What Is Miso?
This traditional Japanese condiment consists of a thick paste made from soybeans that have been fermented with salt and a koji starter.
The starter usually contains the Aspergillus oryzae fungus.
Miso paste can be used to make sauces, spreads and soup stock, or to pickle vegetables and meat.
People generally describe its flavor as a combination of salty and umami (savory), and its color can vary between white, yellow, red or brown, depending on variety.
Although miso is traditionally made from soybeans, certain varieties use other types of beans or peas.
Other ingredients may also be used to make it, including rice, barley, rye, buckwheat and hemp seeds, all of which affect the color and flavor of the final product.
It’s Rich in Several Nutrients
Miso contains a good amount of vitamins, minerals and beneficial plant compounds. One ounce (28 grams) generally provides you with:
- Calories: 56
- Carbs: 7 grams
- Fat: 2 grams
- Protein: 3 grams
- Sodium: 43% of the RDI
- Manganese: 12% of the RDI
- Vitamin K: 10% of the RDI
- Copper: 6% of the RDI
- Zinc: 5% of the RDI
It also contains smaller amounts of B vitamins, calcium, iron, magnesium, selenium and phosphorus, and is a source of choline.
Interestingly, the varieties made from soybeans are considered to be sources of complete protein because they contain all the essential amino acids needed for human health.
Moreover, the fermentation process used to produce miso makes it easier for the body to absorb the nutrients it contains.
The fermentation process also promotes the growth of probiotics, beneficial bacteria that provide a wide array of health benefits. A. oryzae is the main probiotic strain found in miso.
That said, miso is also very salty. Thus, if you’re watching your salt intake, you may want to ask your health care practitioner before adding large quantities to your diet.
Miso Improves Your Digestion
Your gut is home to trillions of bacteria.
Some are beneficial, while others are harmful. Having the right type of bacteria in your gut helps you maintain a healthy gut flora.
Having a healthy gut flora is very important because it helps defend your body against toxins and harmful bacteria. It also improves digestion and reduces gas, constipation and antibiotic-related diarrhea or bloating.
A. oryzae is the main probiotic strain found in miso. Research shows that the probiotics in this condiment may help reduce symptoms linked to digestive problems including inflammatory bowel disease (IBD).
In addition, the fermentation process also helps improve digestion by reducing the amount of antinutrients miso contains.
Antinutrients are compounds naturally found in foods, including in the soybeans and grains used to produce miso. If you consume antinutrients, they can bind to nutrients in your gut, reducing your body’s ability to absorb them.
Fermentation reduces antinutrient levels in miso and other fermented products, which helps improve digestion.
May Reduce the Risk of Certain Cancers
Miso may offer protection from certain types of cancer.
The first may be stomach cancer. Observational studies have repeatedly found a link between high-salt diets and stomach cancer.
However, despite its high salt content, miso doesn’t appear to increase the risk of stomach cancer the way other high-salt foods do.
For instance, one study compared miso to salt-containing foods such as salted fish, processed meats and pickled foods.
The fish, meat and pickled foods were linked to a 24–27% higher risk of stomach cancer, whereas miso wasn’t linked to any increased risk.
Experts believe this may be due to beneficial compounds found in soy, which potentially counter the cancer-promoting effects of salt.
Animal studies also report that eating miso may reduce the risk of lung, colon, stomach and breast cancers. This seems especially true for varieties that are fermented for 180 days or longer.
Miso fermentation can last anywhere from a few weeks to as long as three years. Generally speaking, longer fermentation times produce darker, stronger-tasting miso.
In humans, studies report that regular miso consumption may reduce the risk of liver and breast cancer by 50–54%. The breast-cancer protection appears especially beneficial for postmenopausal women.
This condiment is also rich in antioxidants, which may help guard your body’s cells against damage from free radicals, a type of cell damage linked to cancer.
Nevertheless, more studies are needed before strong conclusions can be made.
It May Strengthen Your Immune System
Miso contains nutrients that may help your immune system function optimally.
For instance, the probiotics in miso may help strengthen your gut flora, in turn boosting immunity and reducing the growth of harmful bacteria.
Moreover, a probiotic-rich diet may help reduce your risk of being sick and help you recover faster from infections, such as the common cold.
In addition, regularly consuming probiotic-rich foods like miso may reduce the need for infection-fighting antibiotics by up to 33%.
That said, different probiotic strains can have different effects on your health. More studies are needed using miso-specific strains before strong conclusions can be made.
Other Potential Benefits
This Japanese condiment may offer an array of other health benefits:
- May promote heart health: Miso soup may reduce the risk of death from heart disease. However, the protective effects appear to be small and may be specific to Japanese women.
- May reduce cholesterol levels: Animal studies show that miso may help reduce levels of “bad” LDL cholesterol in the blood.
- May reduce blood pressure: Miso appears to reduce blood pressure in animals. However, results in humans remain divided.
- May protect against type 2 diabetes: Some studies show that fermented soy products such as miso may help delay the progression of type 2 diabetes. However, not all studies agree.
- May promote brain health: Probiotic-rich foods such as miso may benefit brain health by helping improve memory and reducing symptoms of anxiety, stress, depression, autism and obsessive-compulsive disorder (OCD).
Although these added benefits are encouraging, it’s good to note that few studies directly link regular miso to the above benefits. More research is needed.
Is Miso Safe?
Miso consumption is generally safe for most people.
However, it does contain a large amount of salt. Thus, it may not be a good choice for individuals who need to limit their salt intake due to a medical condition.
In addition, miso is relatively high in vitamin K1, which can act as a blood thinner. If you’re taking blood-thinning medications, make sure you consult your health care practitioner before adding it to your diet.
Finally, most varieties are made from soybeans, which could be considered a goitrogen.
Goitrogens are compounds that may interfere with the normal functioning of the thyroid gland, especially in those who already have poor thyroid function.
That said, when goitrogen-containing foods are cooked and consumed in moderation, they are likely safe for all individuals — even those with thyroid problems.
How to Shop for Miso and How to Use It
In Europe or North America, you can find miso in most Asian grocery stores, as well as some conventional grocery stores.
When you’re shopping for miso, consider that color can be a good indicator of taste. That is, darker colors are generally linked with a stronger, saltier taste.
Moreover, it isn’t too difficult to make at home. It only requires a few ingredients and some patience. If you want to try it, you can start with this simple recipe (video).
Miso is extremely versatile and can be used in a variety of ways. For instance, you can use it to flavor a broth, marinade or casserole.
You can also blend it with ingredients such as peanut butter, tofu, lemon or apple juice to make dipping sauces or spreads. When combined with oil and vinegar, it yields a simple and tasty salad dressing.
Miso may be best used in cold rather than hot dishes, since its probiotics can be killed by high temperatures. That said, some heat-killed probiotic strains may still provide some benefits, so this topic remains controversial.
Unopened miso paste can be kept at room temperature for long periods of time.
However, once you’ve opened it, make sure to store it in the refrigerator in a closed container and ideally consume it within a year of purchase.