1. Soy sauce and wasabi
This is basic but very important to know and keep in mind – standard soy sauce contains wheat! Gluten-free soy sauce and tamari are great substitutes that taste incredibly similar. Some Japanese restaurants may have GF soy sauce available if you ask, but always double-check when dishes are made with soy sauce. In addition, some packaged wasabi uses wheat starch as a thickener.
Not only is there wheat flour in batter used for tempura dishes, but tempura flakes (also known as “crunch”) that are used as a topping on sushi rolls have wheat as well. In addition, keep in mind that if a restaurant offers tempura, there’s a good chance they are using the same fryer for tempura as well as other dishes, so be sure to ask about potential cross-contamination.
3. Imitation Crab
Imitation crab (also known as “crab stick”) almost always contains wheat starch as a binding agent. This is why California rolls – which usually use imitation crab – are almost never gluten-free. Always ask about ingredients if there is any sort of imitation crab or fish in a dish.
4. Sauces and Dressings
Soy sauce and wheat starch are often in dressings and sauces. Watch out for seaweed salad especially – it almost always has soy sauce in the dressing.
5. Fish Roe
Some fish roe (e.g., those orange fish eggs used as a sushi topping) have an added wheat thickener to help bind the eggs together. This isn’t always for the case, but it’s worth checking.
Believe it or not, some restaurants use steam from boiling wheat-based noodles to cook edamame and other vegetables. This can potentially cause cross-contamination. While this practice won’t be used at all Japanese restaurants, it is worth double-checking to be sure.