Vegetarian Diet - Dangers of Unfermented Soy

Written By Denise Tam, Holistic Nutritionist

With vegan and vegetarian diets on the rise, many people are turning to soy for their source of protein. In many of the fake meats like Beyond Meat, Impossible and Omnipork, you will surely find soy protein as one of the main ingredients. Look further and you’ll find soy in protein bars, baked goods, sports drinks and even in baby formula. The consumption of soy as food has been around for a long time. Soy is not new to our diet especially in Asia, however the soy that we now intake is very different from the soy of ancient days. Majority of the soy found in our food is genetically modified (around 99%), heavily processed, or a soy concentrate or isolate. Mary Enig, PhD, explained that "The reason there's so much soy in America is because the soy industry started to plant soy to extract the oil from it and soy oil became a very large industry." Soy protein is a by-product from the oil and so the industry and companies needed to find a way to use this cheap by-product.

Although soy has its benefits, just how healthy are our modern day sources of soy? 

Nutrient Blocking Phytic Acid

Soy is a legume, like adzuki, red kidney, navy, chickpeas etc. All legumes and whole-grains such as rice, barley, oats, wheat and rye contain some amounts of phytic acid. Soy is considered high in phytic acid. Phytic acid acts as a binder in our intestinal tract and in large amounts it can block the uptake of essential minerals like calcium, magnesium, copper, iron and especially zinc. Soy also inhibits the uptake of one of the most important minerals needed for growth and metabolism, iodine, which is used by the thyroid gland in the production of thyroid hormones.

For vegetarian children and women, the phytic acid in soy can have serious negative effects. Since iron is already moor poorly absorbed in plant based foods women and children who rely on soy products for their protein needs may experience anemia from insufficient iron. In women, iron is needed to replace the loss during their menses and in children iron is required for growth and development. This could also be a reason why iron is a nutrient of concern for vegetarian and vegans alike. 

Phytoestrogens

A more common concern of soy is it’s phytoestrogen properties which can mimic the effect of estrogen. Estrogen is a female hormone which by the way, is found in both male and females, so males are by no means exempted from this concern. Phytoestrogens are plant estrogens and have a similar structure to estrogen found in our bodies. Because of its similar structure, the overabundance of the phytoestrogens can create adverse effects in our human tissue. A study showed that drinking just two glasses of soy milk a day for one month has enough of these phytoestrogens to alter a woman's menstrual cycle. You may want to think twice about that soy latte next time. 

How to enjoy the benefits from soy

Soy prepared artisanally is full of nutrients. The best way to consume soy and enjoy its benefits is when it has been fermented. Fermented soy is found in miso, tempeh, and natto. These foods are in a class of its own in terms of nutrients - full of healthy bacteria, cholesterol lowering fibre, and rich in protein. Tofu prepared in its traditional ways is similar and the art of making tofu has been compared to that of making wine, with specific harvest seasons, grinding methods and even the natural material used in the tools used to strain and cook the beans over and over again.  This is certainly a far cry from our current mass produced tofu that we find in oru grocery stores and even wet markets. The Japanese’s care in these preparation methods also removed and neutralized the phytic acid found in the beans. 

If you look into the soy that is being used in your veggie burgers, the likelihood is that it hasn’t gone through such great care - otherwise, I doubt it would make it into your burger, as ‘gourmet’ as it could be. Because of our disconnect with our food, it’s now hard to know how our tofu is being prepared. So next time you choose to enjoy soy, opt for miso, tempeh or natto. Make a habit of reading the labels and ingredients of your ‘green’ choices on restaurant menus and supermarket shelves, soy is likely a hidden ingredient and while you’re reading you may find some other surprises that aren’t so healthy. The easiest switch is swapping your soy milk with oat, coconut or almond milk. Read a comparison on nut milks here

Below is a list of hidden sources of soy

  • Imitation meat. E.g. veggie burgers 
  • Imitation dairy e.g. vegan versions of mayo, cheese, yoghurt 
  • Soy sauce, teriyaki sauce, other asian sauces in particular 
  • Meal replacements and shakes 
  • Infant formula
  • Protein bars
  • Desserts, baked goods and baking mixes 
  • Prepared soups, broths and mixes 
  • Bread crumbs


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