Plain tomatoes are low FODMAP, but most tomato soups are not. The problem isn’t the tomato itself. It’s everything else in the bowl: onion, garlic, wheat flour, cream, and stock made with high FODMAP ingredients. Whether you’re buying canned soup or making it from scratch, the recipe matters far more than the base ingredient.
Why Plain Tomatoes Are Safe
Fresh tomatoes, canned tomatoes, and tomato paste are all low FODMAP in typical serving sizes. Monash University, the research group behind the FODMAP diet, has tested tomatoes and confirmed they contain minimal amounts of the fermentable sugars that trigger IBS symptoms. A standard serving of common tomato (about 75 grams) sits comfortably in the low FODMAP range.
This means tomato soup has a perfectly safe foundation. The issues start when cooks and manufacturers build on that foundation with ingredients that aren’t so friendly.
What Makes Store-Bought Tomato Soup High FODMAP
Most commercial tomato soups contain multiple high FODMAP ingredients. Campbell’s Creamy Tomato Soup, for example, lists wheat flour, whey protein concentrate, cream, and garlic oil among its ingredients. The Spoonful app flags it as not low FODMAP, identifying two ingredients that are likely high FODMAP per serving and six more that could be moderate or high depending on the source or amount.
The most common offenders in canned and boxed tomato soups include:
- Onion and garlic (in any form: powder, flakes, or whole) are among the highest FODMAP ingredients in the Western diet, loaded with fructans
- Wheat flour, often used as a thickener, contains fructans as well
- Cream, milk, or whey, which add lactose
- Chicken or vegetable broth, which frequently contains onion and garlic even when the label just says “natural flavoring”
If you’re in the elimination phase of the low FODMAP diet, reading ingredient labels closely is essential. Onion and garlic hide under vague terms like “spices,” “natural flavoring,” or “vegetable extract.” Even organic or health-branded soups often rely on onion and garlic as their primary flavor base.
Certified Low FODMAP Options
A small number of brands make tomato soups that carry a low FODMAP certification. Bay’s Kitchen produces a Tomato and Roasted Pepper Soup that is certified FODMAP Friendly, and their full soup line is also gluten free, dairy free, and vegan. Products with a FODMAP Friendly or Monash University certification logo have been laboratory tested to confirm they fall within safe thresholds per serving.
These certified products are the safest store-bought option during the elimination phase. Without that certification, you’re relying on your own label reading, which can miss hidden FODMAPs in broths and seasoning blends. If a certified brand isn’t available near you, making your own soup gives you full control over what goes in.
How to Make Tomato Soup Low FODMAP
A homemade low FODMAP tomato soup is straightforward once you know which swaps to make. The base stays the same: canned tomatoes or tomato paste, cooked down with liquid until smooth. The changes are all about replacing the usual flavor builders with safe alternatives.
The biggest challenge is replacing onion and garlic, since they do most of the heavy lifting in a traditional recipe. Two reliable solutions exist. First, garlic-infused oil and onion-infused oil. The fructans in garlic and onion are not oil-soluble, so when you heat whole garlic cloves or onion pieces in oil and then remove them, the flavor transfers but the FODMAPs stay behind. You can make these at home or buy commercial versions. Second, the green parts of scallions (spring onions) are low FODMAP according to Monash University testing and add a mild onion-like flavor. About a cup of chopped scallion greens works well sautéed at the start of the soup.
For thickening, skip wheat flour entirely. Cornstarch, potato starch, or simply blending the soup smooth with an immersion blender all create a rich, creamy texture without adding fructans. If you want a cream-of-tomato style, use lactose-free cream, coconut cream, or a splash of lactose-free milk instead of regular dairy.
For the liquid base, choose your broth carefully. Not all broths are safe. Many contain onion and garlic in their ingredient lists. Campbell’s chicken broth has been identified as low FODMAP, but other brands vary widely. During the elimination phase, stick with a broth you’ve confirmed is free of FODMAP ingredients, or use plain water supplemented with the infused oils and herbs for flavor.
Serving Size Still Matters
Even with a homemade low FODMAP recipe, portion size plays a role. Tomato paste, while low FODMAP in moderate amounts, can become moderate at larger servings (roughly two tablespoons is the tested safe threshold). If your recipe uses a lot of paste for a concentrated flavor, keep your bowl size reasonable. The same principle applies to any ingredient that’s low FODMAP only up to a certain amount.
Stacking is another consideration. If you’re eating tomato soup alongside bread, cheese, or other foods that each contain small amounts of the same FODMAP type, those amounts can add up and push you past your tolerance threshold even though each food was technically safe on its own. This is especially relevant during the elimination phase, when you’re still mapping out your personal limits.
Quick Ingredient Checklist
Whether you’re scanning a label or building a recipe, here’s what to look for and avoid:
- Safe: tomatoes, tomato paste (up to 2 tablespoons), garlic-infused oil, onion-infused oil, scallion greens, cornstarch, lactose-free cream, olive oil, salt, pepper, fresh basil
- Avoid: onion (any form), garlic (any form except infused oil), wheat flour, regular cream or milk, broths with unlisted or unclear seasonings, high fructose corn syrup
If a store-bought soup lists any form of onion or garlic in the actual ingredients rather than as an infused oil, it’s not safe for the elimination phase. Once you’ve completed reintroduction testing and know your personal tolerances, you may find you can handle small amounts of these ingredients, but that varies widely from person to person.