Is Soy Sauce Low FODMAP? A Surprisingly Clear Yes

Michael Eisenwasser 6 min read

Most soy-related ingredients on the low-FODMAP diet come with an asterisk. Whole soybeans are high FODMAP. Soy milk made from whole beans is high FODMAP, while soy milk made from soy protein is low FODMAP. Firm tofu is generally low FODMAP at typical serves, but silken tofu has a much smaller low-FODMAP serving size because pressing doesn't remove as many of the oligosaccharides. It's confusing.

Soy sauce is one of the rare exceptions. It's a clean yes. That's worth knowing if you're trying to cook food that tastes like food on the elimination phase.

The short answer

Regular soy sauce is low FODMAP at 2 tablespoons per serving, per Monash testing. Tamari (the wheat-free version) is also low FODMAP at 2 tablespoons. Coconut aminos are low FODMAP at 1 teaspoon.

The catch isn't the soy sauce itself. It's the sauces that contain soy sauce plus other things: teriyaki, hoisin, oyster sauce, most stir-fry sauces in a jar. Those almost always carry added garlic and onion, which moves the whole bottle into high-FODMAP territory regardless of what the soy sauce is doing.

Why soy sauce is low FODMAP

Whole soybeans are loaded with galacto-oligosaccharides (GOS) and fructans, both of which your small intestine can't break down. That's why a handful of edamame or a scoop of soy flour can set off symptoms fast.

Soy sauce is different because it's not whole soybeans. It's what's left after months of fermentation plus pressing and filtration.

Traditional soy sauce is made by inoculating soybeans (usually with wheat) with Aspergillus mold, salting heavily, and letting the mash ferment for months. Fermentation and the subsequent pressing reduce the fermentable carbohydrates that started in the beans. What ends up in the bottle is mostly water, salt, amino acids, and flavor compounds. The details vary by process, but the tested outcome is what matters.

That tested outcome: Monash's lab work puts regular soy sauce at a low-FODMAP serve of 2 tablespoons (about 30 ml), which is more than most recipes call for. FODMAP Friendly, the other main certifying body, found no detectable FODMAPs at typical serves and allows freely in reasonable amounts.

Tamari

Tamari is traditional Japanese soy sauce made with little or no wheat. It's low FODMAP at the same 2-tablespoon serve as regular soy sauce.

For readers who are also gluten-free (whether from celiac disease, non-celiac gluten sensitivity, or the fructan overlap with wheat), tamari is the default swap. Certified gluten-free tamari is easy to find at most US grocery stores. San-J's organic reduced-sodium tamari is certified low FODMAP by FODMAP Friendly and is widely recommended in the FODMAP community.

Taste-wise, tamari is slightly richer and less sharp than regular soy sauce. It works anywhere you'd use soy sauce, though some people prefer it for dipping and regular soy sauce for cooking. That's a preference call, not a FODMAP call.

Coconut aminos

Coconut aminos get a lot of airtime in the gluten-free and Paleo worlds. They're made from coconut sap, salt, and fermentation, and they taste close to a sweeter, milder soy sauce.

Coconut aminos have been tested by Monash and FODMAP Friendly, and the tested low-FODMAP serve is substantially smaller than soy sauce's 2 tablespoons, think teaspoons, not tablespoons, and brand-dependent. At larger serves the fructan load from the coconut sap can push coconut aminos into moderate or high FODMAP territory, so check the current Monash app entry for the brand you're buying.

So if you're specifically trying to avoid soy or gluten and you want a substitute, coconut aminos work, but you have to watch the quantity in a way you don't with soy sauce or tamari. Practically speaking, that usually means using coconut aminos as a finishing drizzle or splash rather than pouring it freely into a stir-fry.

Where this breaks down: the "soy sauce plus" sauces

Here's where people get tripped up. Most composed Asian sauces in a jar start with soy sauce and then add the things that make them taste like those sauces.

Teriyaki sauce. Most supermarket bottles include garlic and/or onion powder. The soy sauce is fine, the garlic isn't. Monash's own homemade teriyaki recipe skips the garlic and uses alternatives; Fody makes a low-FODMAP-certified "No Soy" teriyaki for the US market. Bottled teriyaki sauce from a regular grocery brand is generally not safe on elimination.

Hoisin sauce. Often contains garlic, and the base frequently includes fermented soybean paste plus sweeteners that can stack FODMAPs fast. Skip the generic bottles. Low-FODMAP-certified versions exist but aren't the default on most grocery shelves.

Oyster sauce. Varies brand to brand. Many include garlic and onion. A few don't. If you can't read the label easily or can't find a certified brand, assume it's out during elimination.

Stir-fry sauces, dumpling sauces, general "Asian" marinades. Same rule: the soy sauce is the innocent part, the garlic and onion further down the ingredient list are the problem. Read every label.

Sweet soy sauce (kecap manis). A separate category: Monash lists this low FODMAP at 1 tablespoon, half the regular soy sauce serve. Fine in small splashes, not something to pour.

The practical rule: a bottle that says "soy sauce" and has a short ingredient list (soybeans, wheat or not, salt, water, maybe a preservative) is safe at 2 tablespoons. A bottle that says anything else on the front is a label check.

A note for readers who also have histamine intolerance

This is where the low-FODMAP diet and the low-histamine diet part ways hard.

I've written extensively about soy sauce on the sister site. Soy sauce is high in histamine because fermentation, the same process that strips out the FODMAPs, lets histamine accumulate over months of aging. Tamari can actually test higher in histamine than regular soy sauce because it's often aged longer. If histamine intolerance is part of your picture, coconut aminos are usually the better move despite the tighter FODMAP serving size.

If you're not sure whether you're dealing with IBS, SIBO, or histamine intolerance, this post walks through the differences.

What this looks like in practice

For most people on the low-FODMAP diet without a histamine issue, soy sauce is one of the easiest wins. It's in a familiar form, it's cheap, it's at every grocery store, and the 2-tablespoon serve is generous enough for normal cooking.

A weeknight stir-fry pattern that works: garlic-infused oil in the pan, ginger and scallion greens for aromatics, your protein and low-FODMAP vegetables, a splash of tamari or regular soy sauce at the end. Skip the jarred stir-fry sauce, which is where the hidden garlic and onion usually live. The result tastes like actual food, not diet food.

If you're newer to all this, this explainer on what FODMAPs actually are covers the groundwork.

The shorter version: buy the plain bottle, skip the composite sauces, keep serves in the 1-to-2-tablespoon range, and you have one ingredient on the low-FODMAP diet that doesn't need a workaround.

Track your symptoms and discover patterns with FODMAP Tracker. Includes a database of 1,000+ foods with FODMAP ratings.