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Miso is a salty, savory paste made by fermenting soybeans with salt and koji, a grain or soybean base cultured with the mold Aspergillus oryzae. A tablespoon adds deep flavor for about 34 calories, but it also carries about 28% of the Daily Value for sodium, according to USDA data, which is the number that matters most for most people. Below are the USDA miso nutrition facts, how miso compares with soy sauce and salt, white miso vs red miso, what happens to its microbes in miso soup, and who should check with a clinician first.
Peptide Labs does not sell miso or miso products. This article is general nutrition information, not medical advice.
Key Takeaways
- Miso is fermented soybean paste made with salt and koji; rice, barley and soybean versions exist.
- One tablespoon has about 34 calories, 2 grams of protein and 28% of the Daily Value for sodium.
- Tablespoon for tablespoon, miso has less sodium than regular soy sauce but more than reduced-sodium soy sauce.
- Lighter miso is usually aged for a shorter time; darker miso is aged longer and tastes stronger.
- Soy allergy, sodium limits, barley-based miso for people avoiding gluten and MAOI medicines are the main cautions.
What is miso paste?
A 2021 review of traditional miso making in the Journal of Fungi defines miso as a semisolid paste made mainly from soybeans that are fermented and matured with salt and with soybeans or grains cultured with koji mold. The main koji mold is Aspergillus oryzae, the same group of molds used to start soy sauce. Salt-tolerant yeasts and lactic acid bacteria join in during fermentation, and the paste then matures for anywhere from about a month to several years.
Japanese labeling standards sort miso paste by its koji base:
- Rice miso: koji grown on rice. The review reports it makes up about 80% of miso produced in Japan.
- Barley miso: made the same way with barley instead of rice, mostly in southern Japan.
- Soybean miso: koji grown on the soybeans themselves, usually matured for many months.
- Mixed miso: blends of the above.
Miso sits alongside tempeh and natto as one of the traditional soybean foods made by fermentation. Unlike those two, it is used as a seasoning rather than eaten as a main protein, which shapes how its nutrition should be read.
Miso nutrition per tablespoon
The table uses the USDA FoodData Central SR Legacy entry for miso (FDC 172442) at the USDA serving of 1 tablespoon (17 grams), with percent Daily Value (%DV) based on the FDA Daily Values printed on Nutrition Facts labels. Brands vary, so the label on your tub is the final word.
| Nutrient (miso) | Per 1 tbsp (17 g) | % Daily Value |
|---|---|---|
| Calories | 34 | Not applicable |
| Protein | 2.2 g | 4% |
| Total fat | 1.0 g | 1% |
| Carbohydrate | 4.3 g | 2% |
| Fiber | 0.9 g | 3% |
| Sugars | 1.1 g | Not set |
| Sodium | 634 milligrams | 28% |
| Copper | 0.07 milligrams | 8% |
| Manganese | 0.15 milligrams | 6% |
| Zinc | 0.4 milligrams | 4% |
| Vitamin K | 5.0 micrograms | 4% |
| Potassium | 36 milligrams | 1% |
Per 100 grams the USDA entry looks more impressive, with about 13 grams of protein and 5 grams of fiber, but nobody eats miso by the bowlful. At a seasoning-sized spoonful, miso contributes small amounts of protein, fiber, copper and manganese and a large amount of sodium. If you want a soy food for protein, edamame, tempeh and natto deliver far more per serving; our protein foods guide compares other options.
Miso and sodium: how it compares
The FDA Daily Value for sodium is less than 2,300 milligrams a day, and the FDA describes 20% DV or more in a serving as high. A tablespoon of miso crosses that line on its own. Here is how it compares with other salty seasonings in USDA data.
| Seasoning (FDC ID) | Serving | Sodium (mg) | % Daily Value |
|---|---|---|---|
| Miso (172442) | 1 tbsp (17 g) | 634 | 28% |
| Soy sauce, shoyu (174277) | 1 tbsp (16 g) | 879 | 38% |
| Soy sauce, shoyu, low sodium (172473) | 1 tbsp (14 g) | 511 | 22% |
| Table salt (173468) | 1 tsp (6 g) | 2,325 | 101% |
So miso is a concentrated salt source, though spoon for spoon it carries less sodium than regular soy sauce. The Journal of Fungi review notes that the salt content of miso ranges from about 5% to 13%, typically 11% to 13%, so two brands can differ meaningfully. Some products are sold as reduced-salt miso; the Nutrition Facts panel shows how much sodium a serving actually contains. Our low sodium guide explains the FDA label terms, and our salt comparison covers why specialty salts do not change the sodium picture much.
White miso vs red miso
Color is the quickest way shoppers tell miso apart, and it mostly reflects how the paste was made and how long it aged. The Journal of Fungi review explains that the Maillard reaction, the same browning reaction that colors toast, darkens miso and builds aroma as it matures, while a higher share of koji makes miso sweeter and lighter.
| Feature | White (shiro) miso | Red (aka) miso |
|---|---|---|
| Typical aging | Shorter | Longer |
| Color | Pale yellow to beige | Reddish brown to dark brown |
| Flavor | Mild, slightly sweet | Deeper, saltier tasting |
| Common uses | Dressings, glazes, light soups | Hearty soups, braises, marinades |
| Sodium | Check the label | Check the label |
Yellow miso sits between the two. A sweeter taste does not mean less sodium, so compare labels rather than judging by color. For cooking, many recipes swap one for the other in a pinch, with darker miso used more sparingly because its flavor is stronger.
Miso soup and live microbes
Miso soup is the classic way to eat miso: miso paste stirred into dashi broth with tofu, seaweed or green onions. Its sodium depends on how much paste goes into each bowl and on the broth itself, so instant miso soup packets and restaurant bowls can differ widely. Packaged versions list sodium per serving on the label.
Miso is a fermented food, but that does not make every tub a probiotic. The 2021 ISAPP expert consensus explains that fermented foods and probiotics are different things, and that heating after fermentation kills the microbes. Some miso is heat processed before packaging, and boiling miso in soup has the same effect. A product can only claim live and active cultures if it was not processed to remove or kill them. Our guide to foods made by fermentation covers the live versus pasteurized question in more detail.
Miso benefits: what the evidence supports
Direct research on miso as a food is limited, and much of what circulates online comes from observational studies in Japan, where miso is eaten alongside many other foods. Those designs cannot show that miso itself causes any health outcome. What can be said plainly is narrower:
- It adds savory, umami flavor, so a small amount can season a dish of vegetables, tofu or grains.
- It is a soy food, and soy protein contains all nine essential amino acids, although a tablespoon of miso supplies only about 2 grams of protein.
- It is made by fermentation, which changes flavor and texture, but any live microbes are reduced by heat processing and cooking.
- Its sodium is significant, so it works well as a seasoning within an overall eating pattern that is not already high in salt.
Who should be careful with miso
- People with soy allergy: the FDA lists soybeans as one of the nine major food allergens, and miso is a soybean product.
- People on a sodium limit: if a clinician has set a sodium limit, for example for blood pressure, heart or kidney concerns, ask how miso fits rather than guessing.
- People avoiding gluten: barley is a gluten-containing grain under the FDA gluten-free rule, so barley miso is not gluten-free. Rice and soybean miso are not made from gluten grains, but people with celiac disease should look for a gluten-free label and talk to their clinician.
- People taking MAOI antidepressants: NCCIH reports interactions between high-tyramine soy products, such as soy sauce, and MAOIs that caused dangerously high blood pressure. Fermented soy seasonings deserve a conversation with the prescriber.
- People taking levothyroxine: MedlinePlus notes that foods containing soybeans may affect how levothyroxine works, so consistency and the prescriber’s timing advice matter.
Frequently Asked Questions
What is miso made of?
Soybeans, salt and koji, which is rice, barley or soybeans cultured with the mold Aspergillus oryzae. The mix ferments and matures for weeks to years.
Is miso healthy?
It adds flavor with few calories and small amounts of protein and minerals, but a tablespoon has about 28% of the Daily Value for sodium in USDA data.
What is the difference between white miso vs red miso?
White miso is usually aged for a shorter time and tastes milder and sweeter. Red miso is aged longer, darker and stronger in flavor. Sodium varies by brand.
Does miso soup have probiotics?
Not reliably. Many products are heat processed, and boiling kills microbes. Only foods with live and active cultures on the label still contain living microbes.
Is miso gluten free?
Not always. Barley miso contains gluten. Rice and soybean miso are not made from gluten grains, but check for a gluten-free label if you have celiac disease.
How long does miso last?
Follow the date and storage directions on the package. Most brands ask you to refrigerate the tub after opening.
Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement, especially if you take medicines, are pregnant or have a food allergy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Natto: USDA Nutrition, Vitamin K2, Warfarin and Soy Allergy Notes, Fermented Foods: List, Benefits and Live vs Pasteurized, Low Sodium Foods: USDA List, Foods High in Sodium and Label Terms.