In a Japanese kitchen, wheat is rarely the dish. It is the seasoning. It is in the soy sauce that goes into nearly every sauce, in much of the miso, in the tempura batter, in the little rounds of fu floating in a clear soup. That makes Japan harder for a gluten‑free diner than its rice‑based menus suggest — and it makes what you say before the meal matter more than anything you say at the table.
Our group is involved in running restaurants in Tokyo. This is written from the kitchen side: where wheat and barley actually turn up, which meals can be changed, and how to ask so that the answer is honest.
Where does the wheat hide in Japanese food?
Gluten is found in three cereals: wheat, barley and rye. In Japanese cooking, rye almost never appears. Wheat and barley do, in these places:
- Soy sauce. Under Japan’s agricultural standard (JAS), the most common type, koikuchi, is brewed from soybeans with roughly an equal amount of wheat; the light usukuchi is the same, and may add wheat gluten. Soy sauce goes into dipping sauces, the glaze on grilled fish and chicken, simmered dishes, rice bowls, and the soy‑based sauce brushed on many pieces of sushi.
- Tamari. Often recommended as the gluten‑free alternative, but the same standard defines it as soy sauce made from soybeans, or soybeans with a small amount of wheat. Some tamari is wheat‑free and says so; some is not. A pale shiro soy sauce is the opposite of what it looks like: it is made mostly from wheat.
- Miso. The standard for miso recognizes barley miso, made with barley koji, alongside rice miso and soybean miso. A kitchen may use one, or a blend, without thinking of it as “barley”.
- Batter and breadcrumbs. Tempura batter is wheat flour. Tonkatsu and other fried cutlets are coated in wheat breadcrumbs.
- Fu. Wheat gluten itself, shaped and dried or fresh, served in clear soups, simmered dishes and sweets — especially in Kyoto and in temple cooking.
- Noodles and dumplings. Udon, ramen and gyoza wrappers are wheat. Most soba noodles use wheat as a binder.
- Barley tea. Mugicha, the roasted barley tea that many restaurants pour without asking.
- Curry and sauces. Japanese curry roux and many bottled sauces thicken with wheat flour.
Which Japanese meals are easier, and which are harder?
The rule from the kitchen is the same as for any restriction: the later the seasoning goes on, the easier it is to change. Salt added at the end can replace soy sauce. A broth simmered since morning cannot be changed.
| Format | Where wheat or barley usually is | How it goes |
|---|---|---|
| Sashimi | The soy sauce on the side | Easier — skip it, or bring your own wheat‑free soy sauce if the restaurant agrees |
| Grilled fish or chicken with salt (shioyaki, shio) | Only if a soy glaze is added | Easier — ask for salt only |
| Sushi | Soy‑based sauce brushed on some pieces; sweet sauce on eel; marinated fish | Possible with notice — ask for no sauce on any piece |
| Tempura | The batter; the dipping sauce | Hard — the batter is the dish, and the oil is shared |
| Kaiseki | Soy sauce and miso in many courses; fu; a tempura course | Hard — only with advance notice, and not at every restaurant |
| Soba | Wheat binder in many noodles; soy‑based dipping sauce; shared boiling water | Hard — ask carefully |
| Ramen, udon, gyoza | Wheat noodles and wrappers; soy or miso broth | Hard |
| Yakitori | Soy‑based tare sauce | Possible — ask for salt, and ask whether the grill is shared with sauced skewers |
What actually happens in a restaurant kitchen?
Three things we see in restaurant kitchens, which is why we ask guests to tell us early:
The course is prepared before you arrive. At a set‑course restaurant — sushi omakase, kaiseki — the stocks, sauces and simmered dishes are made in the morning for everyone booked that evening. A request made at the table cannot take the soy sauce out of a dish that is already seasoned. The same request made when you book can: the cook plans a different dish, or sets your portion aside before the seasoning goes in.
The fryer and the pot are shared. Most Japanese restaurants have one fryer and one pot of boiling water. Tempura, katsu and anything else battered go into the same oil. In a soba shop, 100 percent buckwheat noodles are often boiled in the same water as wheat noodles, and sobayu, the cooking water served at the end, comes from that pot. If trace contact matters to you, say so — and expect that many restaurants will answer honestly that they cannot prevent it.
“Gluten” is heard as “wheat flour”. Many cooks will understand gurutein as flour and batter, and not think of soy sauce, miso or barley tea. Name the ingredients, not the word.
Can I ask for tamari, or bring my own soy sauce?
You can ask, and the answer varies. Few restaurants keep a wheat‑free soy sauce, and as above, tamari is not automatically wheat‑free. The more practical route is often to bring a small bottle of wheat‑free soy sauce and ask, when you book, whether you may use it at the table. Some restaurants will agree; some will not, especially where the chef seasons each piece. Ask before the day, not at the counter.
How do I tell a restaurant in Japan?
Tell the restaurant when you book. Japan’s Consumer Affairs Agency notes that allergen labeling for restaurant and takeaway food is not mandatory — it is something each business chooses to do. The labels you may know from packaged food in Japan do not apply to what a restaurant serves you, so the conversation before the meal is what protects you. The agency’s own checklist for restaurants asks them to tell guests about the possibility of cross‑contact, and to leave the final judgment of what to eat to the guest.
Say it as a list of ingredients:
| What to say | Japanese | Romaji |
|---|---|---|
| I have celiac disease and cannot eat any wheat, barley or rye. | セリアック病のため、小麦・大麦・ライ麦は少しでも食べられません。 | Seriakku‑byō no tame, komugi, ōmugi, raimugi wa sukoshi demo taberaremasen. |
| Soy sauce and miso contain wheat too, so please leave them out. | 醤油や味噌にも小麦が入っているので、使わないでいただけますか。 | Shōyu ya miso ni mo komugi ga haitte iru node, tsukawanaide itadakemasu ka. |
| May I bring my own wheat‑free soy sauce? | 小麦を使っていない醤油を持参してもよろしいですか。 | Komugi o tsukatte inai shōyu o jisan shite mo yoroshii desu ka. |
| Is the frying oil shared with tempura? | 揚げ油は天ぷらと同じですか。 | Ageabura wa tenpura to onaji desu ka. |
| Could I have water instead of barley tea? | 麦茶ではなく、お水をいただけますか。 | Mugicha de wa naku, omizu o itadakemasu ka. |
Say these lines when you book, and show the same words in writing when you arrive. We made a free Japanese dining card that spells this out for the kitchen — soy sauce, miso, batter and fu included — for you and everyone at your table.
A few practical notes:
- Give the kitchen a way to say yes. “Could the fish be finished with salt instead of soy sauce?” is easier to agree to than “no gluten”.
- Accept an honest no. A restaurant that says it cannot rule out shared oil is telling you something useful.
- Allow time. Two or three days’ notice gives a set‑course restaurant room to plan.
- Talk to your doctor about how strict you need to be while traveling. This guide describes ingredients and kitchen practice, not medical care.
For the wider picture of how Japanese restaurants handle dietary needs, see our guide to dietary needs at Japanese counters and our phrases for allergies and dietary needs. If you also avoid pork and alcohol, see our guide to halal and Muslim‑friendly dining. For how Japan labels allergens, and why a serious allergy has to be declared when you book, see our food allergy guide.
Before you go
If you want a restaurant to know all of this without a conversation in Japanese, the dining card puts it on one page for the kitchen. When we book for you, we pass this on to the restaurant in Japanese.
Sources
- NHS (UK National Health Service), “Coeliac disease”: definition as an immune reaction to gluten; gluten is found in wheat, barley and rye; a gluten‑free diet is the treatment. Page last reviewed 31 March 2023. https://www.nhs.uk/conditions/coeliac‑disease/
- Ministry of Agriculture, Forestry and Fisheries (農林水産省), Japanese Agricultural Standard for soy sauce (しょうゆの日本農林規格, JAS 1703:2020), clauses 3.8–3.13: koikuchi and usukuchi made from soybeans with roughly equal wheat (usukuchi may add wheat gluten); tamari from soybeans, or soybeans with a small amount of wheat; shiro from a small amount of soybeans with wheat or wheat gluten. The definitions are unchanged from the 2015 text. https://www.maff.go.jp/j/jas/kaigi/attach/pdf/201125‑1.pdf
- Ministry of Agriculture, Forestry and Fisheries, Japanese Agricultural Standard for miso (みそ, JAS 0022:2025), clauses 3.6 and 3.11–3.14: barley miso is made with barley koji, and barley koji is made from barley or naked barley; rice miso and soybean miso are defined alongside it. https://www.maff.go.jp/j/jas/jas_standard/attach/pdf/index‑446.pdf
- Consumer Affairs Agency (消費者庁), report on promoting allergen information in restaurant and takeaway food, February 2023 (令和5年2月): allergen labeling for restaurant and takeaway food is not mandatory and is a voluntary effort by each business. https://www.caa.go.jp/policies/policy/local_cooperation/local_consumer_administration/advancedmodel/2022/assets/consumer_cooperation_cms201_230523_01.pdf
- Consumer Affairs Agency, checklist for restaurant and takeaway businesses providing allergen information: tell guests about possible cross‑contact; the guest decides what they can eat. https://www.caa.go.jp/policies/policy/food_labeling/food_sanitation/allergy/efforts/assets/food_labeling_cms204_240509_05.pdf
This guide describes ingredients and kitchen practice. It is not medical advice; for celiac disease, follow your doctor’s guidance.
