Tomatoes are a popular and versatile fruit (yes, fruit!) packed with healthy nutrients like vitamin C and antioxidants. But for some people, tomatoes and foods like tomato soup or tomato-based sauces can lead to an upset stomach.
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Here are four reasons why tomatoes can cause tummy troubles and other symptoms to look out for.
1. You Have a Food Intolerance
A food intolerance, according to the Mayo Clinic, is a reaction to a food similar to an allergy, but much less severe and not life-threatening — and it comes from the digestive system. Some people just don't break down certain foods that are on the FODMAP list well, and that causes GI tract havoc.
FODMAPs (which stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are short-chained carbs that include fructans, lactose, fructose, sorbitol and mannitol, according to Harvard Health Publishing. These types of foods are notorious for causing upset stomach.
And yes, tomatoes, unfortunately, are on the FODMAP list. They contain fructose, a natural sugar, according to Food Intolerance Diagnostics, 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 all colorectal diseases, which can lead to upset stomach symptoms including:
- Cramping and gas pains
Poor absorption of fructose is thought to be one of the dietary triggers for irritable bowel syndrome.
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. These other products tend to have additives like high-fructose corn syrup or garlic, and that can take you into the high-FODMAP zone," says dietitian Kristin West RD, LDN.
Tomato soups and juices can also have various ingredients your stomach doesn't agree with, so don't forget to read labels.
If symptoms become problematic, it's best to have your doctor or a dietitian help you plan a diet around your restrictions.
2. You Have a Food Allergy
A food allergy can be a serious, potentially life-threatening condition. About 32 million Americans have one, according to Food Allergy Research & Education. When you're allergic to a food, per the Mayo Clinic, your immune system mistakes the food (or something in the food) for something harmful and goes into overdrive.
A small 2013 study in the Journal of Investigational Allergology and Clinical Immunology concluded that tomato allergy happens from an overreaction to certain proteins in the fruit.
People who are allergic to birch pollen may also be at higher risk for a tomato allergy because the main protein in birch pollen is similar to the protein in tomatoes, according to the European Centre for Allergy Research Foundation.
In response to these proteins (the allergens), antibodies, histamines and other chemicals are released into the bloodstream, which cause allergy symptoms. According to dietitian Ashley Kravitz, RD, owner of Nutrition Specialists of New Jersey, these symptoms might include the following on the skin or mouth:
It's also possible to experience similar symptoms as you would to a fructose intolerance, she says, such as:
- Abdominal cramps
So 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 have difficulty breathing, trouble swallowing, a swollen throat, chest tightness or severe hives, seek immediate medical attention.
3. It's Actually Heartburn
Heartburn, according to the Cleveland Clinic, 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 GI 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 you're in may feel like an upset stomach, but the pain may actually be coming from an irritated throat. Other symptoms of acid reflux can include:
- Problems swallowing
- The feeling of food caught in your throat
- Sore throat
- Hoarse voice
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 hours after eating, but, if necessary, your doctor can prescribe something stronger.
4. You've Got Food Poisoning
Food poisoning happens when you eat food contaminated with bacteria or their toxins, parasites or viruses, according to the Gastrointestinal Society. Tomatoes can become contaminated with Salmonella, Shigella, or Escherichia coli (E. coli) during their growth in soil, or during harvesting, processing, storing, shipping or final preparation.
Along with upset stomach, symptoms can include:
- Stomach cramps
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, per the Centers for Disease Control and Prevention, but 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, under-processing and incomplete seals, per Colorado State University.
The Mayo Clinic recommends seeing a doctor immediately if vomiting and diarrhea last more than two days, you have bloody stool, a high fever, confusion, worrisome stomach pains or signs of botulism (muscle weakness, headache, blurred vision, upset stomach and difficulty breathing).
Is This an Emergency?
- Journal of the American Society for Horticultural Science: "Antioxidant Balance and Regulation in Tomato Genotypes of Different Color"
- Mayo Clinic: "Food Allergy Vs. Food Intolerance: What's the Difference?"
- Harvard Health Publishing: "Try a FODMAPs Diet to Manage Irritable Bowel Syndrome"
- Food Intolerance Diagnostics: "Fructose Content of Food"
- Ray Scott Daugherty, MD
- Kristin West RD, LDN
- Food Allergy Research & Education: "What Is a Food Allergy?"
- Mayo Clinic: "Food Allergy"
- Journal of Investigational Allergology and Clinical Immunology: "Tomato Allergy: Clinical Features and Usefulness of Current Routinely Available Diagnostic Methods"
- European Centre for Allergy Research Foundation: "The Right Tomato for People With Birch Pollen Allergy"
- Ashley Kravitz, RD
- Cleveland Clinic: "GERD (Chronic Acid Reflux)"
- Gastrointestinal Society: "Food Poisoning: Causes, Symptoms, & Treatments"
- Centers for Disease Control and Prevention: "Botulism"
- Colorado State University: "Canning Tomatoes and Tomato Products"
- Mayo Clinic: "Foodborne Illness"