pollen, you might also find that eating raw tomatoes causes allergy-like symptoms in your mouth and throat, notes the American College of Allergy, Asthma, & Immunology (ACAAI).

That can include itching, swelling or even hives (though in rare cases, a person can also experience a severe allergic reaction like anaphylaxis). Raw celery, melons, oranges and peaches can have the same effect.

The problem, called pollen food allergy syndrome or oral allergy syndrome, happens when the immune system recognizes proteins in certain fruits and vegetables as similar to pollen.

The effect only happens from raw fruits and veggies, though; cooking denatures the foods' proteins, so the immune system no longer sees the proteins as a threat.

It's a good idea to let your doctor know if you consistently experience negative symptoms from eating any type of food — tomatoes or otherwise. Together, you can decide if it's worth temporarily eliminating the suspected offender to see if that helps you feel better.

Similarly, if your RA symptoms are decreasing your quality of life, work with your doctor to come up with a treatment plan that will help you better manage them.