Published 13th June 2022

Miso: All you need to know

Miso is a fermented soybean paste from Japan that adds a deep, savory flavor to a range of dishes. There are many varieties, which can enhance the taste of any meal. 

Miso soup is known worldwide, but miso can bring additional umami richness to just about anything — even cakes.

Beyond its flavor, there is some evidence that it might also benefit health, although research is relatively limited.

For instance, some studies have concluded that miso might protect against certain cancers and heart disease in women. Plus, because it’s a fermented food, it might help nourish and balance the community of bacteria that live in your gut. 

In this article, we’ll explain what miso is and how it’s made. We’ll also look at the evidence for health benefits. 

At ZOE, we know that foods affect people in different ways. Our at-home test analyzes your gut microbiome. It also explores how your blood sugar levels and blood fat levels respond to different foods. Using this personalized information, our scientists can recommend foods that work best for your body.

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What is miso?

Miso is a fermented soybean paste that’s a staple of Japanese cuisine and other East Asian food cultures. Dating back thousands of years, miso is prized for its umami flavor. 

Miso producers make it by fermenting a soybean paste in a mold called koji (Aspergillus oryzae). They ferment it for different lengths of time — it can take weeks or years, depending on how strong you want it to taste. 

Miso makers cultivate this mold from rice, soybeans, or barley, and the enzymes in the mold team up with microorganisms in the environment to ferment the soybean paste and deepen its flavor.

It’s also possible to make miso-like products from farro or legumes and pulses like chickpeas, lima beans, or adzuki beans. Technically, these products are not miso, but they add an umami lift that can substitute for miso if you can’t (or don’t) eat soy.

While miso is incredibly versatile, it’s perhaps best known as the primary ingredient in miso soup. Miso can be part of a vegan or vegetarian diet, but traditional miso soup includes bonito flakes, which are dried fish, so it wouldn’t be suitable for people who don’t eat animal products. 

What affects miso’s flavor?

There are many varieties of miso, and several factors influence their taste:

  • The location. Geographical location can affect how miso tastes, as environmental conditions in the local area can alter how the microorganisms interact with the paste and koji.

  • Using different starter cultures. There are hundreds of ways to make miso, and the specific mold or yeast that ferments the soybean paste can affect the flavor by changing the acidity of the miso.

  • Its color. The longer miso ferments, the darker its color will be and the stronger it will taste.

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Varieties of miso

The range of miso varieties in Japan makes it possible to add it to every meal, although outside of Asia, there are fewer options.

Here are some of the more common forms of miso, how they taste, and ways to use them:

White miso

White miso is also called sweet miso, Shiro miso, or mellow miso. It provides a milder and more adaptable flavor due to its shorter fermentation period. 

As suggested by its name, it’s the lightest miso variety and is delicious in light soups and dressings. It’s sweet miso that adds the best flavor to desserts without overpowering their sweetness.

Red miso

Also called dark miso, this type has a much heavier, denser flavor and a more potent aroma that lends it to more robust soups, marinades, and glazes. 

It provides such a strong taste that not much is necessary to dominate a meal’s flavor, so it only takes a small amount to lift an entire dish. The fermentation process is much longer for dark miso — sometimes taking years.

Introducing red miso to meat and protein dishes can inject fresh life into your steak or tofu.

Yellow miso

Yellow miso, or Shinshu miso, is the Goldilocks of miso varieties — slightly stronger than white miso and less overpowering than red miso. While it can work best in soups and glazes, there isn’t a meal that yellow miso doesn’t make better. 

6 ways to use miso

There are so many ways to elevate a meal with miso — here are just a few ways to put it to work.

  • Salad dressing. There’s no need to cook miso, so if you’ve prepared a salad dressing (or even have a store-bought one), throw in some miso and stir it up for an extra flavor boost.

  • Marinades and glazes. You’ll need to water it down or add oil/butter to remove miso’s characteristic clumpiness, but miso makes for a powerful marinade that adds depth to vegetarian or vegan protein options.

  • Sandwich fillings. Add miso to cream cheese, mayo, or ranch, and slather it over your sandwiches before adding other fillings.

  • Stir-fries. Before you add your fish sauce, soy sauce, or teriyaki to a stir-fry, mix some miso into the liquid as a flavor enhancer.

  • Stews, chilies, and soups (and not only miso soup). Any broth or creamy offering can gain extra depth and saltiness from a miso injection. Throw it in toward the end of your simmer to avoid losing that distinctive flavor.

  • Pestos. Your pasta dishes aren’t immune to miso’s charms, and the paste combines with pesto to add a distinctive earthiness to your pestos and sauces.

Given that miso contains live cultures, it’s best to store it in your refrigerator. However, you can keep miso in the freezer for a few months at temperatures higher than 25 degrees Fahrenheit (-5 degrees Celsius). 

You can also keep miso in your pantry for a few months without it spoiling.

Does miso provide any health benefits?

Research supports some potential benefits of eating miso as part of a balanced, nutritious diet. 

Blood glucose control

Some studies have shown that miso soup can help improve the body’s ability to control blood sugar. 

One 2021 study found that women with type 2 diabetes who consumed miso soup every day had lower HbA1c levels than those who didn’t. HbA1c is a way of measuring blood sugar control over 2–3 months. The researchers didn’t find the same effect in men.

Eating miso soup every day was associated with lower insulin resistance in a 2018 study carried out in Japan. Insulin resistance means that your cells respond less well to insulin, making blood sugar spikes more likely. 

ZOE’s research has shown large differences in blood sugar responses between people. Some individuals may experience large spikes in blood sugar after eating a particular food, while others don't. A rise in blood sugar after eating is normal, but regular blood sugar spikes can increase your risk of type 2 diabetes and heart disease. 

If you want to understand how your blood sugar levels respond to food, start by taking our free quiz today.

Miso and cancer risk

Only a few studies have focused on miso’s effects on cancer risk specifically. Most research focuses on soy in general. For instance, some research has identified links between consuming soy products and a reduced risk of prostate cancer

Other studies have found links between soy consumption and reduced breast cancer recurrence and mortality in women. 

Also, a 2020 study found that consuming seaweed and soy was associated with a lower risk of death in people with colorectal and stomach cancer. 

There is some evidence that miso may reduce the risk of liver cancer in men, but soy does not. Also, regularly eating miso soup may be linked to a reduced risk of breast cancer in women.

Other research, however, tells a different story. A 2017 meta-analysis of 13 studies found that high miso soup intake might increase the risk of gastric cancer in males. The authors conclude that “high intake of nonfermented soy food might reduce the risk of [gastric cancer], while high intake of miso soup might increase the risk in male[s].”

Another analysis, which reviewed 22 studies, also linked regular miso soup consumption to an increased risk of gastric cancer.

The authors of both reviews suggest that this increased risk in gastric cancer might be due to the high levels of salt in miso.

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Other possible health benefits of miso

According to one study, fermented soy products like miso might reduce the risk of heart disease in women. 

Plus, miso is probiotic, so it might boost your gut microbiome. This could provide health benefits throughout the body and possibly reduce inflammation.

Good heart health, lower cancer risk, and stable blood sugar levels depend on more than a single type of food, though.

ZOE runs the largest ongoing nutrition science study in the world. We know that gut bacteria are vital for good health and that everyone has a unique gut microbiome. If you'd like to learn more about the gut bacteria that currently live in your gut, take our free quiz today.

With our at-home test, we can also test how your blood sugar and blood fat levels respond to different foods. Using this information, we can provide you with personalized nutrition advice, allowing you to eat the best foods for your body. 

Summary

Miso is a fermented soybean paste that first appeared in Japanese cuisine. It adds savory umami depth to soups, salads, veggie protein, meats, and even cakes and desserts. 

Its color ranges from light to dark, and there are hundreds of varieties that range from sweet and mild to rich and pungent. Miso is easy to stir into sauces and marinades, and you can store it for months in your pantry or refrigerator.

As a fermented food, miso may provide probiotic benefits for your gut. It might also help people with type 2 diabetes control blood sugar and reduce the risk of some types of cancer. However, scientists need to carry out more research into these potential health benefits.

To truly eat a diet that’s tailored to your body, ZOE’s at-home test can provide a picture of which foods suit your body best.

Take our free quiz to learn how ZOE can help you move toward your long-term health goals.

Sources

Associations of Japanese food intake with survival of stomach and colorectal cancer: A prospective patient cohort study. Cancer Science. (2020). https://onlinelibrary.wiley.com/doi/full/10.1111/cas.14459 

Comparison between the impact of fermented and unfermented soy intake on the risk of liver cancer: the JPHC Study. European Journal of Nutrition. (2020). https://link.springer.com/article/10.1007/s00394-020-02335-9 

Diabetes, heart disease, & stroke. (2021). https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/heart-disease-stroke 

Dietary habits associated with reduced insulin resistance: The Nagahama study. Diabetes Research and Clinical Practice. (2018). https://www.sciencedirect.com/science/article/abs/pii/S0168822717319459 

Fermentation and the microbial community of Japanese koji and miso: A review. Journal of Food Science. (2021). https://ift.onlinelibrary.wiley.com/doi/full/10.1111/1750-3841.15773 

Fermented soy products intake and risk of cardiovascular disease and total cancer incidence: The Japan Public Health Center-based Prospective Study. Nutrition and Health. (2020). https://www.nature.com/articles/s41430-020-00732-1 

Habitual miso (fermented soybean paste) consumption is associated with glycemic variability in patients with type 2 diabetes: A cross-sectional study. Nutrients. (2021). https://www.mdpi.com/2072-6643/13/5/1488 

Health benefits of fermented foods. Critical Reviews in Food and Science Nutrition. (2017). https://www.tandfonline.com/doi/abs/10.1080/10408398.2017.1383355 

Impact of soy foods on the development of breast cancer and the prognosis of breast cancer patients. Complementary Medicine Research. (2016). https://www.karger.com/Article/Abstract/444735 

Meta-analysis of soy consumption and gastrointestinal cancer risk. Scientific Reports. (2022). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481399/ 

Soy consumption and the risk of prostate cancer: An updated systematic review and meta-analysis. Nutrients. (2018). https://www.mdpi.com/2072-6643/10/1/40 

Soy food intake and risk of gastric cancer. Medicine (Baltimore). (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5571710/ 

Soy, isoflavones, and breast cancer risk in Japan. Journal of the National Cancer Institute. (2003). https://pubmed.ncbi.nlm.nih.gov/12813174/