Fermented Soy vs Unfermented Soy

A breakdown on unfermented and fermented soy - and which one you should minimize in your diet!

Fermented Soy vs Unfermented Soy
Photo by Wouter Supardi Salari / Unsplash
5 min. read 2/11/2022, 4:41 PM

It's not uncommon for people to find out that one of their favorite "healthy foods" is actually not so healthy after all. One of those is soy. Soy is a legume that is often used as a plant protein source and as an ingredient in meat alternatives. Before you start to worry – not all soy is bad! There are two types, and one is better than the other.

The two types of soy are fermented and unfermented, and both are found in common foods that vegans and non-vegans eat. However, one type is being promoted as a healthy source of protein when in reality consuming too much of it can be damaging...

So, which one is healthy and which one isn't?

Keep on reading to learn everything about fermented soy vs unfermented soy!

What is fermented soy?

It's a type of soy that goes through a long fermentation process. Fermented soy is cultured with beneficial bacteria, yeast, or mold. It's commonly consumed in Asian countries, but various great fermented products are increasing in popularity in the U.S. as well.

The question is... is fermented soy bad for you?

No, it's actually really good for you! Fermented soy is packed with good bacteria and/or probiotics found that help nourishes gut health, boost digestion, and improve the absorption of nutrients. Another benefit they provide is the high content of vitamin K2. Vitamin K2 is an important nutrient that supports cardiovascular and bone health. What makes fermented soy even better is that it contains the perfect form of vitamin K - menaquinone, MK for short. This type of vitamin provides several benefits and it stays in your body longer. It's difficult to get this vitamin from other food sources, so your best bet is to get it from fermented foods.

Best fermented soy products

If you want to improve your gut health or want to boost your protein intake, try these fermented soy foods...

  • Tempeh: This is a fermented soybean cake that is very similar to tofu. The difference is that it is fermented, unlike tofu, and has a different flavor and texture. Tempeh has an earthy and nutty flavor. And it's packed with protein (15 grams per 3 ounces serving), fiber, and other great vitamins and nutrients!
  • Miso: This is a fermented soybean paste that is commonly used in miso soup. It has an umami-rich flavor that makes for an excellent and nutritious broth!
  • Natto: This is fermented soybeans that have a slimy, gooey texture. Although the texture may be off-putting to some, natto is the best source of vitamin K2 and has 18 grams of protein per 3-ounce serving! Mix it with some rice and top it with soy sauce, mustard, or chives to give it a delicious flavor.

What is unfermented soy?

Unfermented soy is basically soy that has not gone through the fermentation process. The problem with this is that soybeans contain anti-nutrients, which include saponins, soya toxin, phytates, trypsin inhibitors, goitrogens, and phytoestrogens. When soy undergoes fermentation it destroys all those anti-nutrients so that the body receives all the nutritional benefits. This leaves unfermented soy to contain all these anti-nutrients that can have adverse effects on the body.

The unfermented soy dangers

Unfermented soy is an anti-nutrient. This means that it will keep your body from absorbing minerals like calcium, magnesium, and especially zinc (all minerals that your body needs to function properly). This can lead to a mineral deficiency, especially for those who don't eat meat.

Aside from messing with your nutrient absorption, here are other dangers of consuming too much unfermented soy:

  • It can cause gastric distress: Eating more than just 35 grams can lead to stomach issues and a nutrient deficiency, especially amino acids which are extremely important.
  • It can keep your body from absorbing proteins: Anti-nutrients have potent enzyme inhibitors that block the action of trypsin (an enzyme needed for protein digestion). This won't stop your gains altogether, but it will make it harder to build muscle... and muscle isn't the only part in your body it can affect. It can also affect your skin, your hair, your bones, your teeth, and your nails.
  • It can impact thyroid function: Soy contains goitrogens which are a substance that blocks the synthesis of your thyroid hormones and mess with iodine metabolism. This leads to lowering thyroid function, which can lead to anxiety, digestive issues, weight gain, food allergies, and other problems.
  • It can mimic or block estrogen: Soybeans are rich in the compounds isoflavones, genistein, and daidzein - a type of phytoestrogen. These compounds resemble human estrogen, they disrupt endocrine function and can have adverse effects on human tissues. Research and studies suggest that high levels of soy isoflavones can lead to infertility.[1]
  • Soybean grown in the U.S. is genetically modified: Over 90% of the soybeans grown in the U.S. are genetically modified, making them GMO. They are engineered to survive being heavily sprayed with chemical herbicides. As you can imagine, this can have terrible effects on one's health.

Common unfermented soy products

Despite there being some serious dangers that come with unfermented soy, you have to consume a lot of it to kick up those adverse effects. So, knowing which soy products you should cut back on is important.

The most popular unfermented soy products include...

  • Soybeans
  • Soy milk
  • Vegan meat substitutes
  • Tofu
  • Soy protein isolate (in protein bars and shakes)
  • Edamame
  • Soy cheese
  • Vegetable oils

To maintain an adequate intake of soy and avoid its potential dangers of it, consume no more than 15-25 grams per day, or 2-4 servings of soy foods per day. Also, opt for fermented soy or the less processed unfermented soy, like tofu and edamame.

To summarize, fermented soy is healthy and is great for improving digestion and gut health. While unfermented soy can be unhealthy, but only when consumed in high amounts. Don't let this scare you away from consuming soy, just be more mindful of what type of soy foods you eat and how much. Try to purchase high-quality organic soy as opposed to the unfermented GMO soy. If you do choose to eat unfermented then keep your soy consumption below 25 grams!