Yes, MISO is Awesome (But You Need to Know a Few Things Before You Eat It)

by Sarah Pope MGA | Affiliate linksComments: 13

light and dark miso

Did you ever wonder where and why there are so many soy foods in America? Tempeh, edamame, tofu, shoyu, miso, and so many others.

If you are looking for a book that helps explain it all, I highly recommend Hippie Food, which came out fairly recently. 

If the world of soy has you confused, let’s clear the air on miso. This traditional food that can be either a blessing or a burden to your health depending on how you source and use it.

Soy: Inherently Inedible

Soy in its natural state is a rather inedible crop.

It wasn’t until about a millennia ago when people figured out that certain microorganisms plus fermentation rendered it food worthy for humans. Traditionally, fermented soy was consumed in very small amounts as a condiment.

So, while humans have cultivated soybeans for a very long time, they conciously limited its consumption in raw or cooked form. Only in modern times did unfermented soy become a staple in the diet for some people, particularly vegetarians.

Traditional cultures purposely kept soy in the diet to a minimum because they noted its negative effects. Science tells us that soy is loaded with anti-nutrients.

How loaded? Even plant based diet advocates concede that unprocessed soy presents significant problems.

According to the American Nutrition Association:

The raw soybean contains numerous anti-nutrients. Although processing can reduce them, it does not eliminate them. The raw soybean is an anti-coagulant (an agent that prevents blood clotting). The anti-coagulant property is not reversed by vitamin K, which is a highly effective blood-clotting agent. (1)

Unfermented Soy Disrupts Protein Digestion and Risks B12 Deficiency

In addition to triggering blood clotting issues, soy has the potential to block the enzyme trypsin which is necessary for proper protein digestion.

In turn, trypsin allows Vitamin B12 assimilation in the body.

Ironically then, regular consumption of soybeans whether as green edamame beans or in processed foods as a “healthy plant protein” increase the odds of protein deficiency.

Those that rely heavily on soy as a protein source may very well find themselves with a Vitamin B12 deficiency too as trypsin permits proper assimilation of this vitamin.

As if this wasn’t enough, soy is one of the highest foods on the planet in phytates. This substance binds to minerals especially zinc, calcium and magnesium, hindering the body from utilizing them.

Hemagglutinins is yet another potent anti-nutrient in the raw soybean. These substances have an ability to agglutinate (clump together) the red blood cells in humans and in other animal species, and significantly suppress growth. These anti-nutrients are known also as “phytoagglutinins” or lectins. (2)

Techniques that Make Soy Edible

Over a thousand years ago, people began to develop techniques to reduce the large amount of anti-nutrients in soy so that both animals and people could safely eat it. And again, modern science makes it clear, this is the only safe way to consume soy.

The anti-nutrients present in soybeans are slightly reduced by heat processing and/or cooking. Sprouting of soybeans is more controversial. Some sources say it reduces anti-nutrients while others suggest it makes things worse.

No matter who is correct, these potent substances are still present in significant enough levels after sprouting to be problematic over time.

As a result, the only acceptable approach currently available to satisfactorily render soy edible is traditional fermentation.

This approach utilizes benefical microbes that trigger a slow and beneficial chemical change in the soybeans.

Enzyme and trypsin inhibitors, phytates, meagglutinins, and vitamin/mineral blockers are all neutralized. Thus, consuming fermented soybeans renders this legume’s nutrients available and readily digestible by the human intestinal tract.

Miso Defined

Miso is the result of employing traditional fermentation techniques on cooked soybeans over a very long period of time.

Similar to natto, miso is made by first cooking soybeans and then inoculating the mixture with microorganisms.

With natto, it is bacteria. With miso, it is mold … technically, fungus. Specifically, the fungus koji (Aspergillus oryzae).

What? Miso Fermented with Mold??

Miso production dates back to before 700 AD. The food was so popular, the emperor established a bureau to oversee its production and trade, and of course, the taxes applied to it! (3)

Similar to natto, there is no one miso. Rather, miso is made by a general set of techniques and inputs, but miso makers, by playing with these variables, can create a wide range of final products that may vary substantially from one another.

For instance, they may use fungi cultured from rice (kome-miso), barley (mugi-miso), or soybeans alone (mame-miso) among other possible options. The final product may contain a mixture of main ingredients. (4)

More specifics are detailed in the cookbook The Japanese Kitchen by Hiroko Shimbo.

Types of Miso

Believe it or not there are over 1000 types of miso! Red miso, white miso, brown rice miso … and nearly every shade in between!

Producing authentic miso is a truly artisanal craft that requires time and patience similar to balsamic vinegar and wine among other coveted foods.

Thankfully, we can make the choice of what miso to use a little simpler.

Most miso is either light or dark.

Light miso is sweet – the product of a higher proportion of koji to soybean and a shorter time fermenting. This is the type typically served at Japanese restaurants in America. I use this reputable brand of white miso and have for years.

Dark miso is pungent – more soybeans, more salt, and more time spent fermenting make this a hearty, strongly scented and flavored final product. I prefer this brand of dark miso.

If you didn’t already guess, white misos are generally the place to start for those wanting to dabble in this food.

Ingredients should ONLY include organic whole soybeans, water, sea salt and koji. Acceptable optional ingredients are brown rice or barley. 

But why would you want to try out miso? Let’s look at its nutrition and possible health benefits.

Nutrition and Health Benefits

As mentioned above, humankind has consumed miso for over a thousand years for good reason.

First, since miso is cultured, it is a probiotic food, providing a host of benefits that living foods provide. The probiotic benefits extend beyond just good microbes.

Miso provides the elusive vitamin K2, enzymes, B-12, and more! The vitamin K2 in miso is the MK-7 rather than the animal form known as MK-4.

Miso is a good source of a number of minerals, such as copper, manganese, phosphorus, and zinc. No wonder proper preparation to eliminate phytates is so important. Without it, these wonderful minerals go unutilized by the digestive tract!

Miso is high in salt – one teaspoon generally contains 200-300 milligrams. Hence, those on sodium restricted diets may need to exercise caution and care with their miso consumption. Another option is to look for lower salt varieties.

When it comes to claims about heart, cancer, and other benefits and protections, the science is at best mixed on miso and other soy foods.  So, for the time being, take these claims with a grain of  salt … in your miso! (5)

Miso Dangers

Like any soy food, you should only consume organically grown, traditionally prepared miso-based products.

Soy is one of the world’s most heavily sprayed, unsafe GM crops. So conventional soy, regardless of preparation, is a health and environmental risk not worth taking.

Most restaurants serve miso soup made from GMO soybeans. Sometimes GMO tofu cubes are added. It is best to skip ordering this dish at a Japanese restaurant unless the menu specifically notes the use of organic ingredients.

The best of the best is generally made either at home, by small artisans, or by reputable outfits with larger distribution, but who still follow traditional methods and practices.

Other than high salt, miso has few risks, beyond those inherent to all soy foods.

The presence of thyroid suppressing goitrogens that because of pre-existing health conditions, iodine deficiency, or a general overconsumption of soy foods in lieu of the perfectly balanced proteins in animal foods can cause problems.

One final caution is for those sensitive to molds. Because miso is fermented with the fungus Aspergillus oryzae, it might be best to avoid it for that reason alone.

Is Miso Gluten Free?

Some types of miso are not gluten free. These would include those fermented with brown rice or barley.

If you are gluten sensitive or Celiac, be sure to source only mame-miso, made from soybeans, water, sea salt and koji alone.

Isoflavone Risks of Miso

Good news!

It does appear that some of the isoflovene risks of soy foods is muted in miso compared with other forms of soy.

Some of the health benefits provided by soy foods depend on the ability of bacteria or other micro-organisms to break down two of the soy’s isoflavones – daidzein and genistein—into related compounds (for example, equol). Interestingly, recent research has shown that many different strains of the fungus Aspergillus oryzae—by far the most widely-used fungus in the fermentation of miso—are capable of breaking down both daidzein and genistein. This finding is great news for anyone who already enjoys miso, or is considering adding miso to their diet.

If micro-organisms used in miso fermentation don’t break down some of the daidzein and genistein into other compounds like equol, it’s up to the micro-organisms in our digestive tract to do so. While it is fantastic when we have the right balance of micro-organisms in our digestive tract to help us get optimal nourishment and health benefits from our food, those conditions don’t always hold true. So it can be very helpful when a miso-fermenting fungus like Aspergillus oryzae helps breaks down the daidzein and genistein before the miso ever reaches our digestive tract! (6)

This is promising information indeed. Future research will hopefully shed even more light on this beneficial aspect of miso production.

Note that just because isoflavones in miso are potentially broken down by Aspergillus oryzae, doesn’t mean they are not in fact present in a form that is hormonally disruptive in some way.

In other words, don’t operate under the assumption that miso poses no hormonal risks whatsoever if you have a pre-existing condition in this area. Exercise caution and consult with your practitioner before deciding to consume it regularly.

Storage and Shelf Life

Since miso is a living food containing numerous beneficial enzymes and probiotics, it requires proper storage. Refrigeration is best, although a cool, dark cellar can work too if you live in a northern clime.

Never keep it in a warm kitchen pantry or cabinet.

Color, smell, and flavor can change during storage and frequently do. Hence, it is best to consume it in a timely fashion, usually within a few weeks after opening.

That said, because it is fermented, a container of miso will last in the refrigerator for months and months much like homemade sauerkraut. If it doesn’t have mold, it can still be eaten. But, you might not enjoy the flavor as well if it is months old.

How to Serve Miso Properly

The traditional way to serve miso is as a soup. Simply blending the miso paste into hot water or bonito broth is all that is required.

Sometimes, a few small cubes of bean curd and kombu are added.

Since miso is a living food, blending into a liquid that is too hot negates much of the health benefit!

As a result, take care to ensure that the water or broth is no more than 117 F degrees (47 C) when it contacts the miso. This is the liquid temperature above which enzymes and probiotics are destroyed.

A quick read from a digital food thermometer is all that you need. This is a must have tool in the kitchen if one of your goals is to maximize nutrients in your dishes.

Making the Most of Miso’s Many Health Benefits

Another reason miso is so popular is because it adds umami – the fifth taste – to most any dish which includes it. One of my favorites is this Italian vegetable soup that uses dark miso as the soup base. This tomato based recipe for miso soup is another tasty try.

If you enjoy noodles, try this miso ramen dish too.

Especially for those restricting or unable to access sufficient meat, miso makes a good substitute to provide deep, rich flavors that are otherwise lacking.

Remember, miso is a condiment or small addition to dishes, so treat it as such. Use it to bolster the flavor of a soup or similar dish, or mixed into salad dressing or similar spreads and dips to add flavor and nutrition. It works great as part of a marinade, and has a long history of use with fish and other seafood.


(1, 2) American Nutrition Association. The Downside of Soybean Consumption

(3, 4) What is Miso?

(5, 6) What’s New and Beneficial about Miso

Posted under: Healthy Living

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