Can Eating Tomatoes Upset Your Stomach?

Top view of fresh salad vegetable and   shrimp on bowl with castard
Though the tomato is highly nutritious, it may be the cause of stomach pain for some. (Image: Dokmaihaeng/iStock/Getty Images)

Tomatoes are a popular food -- eaten fresh as a summer favorite, and found in a variety of different foods and drinks, such as spaghetti sauce, vegetable juices, lasagna, pizza, soups and salads. This food -- functionally a vegetable but scientifically a fruit -- is consumed worldwide for its health benefits and delicious taste. Tomatoes are one of the leading sources of the antioxidant lycopene and and also contain a high amount of vitamin C. In some people, due to intolerance or allergy, tomatoes can lead to stomach upset.

Intolerance

Tomatoes contain a high amount of acidity, and if you suffer from heartburn or acid reflux, tomatoes can cause irritation. This may feel like stomach upset, however most likely this pain is from the esophagus getting exposed to acidic stomach contents. If you have acid reflux, tomatoes only need to be avoided if they aggravate your symptoms.

Tomatoes contain fructose, a natural sugar, and some people have fructose malabsorption or fructose intolerance. While small amounts of tomatoes may not cause a problem, larger amounts of fresh tomatoes or the concentrated tomatoes found in sauces or juice can provide more fructose -- even more if high fructose corn syrup is an added ingredient. The poorly digested fructose gets fermented by gut bacteria and causes symptoms such as nausea, abdominal pain, gas and diarrhea. Poor absorption of fructose is thought to be one of the dietary triggers for irritable bowel syndrome.

Allergy

According to the Food and Drug Administration, over 160 foods can cause an allergic response. While tomatoes are not a common allergen, an allergic reaction could be the cause of a variety of symptoms including stomach discomfort and cramps. According to a review published in the September 2013 issue of “Today’s Dietitian,” sometimes these rare allergic responses to fruits and vegetables is really an environmental allergy -- such as a pollen allergy contaminating the fruit, or proteins from different plants similar enough to confuse the immune system and cause cross-reactivity. Tomatoes can also be linked to a latex allergy. According to a report in the November 2002 issue of “Biochemical Society Transactions,” 30 to 50 percent of people with latex allergy have an associated allergy to a scientifically-related food, and tomatoes one of the foods known to cause this cross-reactivity. If you suspect you have an allergy to tomatoes, get advice and treatment recommendations from your doctor.

Hidden Culprits

If you have an upset stomach after eating tomatoes, sometimes another food is to blame. For example, if you eat a meal of lasagna, garlic bread, and wine -- the tomato sauce may not be the problem. High fat meals, such as lasagna and buttery garlic bread can slow stomach emptying, keeping food in your stomach longer and making nausea or indigestion more likely. Alcoholic beverages can also cause these symptoms, particularly when paired with a high fat meal. Sometimes the symptoms are more likely when you lie down right after eating. It may help to keep a food diary with your symptoms to help determine which food, or which types of meals trigger your symptoms.

Precautions and Next Steps

Tomatoes are a nutritious food that can be enjoyed by most people. If you have stomach upset after eating, keep a food diary with your symptoms to help pinpoint the offending food. If you have pain or other uncomfortable symptoms after eating tomatoes, talk to your doctor. If you have an intolerance or allergy, your doctor can refer you to a dietitian to plan a nutritious diet around your restrictions. While tomato allergies are rare, allergies can be life-threatening. Talk to your doctor in advance about how to deal with medical emergencies. If you experience difficulty breathing, trouble swallowing, a swollen throat, chest tightness or severe hives, seek immediate medical attention.

Reviewed by: Kay Peck, MPH, RD

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