Tomatoes are not likely to cause excessive gas for most people.
It’s possible for them to cause gas in people who are particularly sensitive to fructose, or have a rare intolerance to foods from the nightshade family.
However, in most cases, it’s more likely that any gas that most people experience after eating tomatoes comes from another food consumed alongside them.
I’ll explain why in this short post.
Table of Contents
How Vegetables (or Fruits) Like Tomatoes Cause Gas
Part of the reason I wrote this post is because I came across a lot of misinformation on the topic.
Several blog posts I saw claimed that tomatoes are an acid food which increased stomach acid production that somehow leads to gas. This is just incorrect.
There are 3 sources of gas that leads to flatulence or burping, and stomach acid has nothing to do with it unless it changes your breathing habits:
- Swallowed air
- Gas produced in the gut
- Gas diffused from blood to the gut
The actual reason that vegetables and fruits often cause gas is because they contain hard to digest carbohydrates.
This includes carbohydrates like fiber, which don’t break down in the stomach or small intestine at all. When these carbohydrates go to the large intestine, they are fermented by your gut bacteria, which produces gas.
If this gas is trapped, it causes bloating until it is released, primarily through flatulence.
Fiber Content of Tomatoes
While there are multiple types of carbohydrates that are difficult to digest and can end up producing gas in the large intestine, fiber is the most well known.
So let’s start by looking at the macronutrient profile of tomatoes per 100 grams, which is about 1 small tomato (not the grape sized ones).
| Tomato | |
|---|---|
| Energy (kcal) | 18 |
| Protein (g) | 0.88 |
| Total Lipid (g) | 0.2 |
| Carbohydrate (g) | 3.89 |
| Fiber (g) | 1.2 |
| Sugars (g) | 2.63 |
A typical meal for most people could include about 1-3 of these servings, so 1.2-4 grams of fiber in total.
While this can result in a little bit of gas production, it shouldn’t lead to excessive flatulence. For reference, adults are supposed to eat at least 20 grams of fiber per day, and some foods like beans have way more than tomatoes.
Other Tough Carbohydrates to Digest in Tomatoes
Most of the other carbohydrates that lead to fermentation are classified as FODMAPs.
I’ve pulled this data for tomatoes from a study, and it turns out that tomatoes basically have no FODMAPs besides fructose.
After removing carbohydrates that couldn’t be detected, the carbohydrate profile of tomatoes looks like this per 100 grams:
| Tomato, common | |
|---|---|
| Moisture | 92 g |
| Fructose | 1.28 g |
| Glucose | 1.66 g |
| Sucrose | 0.17 g |
Note that sucrose is literally just a molecule of fructose combined with glucose.
While glucose is easily digested, fructose malabsorption is quite common, and tomatoes are relatively high in fructose. Fructose is harder to digest than glucose to begin with, but it’s extremely difficult for some people and leads to side effects like bloating and flatulence.
One study found that just about everyone can absorb 15 grams of fructose, but some people started having trouble at amounts greater than that.
With that being said, tomatoes really aren’t that high in fructose.
Even if we combine the fiber and fructose amounts, it’s about 2.5 grams of hard to digest carbohydrates per serving. Unless you’re eating 5+ servings, it’s unlikely that it’s enough to gas on its own.
Other Explanations and What to Do About Gas From Tomatoes
In most cases, any gas from a meal that can be high in tomatoes (i.e. chili, curries) is likely due to a different ingredient in them (e.g. beans).
However, there is one more possible explanation: a nightshade allergy or intolerance.
Foods like tomatoes, white potatoes, eggplants, and bell peppers are all part of the nightshade plant family.
While this is commonly discussed in the “paleo diet” community, there’s not much published research on this topic, aside from a few rare case reports. In addition, these allergies typically have other more obvious symptoms than gas, like joint pain or itchy skin.
