What Seafood is Not Gluten-Free? Understanding Hidden Gluten

October 23, 2025 •

3 min read

While fresh, unprocessed seafood is naturally gluten-free, a Canadian Food Inspection Agency survey found undeclared gluten in a percentage of prepackaged processed fish and seafood products. For individuals with celiac disease or gluten sensitivities, understanding what seafood is not gluten-free is crucial for navigating menus and grocery store aisles safely.

Quick Summary

This guide details the specific types of seafood preparations and dishes that contain gluten, including breaded fish, imitation crab, and dishes with gluten-based sauces. It also explains the risks of cross-contamination in restaurants and how to read labels to ensure safe seafood consumption.

Key Points

Processed seafood is a major risk: Many imitation and pre-prepared seafood items, like imitation crab (surimi), contain gluten from wheat starch or fillers.
Breading and batters are common gluten sources: Fried seafood dishes, such as fish and chips, fish sticks, and fried shrimp, are typically made with wheat flour or breadcrumbs and are not gluten-free.
Sauces and marinades often contain hidden gluten: Soy sauce (found in many sushi and stir-fry dishes), teriyaki glazes, and some creamy sauces or marinades frequently use wheat-based ingredients.
Cross-contamination is a serious restaurant risk: Sharing fryers, cooking surfaces, and utensils in restaurants can transfer gluten to otherwise safe seafood.
Always check labels on packaged products: Even pre-seasoned or marinated fresh seafood can contain gluten, so scrutinize ingredients lists for any wheat derivatives or fillers.
Safe seafood means fresh and unprocessed: The safest option is to buy fresh, whole fish and shellfish and prepare it at home with gluten-free ingredients to control for all potential sources of contamination.

Common Gluten Traps in Seafood Dishes

Naturally, all fresh and unseasoned fish, shellfish, and mollusks are gluten-free. The danger lies in how seafood is prepared, processed, and packaged. For those with celiac disease or a gluten sensitivity, vigilance is key, especially with these common culprits:

Breaded and Fried Seafood

One of the most obvious sources of gluten in seafood is the breading used for frying. Dishes like fish and chips, fried shrimp, calamari, and fish sticks typically use wheat flour and breadcrumbs to create a crispy coating. Unless specifically labeled and prepared as 'gluten-free,' all fried seafood should be considered unsafe. The risk is compounded by the use of shared fryers in restaurants, which leads to gluten cross-contamination even if a gluten-free batter is used.

Imitation Seafood Products

Imitation crab meat, often labeled as surimi, is a highly processed seafood product that frequently contains gluten. It is made from minced fish paste mixed with fillers, binders, and flavorings, which often include wheat starch or other gluten-containing ingredients. This poses a significant risk in sushi rolls, seafood salads, and other dishes where real crab might be substituted. While some brands offer gluten-free versions, it is critical to read labels carefully and avoid imitation crab at restaurants where the brand cannot be confirmed.

Sauces, Marinades, and Seasonings

Many sauces and marinades used to prepare seafood contain gluten. Soy sauce, a staple in many Asian-inspired seafood dishes and sushi, traditionally contains wheat. Teriyaki sauce, often used for glazed fish, also typically contains soy sauce and is therefore not gluten-free. Other less obvious sources include certain fish sauces that may use hydrolyzed wheat protein and cream-based sauces thickened with flour. Even seemingly simple pre-seasoned or marinated seafood from a grocery store counter or butcher can contain hidden gluten.

The Silent Threat of Cross-Contamination

Cross-contamination is a serious concern, particularly for individuals with celiac disease. In both commercial kitchens and home settings, gluten can be inadvertently transferred from gluten-containing foods to naturally gluten-free seafood. Common scenarios include:

Shared Cooking Surfaces and Utensils: Using the same cutting boards, knives, or grills for both breaded fish and fresh seafood can transfer gluten particles.
Shared Fryer Oil: As mentioned, restaurants often use the same oil to fry both gluten-containing and gluten-free items.
Buffet Lines and Bulk Bins: Shared scoops and tongs can transfer gluten, making buffet-style seafood displays risky.
Pre-packaged and Display Case Seafood: Fish displayed next to breaded options in a supermarket case can become contaminated through shared surfaces or tools.

Essential Precautions for a Gluten-Free Seafood Diet

To ensure your seafood is safe, follow these essential guidelines:

Read Labels Thoroughly: Never assume a product is safe. Check ingredient lists for wheat, barley, rye, malt, and wheat starch.
Choose Fresh and Whole: Opt for fresh, unprocessed fish fillets, shellfish, or whole fish. Prepare it yourself at home to control all ingredients.
Ask Questions at Restaurants: When dining out, inform the staff about your gluten-free needs. Inquire about how dishes are prepared, what ingredients are in sauces, and if separate surfaces and fryers are used.
Consider Making Your Own Sauces: Prepare marinades and sauces at home using safe ingredients like tamari (gluten-free soy sauce) and gluten-free flour for thickening.

Comparison Table: Gluten-Free vs. Not Gluten-Free Seafood


Seafood Type	Preparation	Gluten Status	Potential Issues
Cod	Fresh Fillet	Gluten-Free	Cross-contamination at seafood counter
Cod	Breaded Fish Stick	Not Gluten-Free	Wheat breading, shared fryer
Crab	Freshly Steamed	Gluten-Free	None, if prepared separately
Crab	Imitation Crab (Surimi)	Not Gluten-Free	Wheat starch filler, undisclosed ingredients
Shrimp	Boiled with spices	Gluten-Free	Contaminated spices, cross-contamination
Shrimp	Fried Popcorn Shrimp	Not Gluten-Free	Wheat batter, shared fryer
Sushi	Simple, with fresh fish	Gluten-Free	Soy sauce, marinated fish glaze, cross-contamination
Sushi	Tempura Roll	Not Gluten-Free	Wheat-based tempura batter
Eel (Unagi)	Glazed	Not Gluten-Free	Glaze may contain wheat-based soy sauce

Conclusion

While the natural state of seafood is inherently gluten-free, the modern preparation and processing methods introduce numerous risks for those with gluten sensitivities. From obvious sources like breaded coatings and imitation seafood to the hidden dangers in sauces, seasonings, and restaurant kitchen cross-contamination, a proactive approach is necessary. By focusing on fresh, whole seafood and diligently checking all ingredients, individuals can enjoy the nutritional benefits of seafood safely while on a gluten-free diet. Educating oneself about potential gluten traps is the most effective way to prevent exposure and maintain a healthy dietary lifestyle. For further information and resources on living with celiac disease, visit Beyond Celiac's website.

Frequently Asked Questions

Yes, all fresh and unprocessed fish is naturally gluten-free. However, the risk comes from how it's handled, prepared, or what ingredients are added to it, particularly in restaurant or packaged settings.

Imitation crab (surimi) is a processed paste made from fish and other ingredients, often including wheat starch as a binder. This wheat starch is a gluten-containing ingredient.

You must be cautious. Even if the seafood itself is not breaded, it could be cooked in a shared fryer that has been used for breaded items like fish and chips. This leads to cross-contamination with gluten.

Traditional soy sauce is not gluten-free as it is brewed with wheat. You should always ask for gluten-free soy sauce, also known as tamari, which is made without wheat.

You must read the label carefully. While traditional fish sauce is often gluten-free, some modern versions or brands may include hydrolyzed wheat protein. Look for brands that are explicitly certified gluten-free.

When dining out, ask the staff if they use separate cutting boards, utensils, and dedicated fryers for gluten-free orders. Be explicit about your dietary needs to ensure they understand the risks.

Yes, you can make your own breaded seafood at home using gluten-free breadcrumbs, cornstarch, or crushed gluten-free crackers. Many restaurants that cater to celiac diets also offer dedicated gluten-free options.