One level tablespoon of tamari, about 18 grams, carries roughly 1000 milligrams of sodium, the equivalent of 2.5 grams of salt. The same spoon of miso paste carries about 670 milligrams, or 1.7 grams of salt. The World Health Organization recommends staying under 2000 milligrams of sodium a day. A single spoon of tamari therefore uses up half the day.

That is the first thing worth knowing about these two products, and it is the thing almost nobody writes down. They are usually sold as sources of protein, minerals and probiotics. At the dose you actually use, a spoon here and there, none of those arguments carry weight: the same spoon of miso gives you 2.3 grams of protein and under half a milligram of zinc. They are seasonings, and they should be judged as seasonings.

What makes miso and tamari genuinely useful is neither their composition nor their folklore. It is that they let you salt less while giving the impression of the opposite, and that they do something no spice can do.

Umami is a specific mechanism, not an atmosphere

Umami was internationally recognised as the fifth basic taste on the back of psychophysical, electrophysiological and biochemical work carried out largely in Japan. Three substances trigger it: glutamate, inosinate and guanylate. Three receptors have been identified in humans, T1R1+T1R3, mGluR4 and mGluR1, and only one of them, T1R1+T1R3, shows the effect that matters in a kitchen.

That effect is synergy. According to the review published in BioMed Research International in 2015, the human response to a mixture of glutamate and inosinate is about eight times the response to glutamate alone, against roughly 1.7 times in rats. Put plainly: doubling the miso does not double the umami, but adding a source of nucleotides to that miso multiplies it.

This is the only genuinely actionable point in the whole chapter. Miso and tamari supply free glutamate. Dried mushrooms, shiitake in particular, supply nucleotides. Seaweeds such as kombu supply glutamate. A broth of dried shiitake finished with miso does not taste like the sum of its parts, it tastes like something else entirely. That is the whole principle behind a plant-based dashi, and the guide to edible mushrooms opens the same trick up beyond shiitake.

The European Food Safety Authority also points out that glutamic acid is an ordinary amino acid, produced naturally by the human body and present in free form in tomatoes, soy sauce and certain cheeses. The glutamate in a miso and the glutamate in an industrial flavour enhancer are the same molecule. The difference lies elsewhere: in the matrix, in the hundreds of other compounds fermentation produces, and in the quantity.

What miso and tamari actually are

Miso is a paste made by fermenting soya beans with salt and koji. Koji is a grain, usually rice or barley, on which a mould called Aspergillus oryzae has been grown. That mould produces enzymes which cut the soya proteins into free amino acids, glutamate among them. This proteolysis is what creates the flavour, not the passage of time on its own.

A metagenomic study published in Frontiers in Microbiology in 2026 sequenced four Japanese misos and confirmed that Aspergillus oryzae does indeed dominate koji-based misos. The same work describes an unusual case, nesashi miso, fermented spontaneously without any koji starter: it is dominated instead by other filamentous fungi, mainly Mucor and Penicillium, and it clusters with spontaneous Chinese fermentations rather than with conventional misos. Two useful things follow. The first is that miso is not a standardised product. The second is that if you take on homemade chickpea miso, you start from a koji, not from a jar left to chance.

Tamari, historically, is the liquid that drains off a vat of miso. It is a soy sauce made with little or no wheat, whereas shoyu, the everyday Japanese soy sauce, combines comparable proportions of soya and roasted wheat. This is not a difference in quality, it is a difference in starting composition, and it has real consequences for gluten and for flavour.

Miso varieties read mostly through colour, which reflects fermentation time and the proportion of grain. A pale shiro miso holds more rice, ferments for less time and stays mild. A red aka miso holds more soya, ferments longer and turns frankly salty and assertive. A mugi miso is made with barley. The choice is not cosmetic: a shiro miso dissolves into a dressing without taking it over, while an aka miso will flatten everything around it if you do not measure.

The only table that really matters

The figures below come from the USDA FoodData Central database, SR Legacy series, per 100 grams of product. Salt equivalent is sodium multiplied by 2.5, the formula written into annex 1 of the Swiss ordinance on food information.

Product	Sodium per 100 g	Salt equivalent per 100 g	Protein per 100 g
Miso	3728 mg	9.3 g	12.8 g
Tamari	5586 mg	14.0 g	10.5 g
Shoyu (soya and wheat)	5493 mg	13.7 g	8.1 g
Reduced-salt shoyu	3598 mg	9.0 g	9.1 g

Scaled to real quantities, that works out as follows. A teaspoon of miso, about 6 grams, carries 224 milligrams of sodium, or 0.56 grams of salt. A tablespoon, about 18 grams, carries 671 milligrams, or 1.68 grams of salt. A teaspoon of tamari carries 335 milligrams of sodium, 0.84 grams of salt, and a tablespoon 1005 milligrams, 2.51 grams of salt.

The official reference points make those numbers legible. WHO recommends under 2000 milligrams of sodium a day for adults, under 5 grams of salt, and notes that the global mean intake reached 4278 milligrams a day in 2021, more than double. It associates 1.7 million deaths with excess sodium for 2023 alone. The NHS sets the ceiling at 6 grams of salt a day from age 11, 5 grams from 7 to 10, 3 grams from 4 to 6, 2 grams from 1 to 3, and names soy sauce explicitly among the sauces to go easy on.

Three practical consequences. Reduced-salt shoyu carries roughly 35 per cent less sodium than standard shoyu, which makes it, on this criterion alone, the best buy on the shelf. Weight for weight, tamari is saltier than miso, which runs against the intuition that the paste must be the more concentrated product. And if you are following a salt-free cooking plan, these two are not tolerated exceptions: they are your biggest single items.

Measuring: by the litre, not by eye

For a soup, count 60 to 80 grams of miso per litre of broth. At 70 grams that is 2610 milligrams of sodium for the whole pan, roughly 6.5 grams of salt spread over five 200 millilitre bowls, so 1.3 grams of salt per bowl. That is reasonable for a dish that is the main seasoning of the meal, provided you do not salt anywhere else.

For a dressing, one level teaspoon of shiro miso for two people completely changes a sauce, and it replaces the salt rather than joining it. For a tofu marinade, count a teaspoon of miso and a teaspoon of tamari per 250 grams of tofu, which stays under 1.4 grams of salt for two portions. The detailed marinade techniques are worth reading before you double anything out of habit.

For glazing roast vegetables, a teaspoon of miso slackened in a tablespoon of oil covers a 700 gram tray comfortably. Miso browns fast: brush it on for the last twenty minutes, not at the start.

The rule that covers all of this: taste before you salt, never the other way round. Once the miso is in, the background salinity is already there, and the pinch you add out of habit is the one that tips the dish over.

What the research says about miso and blood pressure, without stretching it

This point deserves care, because it circulates widely in a flattened version.

A Japanese prospective cohort published in the BMJ in 2020, covering 92,915 people aged 45 to 74 followed for a mean 14.8 years with 13,303 deaths, found no association between total soy intake and all-cause mortality, with hazard ratios of 0.98 in both men and women. It did find an inverse association for fermented soy, natto and miso, with hazard ratios of 0.90 in men and 0.89 in women. The authors themselves state that the finding should be read cautiously, because the association may be attenuated by unadjusted residual confounding.

Another analysis from the same large Japanese study, in the Journal of Nutrition in 2017, followed 926 men and 3239 women with normal blood pressure for five years. The highest tertile of fermented soy intake was associated with a lower risk of developing high blood pressure, odds ratio 0.72. Total soy and tofu showed no association.

A randomised trial in Hypertension Research in 2019 compared, in 40 people aged 40 to 69 with high-normal blood pressure or stage I hypertension, 32 grams of miso supplying 3.8 grams of salt a day against a control soy food supplying 0.2 grams. After eight weeks daytime pressure was unchanged and night-time pressure had fallen significantly in the miso group.

What can be honestly drawn from this? That the salt in miso may not behave exactly like table salt at equal quantity, and that there is a serious line of enquiry pointing that way. What cannot be drawn from it: that miso lowers blood pressure. The trial covers forty people over eight weeks with two commercial misos selected for specific properties, in a Japanese population whose baseline sodium intake is far above ours. The cohorts are observational. If you have hypertension, the plan is the one your doctor sets, and the miso argument does not buy back an excess of salt.

What is solid is the reverse lever. A crossover trial published in Frontiers in Nutrition in 2024 followed 42 people in Vietnam given the same salt-reduction guidance: the group allowed to keep its glutamate-rich seasonings cut sodium excretion by 46 per cent over six weeks, against 22 per cent in the group whose seasonings were restricted. The sample is small and the food context is a long way from ours, but the logic fits what a 2024 review in Food Research International describes about using umami substances to cut salt. Umami does not compensate for salt, it lets you use less without the dish collapsing. That is exactly the ground covered in our piece on seasoning without salt using herbs, spices and citrus.

Gluten: what Swiss law says, and what the laboratory says

Tamari is routinely presented as the soy sauce for people who cannot tolerate gluten. That is true in practice in many cases, and false as a general rule.

The Swiss federal ordinance on food information sets the thresholds in its article 41. A food may carry the claim “gluten-free” if its gluten content does not exceed 20 milligrams per kilogram at the point of sale, and “very low gluten” up to 100 milligrams per kilogram. Annex 2 further requires that gluten-containing cereals always appear on the label when used as an ingredient. So: if a tamari contains wheat, the label has to say so, and only the “gluten-free” claim carries legal weight.

The analytical data complicate the picture rather than simplifying it. A study in the Journal of Food Protection in 2017 tracked soy sauce fermentation using ELISA, lateral flow devices and Western blot: gluten was no longer detected after the moromi stage, nor in commercial soy, teriyaki and Worcestershire sauces. An LC-MS analysis published in Food Chemistry in 2018 reached the same conclusion, detecting no gluten in the soy sauces examined even though wheat was a declared ingredient, indicating extensive hydrolysis during production. Both sets of authors add the same caveat: whether every immunopathogenic element of gluten is genuinely hydrolysed remains to be established.

The sensible course follows directly. With coeliac disease, buy only products carrying the explicit “gluten-free” claim, and treat a tamari without that claim as an untested product rather than a safe one. Wheat being hydrolysed during fermentation is an interesting laboratory observation, not a permission.

The points the guides never mention

Biogenic amines. Miso and soy sauce are salted fermented foods, and that kind of matrix can accumulate histamine. Work published in Applied and Environmental Microbiology in 2023 identified Tetragenococcus halophilus as the organism responsible for histamine production during soy sauce fermentation, and showed that shifting the ratio between its producing and non-producing subgroups cut histamine by 34 per cent. A survey published in Food Chemistry in 2007 on forty misos sold in Taiwan found three samples above the 5 milligrams per 100 grams limit the US FDA applies to other products, with a maximum of 22.1. For the vast majority of people this has no consequences at all. For someone on an MAOI or with documented histamine intolerance, it is information missing from more or less every article on miso. Conversely, a 2017 paper isolated Lactobacillus plantarum strains from miso capable of degrading histamine, which shows how strongly the level depends on the individual product.

Iodine. If you replace part of your table salt with miso and tamari, you are replacing salt that is probably iodised with products that are not. It is a quiet side effect of a good intention, and it concerns anyone on a vegetarian or vegan diet directly. Our piece on balancing iodine with seaweed and iodised salt works through it.

Added glutamate. In July 2017 EFSA established a group acceptable daily intake of 30 milligrams per kilogram of body weight per day for glutamic acid and glutamates used as additives, E 620 to E 625. In the same opinion it concluded that estimated dietary exposure may exceed not only that level but also the doses associated in humans with effects such as headache, raised blood pressure and increased insulin, for some population groups. That ADI covers glutamates added as additives, not glutamate naturally present in a fermented food. But if you stack industrial sauces, stock cubes and condiments, the question of total exposure is real, and it stands quite apart from the “natural versus chemical glutamate” argument, which has no molecular basis.

The environmental argument almost always aims at the wrong target

The usual reasoning runs: soya drives deforestation, therefore choose an organic miso and a committed brand. The first half is true, the second does not follow.

According to the data compiled by Our World in Data, more than three-quarters of the world’s soya, 77 per cent, is fed to livestock. Only 7 per cent goes directly to human food as tofu, soy drink, edamame or tempeh. The rest goes into biofuels, industry and vegetable oil. On tropical deforestation itself, cattle ranching accounts for 41 per cent and oilseeds as a whole for 18 per cent.

The Brazilian soy moratorium signed in 2006 illustrates both what works and what leaks: in the two years before the agreement, 30 per cent of soy expansion in the Amazon region came at the expense of forest, against 1 per cent by 2014. But part of that deforestation shifted south into the Cerrado.

The honest conclusion for a jar of miso: at the scale you use it, a few dozen grams a week, the effect of your brand choice on tropical forest is undetectable. The real lever sits on the animal feed side of demand. That does not make the product choice irrelevant, there are good reasons to prefer a cleanly made miso, but those reasons are about flavour and craft, not climate. We have gone through the misunderstandings around soya in misconceptions about soy.

Six mistakes that come up constantly

Boiling the miso “to cook it”. The standard argument invokes preserving probiotics. That argument does not hold: no strain identified in miso carries an authorised health claim, and nothing supports the idea that a spoon of paste in a bowl of soup exerts a documented effect on gut flora. The real reason is more mundane. Miso is a paste that separates and turns grainy in a hard-boiling liquid, and the aroma compounds built during fermentation are volatile. Slacken it in a ladle of broth taken off the heat, then stir it back in.

Salting before tasting. This is the costliest mistake, and it is mechanical: you salt at the end out of habit, when the miso has already done the work.

Treating tamari as liquid salt without counting. One tablespoon is half the WHO daily recommendation. Two swirls of the bottle over a wok is easily three spoons.

Buying miso for the protein. At 12.8 grams per 100 grams, a tablespoon gives you 2.3 grams of protein. It is a seasoning, not a protein food, and that subject belongs in the plant protein guide.

Assuming tamari means gluten-free. Only the legal “gluten-free” claim commits the manufacturer, and it corresponds to a threshold of 20 milligrams per kilogram.

Doubling the dose instead of adding nucleotides. If your broth lacks depth, a second spoon of miso mostly adds salt. A rehydrated dried shiitake, soaking water included, adds the synergy, and the result is not comparable. That is the principle behind homemade umami-rich broths and concentrated broth ice cubes.

Buying and storing in Switzerland

You will find miso and tamari in organic shops, Asian grocers and larger supermarkets, at widely varying prices. Three criteria genuinely matter.

The ingredient list first. A decent miso contains soya, rice or barley, salt, koji and possibly alcohol as a preservative. A longer list signals a reformulated product. For tamari, look for the “gluten-free” claim if that is your criterion, and for the sodium content per 100 grams in the nutrition declaration, which is mandatory.

Colour next, because it tells you what the jar is for. Pale for dressings, creamy sauces and anything where the miso should not announce itself. Dark for root vegetable soups, glazes and slow-cooked dishes.

Storage last. Miso is heavily salted and keeps for several months in the fridge once opened, in a well-sealed container. The surface darkens in contact with air through oxidation, which is a colour change rather than a sign of spoilage. Tamari also keeps better refrigerated once opened, to protect its aroma. Neither freezes usefully.

One label detail is worth knowing in the Swiss and European context: the nutrition declaration states salt, not sodium, so you can read the salt content per 100 grams straight off the jar and compare it with the table above without converting anything. A tamari showing under 12 grams of salt per 100 grams is a reduced-salt product, whether or not anything on the front of the bottle says so.

The ingredient list also separates brewed sauces from the rest. A brewed soy sauce contains soya beans, wheat, water and salt, and nothing else. If you see hydrolysed vegetable protein, caramel colour or glucose syrup, you are holding a chemically produced or blended sauce, which is precisely the kind that skips the fermentation step the umami comes from. That is not a safety issue, it is a question of what you are paying for: the whole point of these two products is the proteolysis carried out by the koji, and a sauce that shortcuts it delivers salt with colour.

Adapting to different profiles

People with hypertension or on a low-sodium diet: miso and tamari are items to count, not to eliminate. A teaspoon of miso at 0.56 grams of salt, replacing cooking salt, fits perfectly well into a low-sodium plan. A tablespoon of tamari at the end of cooking does not.

People with coeliac disease: the “gluten-free” claim is mandatory, without exception. The data showing gluten is no longer detectable after fermentation changes nothing about that rule.

People on MAOIs or with documented histamine intolerance: salted fermented foods are among the matrices concerned, and levels vary sharply between products. That is a question for whoever manages the treatment, not for an article.

Children: the NHS salt ceilings are low, 3 grams a day from 4 to 6 and 2 grams from 1 to 3. A miso soup at 1.3 grams of salt a bowl uses up a serious share of a five-year-old’s day. Dilute further and serve smaller bowls.

Limits of the available data

The USDA values are American reference averages. Artisanal Japanese misos and premium tamari sold in Switzerland can depart from them noticeably in either direction: the label on the product in your hand governs, not this table.

The miso and blood pressure data come almost entirely from Japanese populations whose salt intake and diet differ substantially from the Swiss context. Transposing them therefore remains uncertain.

Finally, no solid data quantify what the “unpasteurised” label actually delivers to the consumer. The claims commonly made about it are unsupported.

Frequently asked questions

Is miso better for you than salt? At equal sodium, the Japanese data suggest miso salt does not behave exactly like table salt, but they do not license that claim outside their context. The one clearly identified benefit is indirect: umami makes you salt less.

Can miso replace tamari? For salinity and depth, yes, by slackening a teaspoon of miso in a little hot water. For the texture of a liquid sauce, no.

Must you really never boil miso? There is no risk involved, only a loss of quality: the paste separates and the volatile compounds go. It is not a safety rule.

Is shoyu inferior to tamari? No. It is slightly less salty than tamari in the USDA data, and its roasted wheat fraction gives it different notes. The choice is about taste and gluten, not quality.

Is miso suitable for children? Yes, within the salt ceiling for their age and diluted considerably more than for an adult.

Is unpasteurised miso more useful? No published data demonstrate that for culinary purposes. It does often have a livelier aroma profile.

How long does an opened jar keep? Several months in the fridge, well sealed. Surface browning is oxidation.

Sources

• World Health Organization, Sodium reduction, updated 11 May 2026.
• NHS, Salt in your diet.
• EFSA, re-evaluation of glutamates added to food, 12 July 2017.
• USDA FoodData Central, SR Legacy: miso 172442, tamari 174278, shoyu 174277, reduced-salt shoyu 172473.
• Swiss ordinance on food information, SR 817.022.16, art. 41 and annexes 1 and 2.
• Our World in Data, Soy.
• Katagiri et al., Association of soy and fermented soy product intake with total and cause specific mortality, BMJ, 2020.
• Ito, Review of the health benefits of habitual consumption of miso soup, Environmental Health and Preventive Medicine, 2020.
• Kondo et al., Long-term intake of miso soup decreases nighttime blood pressure, Hypertension Research, 2019.
• Nozue et al., Fermented soy product intake is inversely associated with the development of high blood pressure, Journal of Nutrition, 2017.
• Li et al., Using LC-MS to examine the fermented food products vinegar and soy sauce for the presence of gluten, Food Chemistry, 2018.
• Cao et al., Detection of gluten during the fermentation process to produce soy sauce, Journal of Food Protection, 2017.
• Kurihara, Umami the fifth basic taste: history of studies on receptor mechanisms and role as a food flavor, BioMed Research International, 2015.
• Hien et al., Dietary free L-glutamate contributes to maintaining a low sodium intake, Frontiers in Nutrition, 2024.
• Ma et al., Ratio of histamine-producing subgroups of Tetragenococcus halophilus, Applied and Environmental Microbiology, 2023.
• Kung et al., Histamine and other biogenic amines and histamine-forming bacteria in miso products, Food Chemistry, 2007.
• Kothe et al., Miso without koji: nesashi miso ecology, Frontiers in Microbiology, 2026.