Does Tomato Trigger IBS?
It depends on the type and the amount, and the numbers moved. Monash retested tomatoes and they are no longer unlimited: a common tomato is low-FODMAP at 65g, which is about half a medium one, and moderate by 75g. Cherry tomatoes are tighter still at 45g — roughly three. Canned tomatoes are the most generous at 100g. Plenty of older low-FODMAP guidance still calls tomatoes a free food, and that is out of date.
What Makes Tomato Problematic for IBS
Tomatoes carry fructose in excess of glucose, and the retest found more of it than the original testing did. The practical difficulty is that 65g is half a medium tomato, while recipes and salads treat tomatoes as a bulk ingredient. Cherry tomatoes are the easiest to overshoot because they are eaten by the handful and three is a smaller number than anyone expects. Sun-dried tomatoes and tomato paste concentrate the load further.
How it works
When a food contains more fructose than glucose, the surplus cannot use the fast glucose-coupled absorption route and depends on GLUT5 alone, which is slow and saturable. What is not absorbed moves into the colon, pulling water with it osmotically and feeding bacterial fermentation. That combination produces the bloating and loose stool characteristic of an excess-fructose load.
Common Symptoms
Reactions usually appear within a few hours and combine bloating with gas. Tomato acidity is a separate issue worth separating out: reflux and stomach discomfort after tomatoes is an acid effect, not a FODMAP one, and it will not improve by staying under the serving limit.
Portion Thresholds
Safe Portion
Common: 65g (half a medium). Cherry: 45g (about 3)
Research Reference
Monash University retested tomatoes and they are no longer unlimited. Common tomato is low-FODMAP at 65g, moderate at 75g and high at 91g. Cherry tomato is low at 45g, moderate at 60g and high at 75g. Canned tomato with juice is low at 100g, and roma is low at 75g.
Practical Tip
Canned tomatoes give you the most room at 100g, which is why a home-made passata sauce is easier to keep compliant than a salad full of fresh tomatoes. Count cherry tomatoes rather than eyeballing them — three is the serving. Sun-dried tomatoes and tomato paste are concentrated and should be treated as small additions. Use garlic-infused oil rather than whole garlic in any sauce.
Related Foods
It depends, and the number is smaller than almost anyone expects: Monash rates cherry tomatoes low-FODMAP at 45g, which is about three tomatoes. They reach moderate at 60g and high at 75g — roughly five. Cherry tomatoes are tighter than common tomatoes, which get 65g, and they are the easiest tomato to overshoot because they are eaten whole, by the handful, straight from the punnet.
It depends on how much of the tin you use, but this is the good news in the tomato family: Monash rates canned tomatoes in juice low-FODMAP at 100g, moderate at 138g and high at 186g. That is noticeably more generous than fresh — common tomato gets 65g and cherry only 45g — which makes canned the sensible base for sauces. The catch is that a standard 400g tin split between two people is 200g each, already past the high threshold.
It depends. Plain tomato sauce made from just tomatoes is low-FODMAP at up to half a cup (100g). However, most commercial tomato sauces contain garlic, onion, and added sugars that make them high-FODMAP. Always check labels or make your own sauce using garlic-infused oil and canned tomatoes.
It depends on the colour, and this one changed. Monash retested capsicum and downgraded it from unlimited: red is low-FODMAP at only 43g (about a third of a cup) and tests high for excess fructose by 75g — one cup. Green is far more forgiving, low at 75g and not high until around 310g. Yellow and orange have never been tested. If you have been treating all peppers as a free food, red is the one to rein in.
No. Carrots are considered low-FODMAP and are generally safe for people with IBS at all portion sizes. They are one of the most reliable safe vegetables on a low-FODMAP diet. Most people tolerate them well whether raw, cooked, or steamed, without experiencing bloating or other digestive symptoms.
Frequently Asked Questions
Are tomatoes safe for IBS?
Yes. Fresh tomatoes are low-FODMAP at one medium tomato per serving. If tomato dishes cause symptoms, check for garlic and onion in the recipe.
Are cherry tomatoes low-FODMAP?
Yes. Cherry tomatoes are low-FODMAP at up to 5 tomatoes per serving.
Is tomato paste low-FODMAP?
Tomato paste is more concentrated and becomes moderate-FODMAP at larger amounts. Use up to 2 tablespoons per serving.
Sources & References
FODMAP grade and serving-size data for Tomato are based on published research from Monash University, the institution that developed the low-FODMAP diet. To understand how this data fits into a structured protocol, see our complete elimination diet guide.
- Monash University — About FODMAPs & IBS
- Monash University — Starting the Low-FODMAP Diet
- Halmos et al. (2014) — Low-FODMAP diet reduces IBS symptoms (Gastroenterology)
- NIDDK (NIH) — Irritable Bowel Syndrome
FODMAP thresholds are updated as new research is published. If you notice a portion that no longer matches the latest Monash guidance, let us know and we will update the page.
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