Back to Soy: Fermented vs. Unfermented

We love our tofu, and are not planning on giving it up any time soon, but Dr. Mercola’s (as well as many other nutritionist’s) case for passing on (or limiting) any unfermented soy products such as tofu is quite compelling.

The Healthy Aspects of Soy: Fermented vs. Unfermented

In order to back up the claim that soy is a health food, privately funded “researchers” have been quick to point out that Asians, who consume a diet high in soy, have less risk of breast, uterine and prostate cancer. Unfortunately, they leave out two very important

The reason Asians have an increased risk for some cancers is the same reason they do not develop others: unfermented soy. The soy marketing and promotion gurus left out this critical piece of information. Would you rather have one cancer over another? Isn’t that like asking whether or not you’d like to be whacked in the head with a two-by-four vs. a wooden stick?

You might be asking yourself what the big difference is between consuming a fermented soy product such as, say, tempeh, vs. tofu or a veggie burger. I’m here to tell you, the difference is night and day.

Unfermented AND fermented soy contains hormonal mimics in the form of isoflavones which can not only disrupt delicate hormone systems in your body, but also act as goitrogens, substances that suppress your thyroid function. When the thyroid is suppressed, a host of health problems result, namely:

  • Anxiety and mood swings
  • Insomnia
  • Difficulty losing weight
  • Difficulty conceiving children
  • Digestive problems
  • Food allergies

And so much more. No wonder soy can lead to thyroid, esophagus and stomach cancer! Unfermented soy is also chock full of phytic acid, an “antinutrient” responsible for leeching vital nutrients from your body. Phytic acid also blocks the uptake of essential minerals such as calcium, magnesium, copper, iron and zinc especially.

Now, fermented soy products do provide health benefits.

As I mentioned in my previous article, some examples of healthful fermented soyproducts are as follows:

  • Tempeh, a fermented soybean cake with a firm texture and nutty, mushroom-like flavor.
  • Miso, a fermented soybean paste with a salty, buttery texture (commonly used in miso soup).
  • Natto, fermented soybeans with a sticky texture and strong, cheese-like flavor.
  • Soy sauce, which is traditionally made by fermenting soybeans, salt and enzymes; be wary because many varieties on the market today are made artificially using a chemical process.

For those of you who enjoy tofu, I’m sorry to say it didn’t make this list because tofu is an unfermented soy product.

The claim that soy products can prevent osteoporosis, decrease your risk of cardiovascular disease and dementia and protect you from cancer of the prostate, lung and liver is actually true, but ONLY if the soy is fermented.


The process of fermenting soy destroys the above-mentioned dangerous substances, thereby making it fit for consumption. Also, fermented soy products such as those listed above are a rich source of vitamin K2, a vitamin that works in harmony with vitamin D to keep you healthy. Vitamin K regulates your body’s blood clotting ability and helps prevent cancer, osteoporosis and heart disease. And vitamin D is essential to the function of every system in your body.



  1. How do you reconcile the benefits of fermented soy listed in your article with the results of the following meta-analysis from Medline:

    Cancer Sci. 2011 Jan;102(1):231-44. doi: 10.1111/j.1349-7006.2010.01770.x. Epub 2010 Nov 10.

    Fermented and non-fermented soy food consumption and gastric cancer in Japanese and Korean populations: a meta-analysis of observational studies.

    Kim J, Kang M, Lee JS, Inoue M, Sasazuki S, Tsugane S.
    SourceCancer Epidemiology Branch, Research Institute, National Cancer Center, Goyang, Korea.

    Soy food is known to contribute greatly to a reduction in the risk of gastric cancer (GC). However, both Japanese and Korean populations have high incidence rates of GC despite the consumption of a wide variety of soy foods. One primary reason is that they consume fermented rather than non-fermented soy foods. In order to assess the varying effects of fermented and non-fermented soy intake on GC risk in these populations, we conducted a meta-analysis of published reports. Twenty studies assessing the effect of the consumption of fermented soy food on GC risk were included, and 17 studies assessing the effect of the consumption of non-fermented soy food on GC risk were included. We found that a high intake of fermented soy foods was significantly associated with an increased risk of GC (odds ratio [OR] = 1.22, 95% confidence interval [CI] = 1.02-1.44, I(2) = 71.48), whereas an increased intake of non-fermented soy foods was significantly associated with a decreased risk of GC (overall summary OR = 0.64, 95% CI = 0.54-0.77, I(2) = 64.27). These findings show that a high level of consumption of non-fermented soy foods, rather than fermented soy foods, is important in reducing GC risk.

  2. Great stuff Ron! Makes us even more weary of fermented soy — but as with everything there are benefits and risks. We thought Dr. Mercola’s explanation here was important to share b/c many people don’t realize there is a difference between the two types of soy -and would just think ‘tofu’ is always the healthy choice no matter what. We’d like to say a good approach to health is moderation, education, and luck (good genes) 😉 Thanks for sharing your report!

  3. I had seen a similar study published a decade earlier with similar conclusions. However, the earlier study addressed confounders or, as they are sometimes known, co-promoters. For example, the three main types of fermented soy (in terms of consumption) are miso, tempeh, natto, in that order. In the USA, at least, miso as sold contains a very high level of salt, whereas tempeh and natto contain relatively small amounts of salt. Salt may be a strong confounder in different cancers of the gastrointestinal tract. The earlier study left open the possibility that the excess cancers associated with fermented soy were mainly due to the high salt content of miso, the most studied of the fermented soy products. The earlier study also made the observation that people who ate large amounts of unfermented soy also ate large amounts of fruits and vegetables, and again these confounders served to reduce the incidence of cancer.

    Similar claims have also been made for kimchi, a cultured cabbage product. However, kimchi sold at Korean restaurants and Korean supermarkets (and, I would guess, sold in Korea) is very different from some of the kimchi sold at e.g. Whole Foods. The Korean-based variety is very high in sodium and hot spices, whereas some of the Whole Foods kimchi is low in both salt and spice.

    The real problem I see is that the biomedical literature contains results from a very different culture that prepares foods very differently, yet these results are being extrapolated blindly both in a positive and negative sense to American recommendations. Until we have a better understanding of all the variables that have an influence on the Korean results, we need to be very wary about drawing any conclusions from these Korean studies for the American diet.

    • thanks for pointing this out – we agree. We’ll keep this post up -as well as your comments – we hope people will read all the way through – if you have any sites you think are trustworthy sources -please share 😉

  4. Stephanie says:

    I am allergic to soy — are fermented soy products ok for me?


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