Is Miso Good for Gut Health?

Partly: miso may support gut health as part of a varied diet because fermentation changes its ingredients and some products contain live microorganisms, but a benefit from eating miso has not been established. Human evidence specific to miso and gastrointestinal health is limited, so it should not be treated as a remedy.

Is miso good for gut health?

Miso can be a flavorful addition to a diet that supports gut health, but fermentation alone does not guarantee a measurable benefit. Its possible effects depend on the product, how it is prepared and the rest of your diet.

Consider miso alongside a variety of best foods for gut health, rather than relying on it as your main strategy. For a related look at hydration, see the best drinks for gut health.

How might miso work in the gut?

Miso is a fermented paste usually made from soybeans, salt and a culture called koji. It can also contain grains such as rice or barley. During fermentation, microorganisms and their enzymes transform components of those ingredients, creating miso’s characteristic flavor and other compounds.

Some miso products contain live microorganisms that could interact with the gut environment. Others are pasteurized, which kills live microorganisms. Even when a product contains live cultures, you cannot assume they will survive digestion or produce a particular health benefit.

Fermentation can also change compounds in soybeans, but researchers have not established which changes in miso, if any, meaningfully improve human gut health. Miso is not a proven substitute for a varied diet that includes fiber-containing foods.

Fermented does not automatically mean probiotic. A probiotic is a live microorganism shown to provide a health benefit when consumed in an adequate amount. A fermented product may contain live microbes without having evidence that they meet that definition.

What does the evidence say about miso?

A 2019 review of fermented foods and gastrointestinal health found no randomized controlled trials investigating miso’s gastrointestinal effects at the time of the review. It described several possible mechanisms for fermented foods, including effects from microorganisms and compounds produced during fermentation, but potential mechanisms are not proof of a benefit in people.

The review found trials for some other fermented foods. Those results cannot establish that miso has the same effects: ingredients, microorganisms and preparation methods differ. The review also does not establish that miso improves a particular symptom or treats a digestive condition.

For now, it is reasonable to eat miso if you enjoy it and tolerate it. It is not possible to recommend a specific amount of miso as an evidence-based way to improve gut health.

How can you use miso for gut health?

Choose a miso that fits your taste and dietary needs. If live cultures matter to you, check the label for information about whether the product is pasteurized or contains live cultures. Label wording varies, and the presence of live cultures does not prove the finished food has a probiotic benefit.

Mix miso into warm water or soup after cooking rather than boiling it if you want to avoid exposing any live cultures to high heat. Heat can kill microorganisms, although adding miso after cooking does not guarantee that the product contains live cultures or that they will benefit your gut.

You can also use miso to season vegetables or other foods you already eat. Keep the whole meal in mind: miso can add flavor, while a variety of fiber-containing foods contributes to a balanced eating pattern. Follow the package instructions for storage and check the label for sodium and allergens.

Who should be careful with miso?

Miso can be high in sodium. If you have high blood pressure, heart failure or kidney disease, or have been advised to limit sodium, check the nutrition label and ask your clinician or dietitian how miso fits your plan. Compare sodium per serving and consider how much miso you actually use.

Check ingredients if you have a soy allergy: miso usually contains soybeans. Some products contain barley or other gluten-containing grains, so people with celiac disease or a gluten-related disorder should look for a suitable gluten-free product. For children or during pregnancy, check ingredients and sodium and follow the product’s storage instructions; ask a healthcare professional about individual dietary concerns.

See a clinician for persistent or worsening digestive symptoms or unexplained weight loss. Seek urgent care for severe abdominal pain, bloody or black stools, or signs of severe dehydration such as fainting or confusion. Miso should not replace assessment or prescribed treatment.