Tamari and soy sauce are nutritionally similar, but tamari has a slight edge in a few areas: more protein per tablespoon, a cleaner ingredient list in most brands, and the option to go gluten-free. The differences are real but modest, and for most people, neither sauce is dramatically healthier than the other.
How Tamari and Soy Sauce Differ
Both are fermented soybean products, but they diverge in one key ingredient: wheat. Standard soy sauce (shoyu) is brewed from a roughly equal mix of soybeans and wheat. Tamari originated as the liquid byproduct of miso fermentation and is traditionally made with little to no wheat. That single difference ripples through the nutritional profile, the flavor, and who can safely use each one.
Because tamari is more soybean-dense, it tends to be thicker, darker, and richer in flavor. This also means you can often use slightly less of it to get the same savory depth, which can matter when you’re watching sodium intake.
Protein and Amino Acids
Tamari delivers roughly 50% to 100% more of most essential amino acids per tablespoon compared to standard soy sauce. A tablespoon of tamari contains about 132 mg of leucine versus 86 mg in soy sauce, and 132 mg of lysine versus 61 mg. Tryptophan, which your body uses to produce serotonin, comes in at 33 mg per tablespoon of tamari compared to 15 mg in soy sauce.
Tamari also contains significantly more glutamic acid (434 mg vs. 253 mg per tablespoon), which is the compound responsible for umami flavor. This is why tamari tastes richer and more complex, and why a little goes further in cooking.
That said, nobody relies on soy sauce as a protein source. The absolute amounts are small either way. The practical takeaway is that tamari packs more flavor-relevant compounds into each serving, which can help you use less overall.
Sodium Content
This is where most people expect tamari to win, but the reality is more nuanced. Standard tamari and standard soy sauce contain similar amounts of sodium per serving, both landing in the range of 900 to 1,000 mg per tablespoon. That’s roughly 40% of the daily recommended limit in a single tablespoon.
Both products come in reduced-sodium versions. “Less sodium” varieties typically contain around 570 mg per tablespoon, while products labeled “low sodium” must contain 140 mg or less per serving. If sodium is your main concern, the label matters far more than whether you pick tamari or soy sauce. Look specifically for “reduced sodium” or “low sodium” on the bottle rather than assuming one type is automatically lower.
Gluten-Free Considerations
For anyone with celiac disease or gluten sensitivity, tamari is the clear winner. Many tamari products are certified gluten-free, while standard soy sauce always contains wheat as a core ingredient.
One important caveat: not all tamari is gluten-free. Some brands include small amounts of wheat in their formula, and even wheat-free tamari may be produced in facilities that also process wheat. If you have celiac disease, look for certification from a recognized gluten-free organization rather than relying on the word “tamari” alone. Cross-contamination is a real risk with products made in shared facilities.
Additives and Processing
This is an underappreciated difference between the two. Many mass-market soy sauces, especially cheaper brands, contain additives that tamari typically does not. Caramel color is one of the most common, used to darken the sauce and create a uniform appearance. It’s one of the most widely consumed food colorings in the world, showing up in everything from cola to gravy. Some conventional soy sauces also include preservatives like sodium benzoate, corn syrup, or added sugar.
Tamari brands tend to have shorter, simpler ingredient lists: soybeans, water, salt, and sometimes a small amount of alcohol as a natural preservative. This isn’t universal, so reading labels still matters, but as a category, tamari leans toward fewer processed ingredients.
The cheapest soy sauces on the market skip fermentation entirely, using a chemical process called acid hydrolysis to break down soybeans in days rather than months. These products lack the complex flavor compounds that develop during natural fermentation and often compensate with additives. Tamari, by contrast, is almost always naturally fermented.
Histamine Levels
If you have histamine intolerance, this is something to pay attention to. A study measuring histamine in fermented condiments found dramatically high levels in tamari: 2,392 micrograms per gram of sample. One brand of standard soy sauce came in at 220 micrograms per gram, roughly ten times lower. For context, blue cheese, a food widely known to trigger histamine reactions, measured at 864 micrograms per gram.
Tamari’s higher histamine content likely reflects its soybean-dense composition and fermentation process. If you experience headaches, flushing, digestive distress, or nasal congestion after eating fermented foods, tamari could be a worse choice than standard soy sauce, not a better one. This is one area where tamari’s “healthier” reputation doesn’t hold up for a specific subset of people.
Isoflavones and Phytoestrogens
Both tamari and soy sauce contain isoflavones, the plant compounds in soy that weakly mimic estrogen. Standard soy sauce made from soy and wheat contains about 0.78 mg of daidzein and 0.39 mg of genistein per 100 grams, according to USDA data. These are very low concentrations compared to whole soy foods like tofu or edamame.
The USDA hasn’t published separate isoflavone data for tamari, but given its higher soybean concentration, levels are likely somewhat higher. In practical terms, neither sauce delivers enough isoflavones to have any meaningful hormonal effect at normal serving sizes. If you’re concerned about phytoestrogens, the tablespoon of sauce on your stir-fry is not the soy product to worry about.
Which One Should You Use
Tamari is the better choice if you need to avoid gluten, prefer a cleaner ingredient list, or want a richer umami flavor from a smaller amount. It delivers more protein and amino acids per serving, though the absolute quantities are too small to matter nutritionally on their own.
Standard soy sauce is the better choice if you have histamine intolerance, since tamari can contain dramatically more histamine. It’s also more widely available and usually cheaper.
For everyone else, the differences are marginal enough that the biggest health variable isn’t which one you choose but how much you use. Both are high-sodium condiments, and keeping portions to a teaspoon or switching to a reduced-sodium version will do more for your health than swapping one for the other.