Creamy tuna salad layered with crisp lettuce and juicy tomato on low FODMAP bread makes this Low FODMAP Tuna Salad Sandwich a simple, satisfying option for busy days.
I simply love this Low FODMAP Tuna Salad Sandwich. It’s quick to make, satisfying, and made with simple ingredients that work wonderfully together.
Tuna, mayonnaise, olives, and green onion create a creamy and savoury filling, while Dijon mustard adds extra flavour. Combined with fresh lettuce, tomato, and low FODMAP bread, it makes an easy lunch.
Being Italian, I am a big fan of olives. I enjoy all varieties, but I tend to favour black olives because of their richer flavour. Kalamata olives pair particularly well with tuna and are one of my favourite additions to this sandwich.
To keep this sandwich low FODMAP, choose a mayonnaise made without onion or garlic and use your preferred low FODMAP bread. I particularly enjoy making it with spelt sourdough.
If you aren’t following a low FODMAP diet, feel free to use your favourite mayonnaise and bread. You can also replace the green onion with finely sliced red onion for a slightly sharper flavour.
Why We Love This Tuna Sandwich
- Busy weekdays feel a little easier when a simple sandwich can double as a complete meal.
- Everyday ingredients make it easy to keep everything on hand for last-minute lunches.
- Portable servings work well for packed lunches, picnics, road trips, and outdoor meals.
Key Ingredients for Tuna Salad Sandwich
Tuna in Olive Oil
Tuna gives the filling its savoury flavour and flaky texture. Tuna packed in olive oil tends to remain moist after mixing and creates a creamier consistency.
Low FODMAP Mayonnaise
Mayonnaise creates a smooth, creamy texture and helps coat the tuna evenly. Choose a mayonnaise made without onion or garlic to keep the recipe low FODMAP.
Dijon Mustard
Dijon mustard adds tang and depth. A small amount balances the richness of the mayonnaise and complements the tuna.
Kalamata Olives
Kalamata olives add a savoury, slightly briny flavour and a firmer texture. Look for plump olives with a deep purple colour for the best flavour.
Green Onion
The green part of the onion adds a mild onion flavour and freshness. It provides a lighter alternative to regular onion in low FODMAP recipes.
Find the complete list with measurements in the recipe card below.
How to Make Low FODMAP Tuna Salad Sandwich
Step 1: In a medium bowl, combine the tuna, cucumber, green onion, and olives.
Step 2: Add the mayonnaise and Dijon mustard to the tuna mixture. Stir until evenly combined.
Step 3: Spread the tuna salad over two bread slices. Top with tomato slices and lettuce, then cover with the remaining bread slices to form the sandwiches.
Step 4: Serve immediately, or chill until ready to serve.
Frequently Asked Questions
You can replace the cucumber with finely diced celery, dill pickles, or capsicum for a different texture. Sliced avocado, extra lettuce, or additional tomato can also be included depending on your preference.
Yes, although the filling may be slightly less rich. Drain the tuna well before mixing it with the remaining ingredients.
Any low FODMAP bread will work. Spelt sourdough is a popular choice, but use your preferred variety based on your dietary needs and personal preference.
Yes, the cucumber is optional. The sandwich will still have a creamy texture, although it won’t have the same crunch.
Extra Help from the Kitchen
Pat the Cucumber Dry – Remove excess moisture from the diced cucumber before mixing it into the tuna salad to help keep the filling creamy.
Choose Firm Tomatoes – Use firm, ripe tomatoes rather than very juicy ones to reduce excess moisture in the sandwich.
Let the Filling Chill – Refrigerate the tuna salad for 15–20 minutes before assembling the sandwiches to give the ingredients time to meld.
Slice the Olives Thinly – Thinly sliced olives distribute more evenly through the filling and prevent larger pieces from ending up in one part of the sandwich.
Layer the Lettuce First – Place the lettuce on the bread before adding the tuna salad if preparing the sandwiches ahead. This creates a barrier between the filling and the bread, helping the sandwich stay fresher for longer.
Variations and Twists
Replace the Kalamata Olives with Capers – Swap the olives for 1–2 tablespoons of drained capers. Capers are smaller than olives, so they distribute more evenly through the tuna mixture and give the filling a saltier taste.
Replace the Cucumber with Celery – Use an equal amount of finely diced celery instead of cucumber. Celery stays crisp for longer after mixing and gives the sandwich more crunch.
Replace Part of the Mayonnaise with Avocado – Substitute half of the mayonnaise with mashed ripe avocado before mixing the filling. This creates a thicker tuna salad and reduces the amount of mayonnaise needed.
Use Red Onion Instead of Green Onion – Replace the green onion with 2–3 tablespoons of finely diced red onion if low FODMAP requirements aren’t a concern. For a milder flavour, soak the onion in cold water for 10 minutes before adding it to the tuna mixture.
Make a Tuna Melt – Top the tuna salad with sliced cheddar, Swiss, or provolone cheese before closing the sandwich. Toast in a sandwich press or skillet until the bread is golden and the cheese has melted.
Storage and Shelf Life
Store the tuna salad filling in an airtight container in the refrigerator for up to 2 days. If you’re preparing it ahead, keep the filling separate from the bread, lettuce, and tomato to maintain their texture.
Freezing isn’t recommended, as mayonnaise-based fillings can separate and become watery after thawing. If the sandwich has already been assembled, it’s best enjoyed within a few hours, as the vegetables can release moisture and soften the bread. This sandwich is best served chilled.
More Sandwich Recipes to Try
Low FODMAP Tuna Salad Sandwich Recipe
Equipment
Ingredients
- 140 g – 5 oz tuna in olive oil – drained
- 2 tbsp low FODMAP mayonnaise
- 2 tsp Dijon mustard
- ¼ cup cucumber – diced (optional)
- 1 tbsp green onion – green part only
- 2 tbsp Kalamata olives – sliced
- 4 slices low FODMAP bread
- tomato slices
- lettuce
Instructions
- In a medium bowl, combine the tuna, cucumber, green onion, and olives.
- Add the mayonnaise and Dijon mustard to the tuna mixture. Stir until evenly combined.
- Spread the tuna salad over two bread slices. Top with tomato slices and lettuce, then cover with the remaining bread slices to form the sandwiches.
- Serve immediately, or chill until ready to serve.
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