Plain fish is naturally free of FODMAPs. Because FODMAPs are specific types of carbohydrates, and fish is made up almost entirely of protein and fat, it contains virtually no FODMAPs regardless of the species. This applies to all fresh fish, from salmon and cod to tuna and tilapia. The complications start when fish is processed, marinated, breaded, or canned with other ingredients.
Why Fish Is Naturally FODMAP-Free
FODMAPs are short-chain carbohydrates found in certain plant foods, dairy products, and sweeteners. They show up in fruits, vegetables, grains, and legumes because those foods contain varying amounts of sugars like fructose, lactose, and sugar alcohols. Fish, like all meat and seafood, simply doesn’t contain these carbohydrates. There’s nothing in the flesh of a fish that can ferment in your gut the way a high FODMAP food would.
This means you can eat fresh fish in normal portions without worrying about triggering IBS symptoms from FODMAPs. The same is true for shellfish. Shrimp, lobster, crab, mussels, and scallops are all naturally low FODMAP for the same reason: their nutritional profile is protein and fat, with little to no carbohydrate content.
Canned Tuna and Hidden Ingredients
Canned fish is where things get tricky. Many major U.S. brands of canned tuna, including Bumble Bee, StarKist, and Chicken of the Sea, pack their tuna in vegetable broth rather than plain water or oil. The broth is added as a flavor enhancer to give the tuna a milder taste, but it may contain garlic or onion, both of which are high FODMAP. When companies are asked about the exact ingredients in their vegetable broth, they often can’t confirm what’s in the blend.
To stay safe, look for canned tuna packed in plain water, olive oil, or spring water. Check the ingredients list for “vegetable broth,” “natural flavors,” or “broth” and avoid those varieties during the elimination phase. Canned sardines and canned salmon tend to have simpler ingredient lists, but it’s still worth a quick label check.
Smoked, Cured, and Marinated Fish
Smoked salmon and other cured fish products can be FODMAP-safe, but many recipes and commercial products use garlic powder, onion powder, or both in the brine or cure. Some also include sugar or honey as part of the smoking process. A plain hot-smoked salmon with just salt is fine, but flavored or glazed varieties often contain high FODMAP seasonings that aren’t always obvious from the front of the package.
Marinated fish carries the same risk. Garlic and onion are the most common culprits, but some marinades also include honey, high-fructose corn syrup, or fruit juice concentrates that can push a serving into high FODMAP territory. If you’re buying pre-marinated fish from a deli or freezer section, read the full ingredient list before assuming it’s safe.
Breaded and Battered Fish to Avoid
Fish fingers, battered fish fillets, and any breaded frozen fish products are typically high FODMAP. The coating is almost always made with wheat flour, which contains fructans. Tempura batter is another common offender. Even crumbed fish and poultry fall into this category.
If you want a crispy coating, you can bread fish at home using gluten-free breadcrumbs or a rice flour coating. Just make sure the gluten-free product you choose doesn’t contain onion or garlic powder, which manufacturers sometimes add for flavor.
Watch Out for Imitation Crab
Imitation crab (surimi) looks like seafood but is a processed product made from fish paste mixed with fillers. It commonly contains wheat starch, potato starch, sugar, and sorbitol. Sorbitol is a sugar alcohol and a known high FODMAP ingredient that can trigger symptoms even in small amounts. If you’re following a low FODMAP diet, treat imitation crab as a processed food and read labels carefully rather than assuming it behaves like real shellfish.
Safe Ways to Season Fish
The biggest seasoning pitfall is anything labeled simply “spices” on an ingredient list, since that vague term can hide garlic or onion powder. When cooking fish at home, you have plenty of safe options. Salt, black pepper, paprika, smoked paprika, ground ginger, dry mustard, and ground cloves are all low FODMAP. Dill seed is low FODMAP in servings up to one teaspoon, and red pepper flakes (chili flakes) are safe at the same amount.
Fresh herbs like chives (green parts only), basil, cilantro, and parsley are all good choices. Lemon juice, olive oil, and butter work well for simple preparations. Garlic-infused oil is also a popular workaround on the low FODMAP diet, since the FODMAPs in garlic are water-soluble and don’t transfer into oil.
Quick Guide by Type
- Fresh fish (any species): Low FODMAP, no restrictions on type
- Fresh shellfish (shrimp, crab, lobster, scallops, mussels): Low FODMAP
- Canned fish in water or oil: Low FODMAP if no vegetable broth or flavorings added
- Canned fish in vegetable broth: Potentially high FODMAP due to garlic or onion
- Smoked or cured fish: Check for garlic powder, onion powder, and added sugars
- Breaded or battered fish: High FODMAP due to wheat coating
- Imitation crab: Often high FODMAP due to sorbitol and wheat starch
- Marinated or sauced fish: Check all ingredients individually
The simplest rule: the closer your fish is to its original, unprocessed state, the safer it is on a low FODMAP diet. A plain grilled fillet with olive oil, salt, and lemon will always be a reliable choice.