Tomatoes are a popular and versatile fruit (yes, fruit!) packed with nutrients like vitamin C and antioxidants. However, for some people, tomatoes and related foods, such as tomato soup or sauce, can cause an upset stomach or other digestive symptoms, including diarrhea.
Here are four reasons why tomatoes hurt your stomach and how to manage them.
1. You Have a Food Intolerance
A food intolerance is a reaction to a food. It is similar to an allergy but much less severe and not life-threatening, and it comes from the digestive system.
Some people simply don't break down certain foods with FODMAPs, which causes havoc in the gastrointestinal tract. FODMAPs stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols; they are short-chain carbs that include fructans, lactose, fructose, sorbitol, and mannitol. These types of foods are notorious for causing digestive upset.
Tomatoes have the FODMAP fructose, a natural sugar, and some people have fructose malabsorption or fructose intolerance. The poorly digested fructose gets fermented by gut bacteria, says Ray Scott Daugherty, MD, who specializes in treating colorectal diseases, which can lead to upset stomach symptoms:
Poor absorption of fructose is thought to be one of the dietary triggers for irritable bowel syndrome and could be the reason why tomatoes give you diarrhea.
But keep in mind that a little tomato here and there may be fine. "Small amounts of tomatoes may not cause a problem, but where some people get tripped up is with canned tomatoes or other tomato-based products like ketchup and pasta sauce," says dietitian Kristin West, RD. "These other products tend to have additives like high-fructose corn syrup or garlic, and that can take you into the high-FODMAP zone."
So if you were wondering why tomato sauce gives you diarrhea or hurts your stomach, these ingredients could be to blame. Tomato soups and juices can also contain additives that your stomach may not agree with, so be sure to read the labels.
Fix it: If symptoms become problematic, it's best to have your doctor or a dietitian help you plan a diet around your restrictions so you can avoid an upset stomach and diarrhea after eating tomatoes.
2. You Have a Food Allergy
A food allergy can be a serious, potentially life-threatening condition. When you're allergic to a food, your immune system mistakenly identifies the food (or a component in the food) as harmful and responds in overdrive. About 33 million Americans have a food allergy.
Tomato allergies are said to partially "originate from pollen cross-reactivity," according to a study published in 2022. People who are allergic to birch pollen may also be at a higher risk for a tomato allergy because the main protein in birch pollen is similar to the protein in tomatoes.
In response to an allergen, antibodies, histamines, and other chemicals are released into the bloodstream, which cause symptoms. According to Ashley Kravitz, RD, owner of Nutrition Specialists of New Jersey, these symptoms might include the following on the skin or mouth:
Tingling
Itching
Numbness
Redness
It's also possible that an allergy to tomatoes could cause diarrhea and symptoms similar to those of fructose intolerance, she says:
Abdominal cramps
Nausea
Vomiting
Diarrhea
Fix it: It can be easy to confuse a food allergy with a food intolerance. If you have any of the above symptoms after eating tomatoes, see your doctor or an allergist, who can help you figure out the root cause.
If you experience difficulty breathing, trouble swallowing, a swollen throat, chest tightness, or severe hives, seek immediate medical attention.
3. It's Actually Heartburn
Consuming excessive amounts of tomatoes may trigger heartburn, which is a symptom of acid reflux. It's an uncomfortable burning sensation in your chest due to an irritated esophagus that's caused by stomach acid. It can happen at any time, but it's usually worse soon after you eat.
"Many people experience heartburn after consuming tomatoes because of their strong acidity. The human gastrointestinal tract produces gastric acid to break down foods that are sitting in your stomach, and when you consume acidic foods such as tomatoes, it can cause heartburn to act up," Kravitz says.
The discomfort may feel like an upset stomach, but the pain could actually be coming from an irritated throat. Other symptoms of acid reflux can include the following:
Coughing
Problems swallowing
The feeling of food caught in your throat
Sore throat
Hoarse voice
Vomiting
Fix it:Heartburn can usually be managed with over-the-counter meds and other acid reflux remedies like eating smaller portions and remaining upright for a couple of hours after eating. If you frequently experience heartburn, consult a doctor who can help identify the cause and develop a personalized treatment plan.
4. You've Got Food Poisoning
Food poisoning can occur when you drink or eat food contaminated with bacteria, toxins, parasites, mold, or viruses. Tomatoes can become contaminated with salmonella, shigella, or Escherichia coli (E. coli) during their growth in soil or at any stage of harvesting, processing, storage, shipping, or final preparation.
Food poisoning from tomatoes can cause diarrhea, along with upset stomach and the following other symptoms:
Diarrhea
Fever
Vomiting
Stomach cramps
Dehydration
Botulism is a serious type of food poisoning that's caused by a toxin that attacks the nerves in your body and can lead to paralysis, but it can also induce stomach issues such as vomiting, nausea, diarrhea, and stomachache. People who eat home-canned tomato sauce are at risk for botulism due to the improper canning of overripe or spoiled tomatoes, underprocessing, and incomplete seals.
See a doctor immediately if vomiting and diarrhea last more than two days, or if you have bloody stool, a high fever, confusion, worrisome stomach pains, or signs of botulism: muscle weakness, headache, blurred vision, upset stomach, and trouble breathing.
The Takeaway
Tomatoes are an excellent source of vitamin C and antioxidants.
In some people, tomatoes can lead to an upset stomach or other digestive symptoms because of a food intolerance, allergies, food poisoning, or heartburn.
If you experience discomfort from tomatoes, speak to your doctor about prevention or a treatment plan.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
Food allergy vs. food intolerance: What's the difference? Mayo Clinic. February 28, 2024.
Ali Y et al. Nutritional Composition and Bioactive Compounds in Tomatoes and Their Impact on Human Health and Disease: A Review. Foods. December 26, 2020.
Mayo Clinic Staff. Food Allergy. Mayo Clinic. August 30, 2024.
Kayli Anderson has over a decade of experience in nutrition, culinary education, and lifestyle medicine. She believes that eating well should be simple, pleasurable, and sustainable. Anderson has worked with clients from all walks of life, but she currently specializes in nutrition therapy and lifestyle medicine for women. She’s the founder of PlantBasedMavens.com, a hub for women to get evidence-based, practical, and woman-centered guidance on nutrition and cooking, hormone health, fertility, pregnancy, movement, mental well-being, nontoxic living, and more.
Anderson is board-certified in lifestyle medicine and serves as lead faculty of the American College of Lifestyle Medicine’s (ACLM) "Food as Medicine" course. She is past chair of the ACLM's registered dietitian member interest group, secretary of the women's health member interest group, and nutrition faculty for many of ACLM's other course offerings. She is the coauthor of the Plant-Based Nutrition Quick Start Guide and works with many of the leading organizations in nutrition and lifestyle medicine to develop nutrition content, recipes, and educational programs.
Anderson frequently speaks on the topics of women’s health and plant-based nutrition and has coauthored two lifestyle medicine textbooks, including the first one on women’s health, Improving Women's Health Across the Lifespan.
She received a master's degree in nutrition and physical performance and is certified as an exercise physiologist and intuitive eating counselor. She's a student of herbal medicine and women's integrative and functional medicine. She lives with her husband in the Colorado Rocky Mountains, where you’ll find her out on a trail or in her garden.
Christine Mugnolo is an experienced editor, wife, mom and certified instructor at a MAX Challenge in New Jersey. With health, nutrition and fitness in mind, she's an adventurous eater who is just trying to teach her kids (and dogs) that a Happy Meal is not a food group.
