Hidden gluten in Japanese food is something many travelers don’t expect. While Japanese cuisine looks naturally gluten free with rice, fish, and vegetables, popular seasonings like soy sauce, dashi, and miso often contain hidden wheat. In this article, we explain where gluten hides, why it matters, and how to eat safely in Japan.
What is hidden gluten in Japanese food?
Gluten is a protein found in wheat, barley, and rye. In Japan, even foods that don’t look like bread or noodles may contain wheat as a hidden ingredient. This is especially true for seasonings:
- Soy sauce (しょうゆ) — traditionally brewed with wheat
- Dashi (だし) — soup stock that sometimes uses wheat-based soy sauce or flavorings
- Miso (みそ) — some types are blended with wheat
For people with celiac disease or gluten sensitivity, these hidden sources can trigger reactions.
Hidden gluten in soy sauce
Why soy sauce often contains wheat
Most Japanese soy sauce (shoyu) is brewed with both soybeans and wheat. The wheat is fermented together with soy, giving the sauce its mild sweetness and aroma.
According to the Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF), over 80% of soy sauce produced in Japan uses wheat as part of its recipe.
👉 出典：農林水産省｜しょうゆと大豆
Gluten free alternatives for soy sauce
- Tamari (たまり醤油): traditionally made with little or no wheat. Check labels, as some modern tamari still includes wheat.
- Certified gluten free soy sauce: available in international supermarkets or health food stores in Japan.
Hidden gluten in dashi (Japanese soup stock)
Common ingredients with gluten
Dashi is a soup stock made from kombu seaweed, bonito flakes, dried sardines, or shiitake mushrooms. While these are gluten free, many instant dashi powders add soy sauce or seasoning that contains wheat.
Safer gluten free dashi options
- Homemade dashi from kombu and bonito is usually safe.
- Look for packs labeled 「グルテンフリー」 or 「小麦不使用」 in Japanese supermarkets.
Hidden gluten in miso
Types of miso and wheat content
Miso is a fermented paste made from soybeans, salt, and koji (rice or barley). However, some miso varieties include 麦 (barley) or 小麦 (wheat) in the fermentation process.
- Kome miso (米みそ): made from rice koji, usually gluten free.
- Mugi miso (麦みそ): contains barley, not safe for gluten free.
- Awase miso (合わせみそ): blended miso, sometimes includes wheat or barley.
Gluten free miso options
Choose rice miso (米みそ) and always check the ingredient label for 「小麦」 (wheat) or 「大麦」 (barley). Many Japanese supermarkets now label allergy ingredients clearly.
Why hidden gluten matters for celiac and gluten intolerance
For people with celiac disease, even trace amounts of gluten can cause serious reactions:
- Digestive problems
- Fatigue and nutrient malabsorption
- Long-term intestinal damage
Even those with non-celiac gluten sensitivity may experience discomfort, so being aware of hidden gluten is essential.
Tips to avoid hidden gluten in Japan
How to ask in restaurants and shops
When eating out, ask staff if food contains wheat or soy sauce with gluten.
Useful Japanese phrases
- グルテンを含まない食品はありますか？
(Guruten o fukumanai shokuhin wa arimasu ka?)
“Do you have food without gluten?” - 醤油に小麦が入っていますか？
(Shouyu ni komugi ga haitte imasu ka?)
“Does the soy sauce contain wheat?” - みそに小麦や大麦は入っていますか？
(Miso ni komugi ya oomugi wa haitte imasu ka?)
“Does the miso contain wheat or barley?”
Summary: eating safely with hidden gluten risks
- Many Japanese seasonings contain hidden gluten: soy sauce, miso, and instant dashi.
- Always check for 「小麦」 (wheat) or 「大麦」 (barley) on labels.
- Choose tamari or certified gluten free soy sauce, and rice miso (米みそ).
- When eating out, use simple Japanese phrases or carry a translation card.
With awareness and preparation, you can still enjoy Japanese cuisine safely while avoiding hidden gluten.
