Understanding FODMAPs and Tomatoes
FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are a group of carbohydrates that can cause digestive distress for some individuals, particularly those with Irritable Bowel Syndrome (IBS). While tomatoes contain FODMAPs, the amount varies depending on the variety, ripeness, and how they are processed. The FODMAP primarily found in tomatoes is fructose, which is a monosaccharide.
Fresh vs. Canned Tomato FODMAP Levels
It's important to understand how the processing of tomatoes affects their FODMAP content. Canned tomatoes can have different FODMAP levels than their fresh counterparts due to the concentration of sugars during the canning process.
- Fresh Roma/Plum Tomatoes: Monash University indicates that a small 48g serving is low FODMAP, while larger servings can quickly become moderate or high in fructose.
- Canned Roma/Plum Tomatoes: Lab testing shows that the FODMAP threshold for canned plum tomatoes is more generous, with a low FODMAP serving of 100g. The discrepancy is likely because some fructose leaches into the surrounding juice during the canning process.
Are Canned San Marzano Tomatoes Low in FODMAP?
San Marzano tomatoes are a variety of plum tomato known for their sweet flavor and low acidity. Since they are a plum tomato, the FODMAP guidelines for canned plum tomatoes apply. According to Monash University's extensive testing, canned plum tomatoes are low in FODMAPs when consumed in a serving of up to 100g (approximately 1/2 cup). Larger servings, such as 182g (1 cup), can contain moderate amounts of fructose.
This means that canned San Marzano tomatoes can be a staple in a low FODMAP kitchen. However, this relies on a crucial factor: the ingredients. For a canned tomato product to be truly low FODMAP, it must not contain any added high-FODMAP ingredients.
How to Choose a Low FODMAP Canned San Marzano Tomato Product
To ensure your canned San Marzano tomatoes are low in FODMAPs, follow these guidelines when shopping:
- Read the ingredients list carefully. Avoid products that contain garlic, onion, or high fructose corn syrup. Look for simple ingredients: just San Marzano tomatoes, tomato juice, and possibly salt, citric acid, or basil.
- Stick to the recommended serving size. Even with the right product, portion control is key. A 100g serving is the accepted low FODMAP amount. Overconsuming tomatoes can lead to FODMAP stacking and trigger symptoms.
- Look for products packed in juice, not puree. Monash University tests typically focus on products packed in juice. While some brands of plain tomato puree may be low FODMAP, checking the app for specific entries is recommended. Canned tomato paste is low FODMAP in a smaller, 28g portion.
Comparison: Common Tomato Products and Their FODMAP Content
| Product Type | Low FODMAP Serving Size (Approx.) | Key FODMAPs to Watch For | Notes |
|---|---|---|---|
| Fresh Roma Tomato | 48g (2/3 small tomato) | Fructose | Portion size is very small. |
| Fresh Common Tomato | 65g (1/2 medium tomato) | Fructose | Moderate levels begin at 75g. |
| Canned Roma/Plum (inc. San Marzano) | 100g (1/2 cup) | Fructose | Check for added high-FODMAP ingredients. |
| Canned Tomato Paste | 28g (2 tbsp) | Fructans | Concentrated, so higher FODMAP content overall. |
| Sun-Dried Tomatoes | 8g (3 pieces) | Fructose | Highly concentrated, so the serving is very small. |
| Jarred Pasta Sauce | Often high FODMAP | Fructans, GOS, Fructose | Frequently contains onion and garlic.. |
The Role of Canning in FODMAP Content
The canning process itself can influence the FODMAP profile of tomatoes. Heating tomatoes can cause a rise in fructose levels compared to their fresh state. However, the good news for canned whole tomatoes packed in juice is that the overall FODMAP level is still manageable within controlled portions. It's the concentration of the tomato product (like in tomato paste or sun-dried tomatoes) and the addition of high-FODMAP seasonings (like in jarred sauces) that pose the greatest risk for those with sensitive digestive systems.
Practical Tips for Using San Marzano Tomatoes on a Low FODMAP Diet
- Measure your portions. Use a kitchen scale to measure out your 100g serving of canned tomatoes to ensure accuracy. This is especially important during the elimination phase of the diet.
- Rinse and drain. If you're concerned about excess liquid contributing to FODMAP intake, you can drain the tomatoes, though Monash tests were based on products packed in juice.
- Make your own sauces. Homemade sauces are the best way to control all ingredients. Use a low FODMAP recipe and flavor with herbs like basil, oregano, and garlic-infused oil instead of fresh garlic.
- Save the rest. An open can of tomatoes can be frozen in individual 100g portions for future use. This prevents food waste and ensures you always have a ready-to-go, low FODMAP serving.
Conclusion: A Digestible Delight, in Moderation
Canned San Marzano tomatoes, being a type of canned plum tomato, are generally considered low in FODMAPs when a specific portion size is followed. The key to including them in your low FODMAP diet is careful label-reading to avoid added high-FODMAP ingredients and strict portion control. By measuring your servings and opting for simple, unseasoned products, you can enjoy the rich flavor of San Marzano tomatoes without triggering unpleasant digestive symptoms.
For more information on navigating the Low FODMAP diet, consult the official Monash University FODMAP App.
