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Miso is a fermented food made from soybeans, starch (rice or barley), and culture.
Fermenting foods involves enzyme action that converts the original product to the fermented form and limiting microbial growth. In the past, fermentation was used to preserve food because this process creates antimicrobial agents.
Miso fermentation takes place with koji, a mold culture of Aspergillus oryzae. (1) Miso has a long history with origination in Asia. The first book written about miso dates back to 702 AD, and it is thought that miso reductions began in the 200 BC to 300 AD period.
Nutritional Value of Miso Soup
Soybeans are naturally low in carbohydrates and are good sources of high-quality protein.
The primary type of carbohydrates in soybeans is oligosaccharides, which are poorly digested by human gastrointestinal enzymes, leading to the growth of beneficial bacteria in the colon. It is okay to eat miso soup when following a low-carbohydrate diet.
Miso is fermented before it is made available for consumption. Thus, it has additional benefits in comparison with plain soybeans. (2)
Varieties of Miso
Miso has many types that vary by region and have different taste, texture, and salt content.
White miso is mild and has less salt, whereas red miso is much stronger and saltier.
The taste, texture, and aroma of miso vary based on the ratio of soybean, salt, and koji mold and the duration of aging.
The koji used in miso making is high in two enzymes, namely, proteases and peptidases, which work to break down proteins into amino acids that give miso the characteristic umami flavor.
Miso is usually made with rice-koji starter, but in some regions of Japan, a barley-based koji is used. It is also common for Japanese families to make miso at home, especially in historic times. (7)
Popularity and Health Benefits of Miso
Fermented foods, particularly miso, have become quite popular in the United States recently due to their suggested health benefits.
Miso is primarily made from soy, and the high intake of soy products in both Japan and China has been thought to potentially contribute to the low rates of prostate and colon cancers in both countries. (1)
Here are some of the believed health benefits of miso:
- Decreases the risk of coronary heart disease: Miso intake can decrease cholesterol levels and help keep the blood vessels open and elastic. These effects are attributed to the plant’s content of sterols, vitamin E, and healthy unsaturated fats such as linoleic acid. (2)(7)
- Decreases the risk of cancer: The fiber, isoflavones, B vitamins, and antioxidants (mostly vitamin E) found in miso may reduce the risk of breast, prostate, and some gastrointestinal cancers. Miso may work by decreasing the effectiveness of carcinogens. (7)
- Promotes digestion: The natural enzymes in miso can aid digestion because of its probiotic properties. Miso also helps the body absorb some nutrients. (7)
- Decreases inflammatory markers: The isoflavones in miso may lead to lower levels of interleukin-6, an important marker of inflammation in the blood. (4)(5)
- Lowers the risk of hypertension: Intake of fermented soy, including miso, has been shown to decrease the likelihood of high blood pressure. (6)
Possible Side Effects and Risks of Miso Intake
Many studies have been conducted in Japan regarding the high intake of miso soup and possible stomach cancer risk, although the studies were of limited quality and produced conflicting results. (1)
Soy is rich in isoflavones, and the concern for women with cancer risk is related to the type of isoflavones being selective estrogen receptor modulators and phytoestrogens.
Animal studies make up most of the research with isoflavones and cancer risk, and the results do not have significant meaning for human response to soy intake. Countless human studies point to good safety and positive health benefits of soy. (2)
Miso is high in sodium (salt), and miso soup alone contributes about 10% of the daily sodium intake of Japanese people. It is well known that a high intake of sodium may contribute to hypertension (high blood pressure).
Studies on high-salt condiments in the Japanese diet, such as miso, did not show a strong association with different portion sizes and frequency of miso intake and hypertension rates. In addition, the isoflavones in fermented miso were shown to lower blood pressure, which means miso intake is likely not related to high blood pressure levels. (4)(6)
Miso should not be consumed by individuals with allergies to soy. Also, varieties of miso made with barley-koji should be avoided by individuals with celiac disease or gluten sensitivities.
Uses of Miso
Miso is a versatile ingredient that can be used for all three meals of the day, even for breakfast. Miso paste is most often used to make miso soup.
Miso soup is served mixed with seasonable vegetables for a simple breakfast and as a side dish or end of the meal for dinner. Miso is also great to mix into salad dressings, marinades, stews, ramen, and dips.
Miso soup is simple to make and delicious. There are many ways to make it. Traditionally, it is made by dissolving miso paste in water mixed with dashi (Japanese fish broth), small pieces of tofu, green onion, and dried Sakaemachi seaweed.
Note: It is important not to boil the miso paste, or it will lose its flavor and some of its active components.
Buying and Storing Miso
In the process of creating and fermenting miso, it must be stored in a cool, dry, dark place. After at least a month of fermentation, miso can be stored for several years.
Its long shelf life is due to its natural antimicrobial properties provided by the beneficial microbes created in the fermentation process. Commercially purchased miso is usually stored in the fridge to preserve its freshness.
Miso has gained so much popularity that it can now be purchased at most major grocery stores in the refrigerated Asian foods section. Asian grocers and online retailers have a greater variety of miso pastes readily available.
Miso is a versatile ingredient that adds fantastic flavor, texture, and umami taste to a variety of dishes. It is most traditionally used to make miso soup.
You can experiment with this ingredient and use it in many ways, such as in marinades for fish and meat, dressings, and dips for vegetables. Try the light and the darker red miso varieties as they are quite different.
Miso paste is high in salt. However, studies indicate that the salt in miso may not be related to increased blood pressure.
Check with your doctor or registered dietitian before making any significant diet changes. In conclusion, miso has many health and culinary benefits and can be added to any diet.