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Soy has been a favourite staple of plant-based eaters for decades. Nutritionally, soy packs a powerful punch: more protein than most other legumes, ample fibre, omega 3 fatty-acids, calcium and iron. Contains all 11 of the essential amino acids and supplies health-promoting phytonutrients like isoflavones that reduce cholesterol levels and cancer risk.

As a bean, soy can be eaten from the pod once cooked, fermented into miso paste and tempeh, curdled into tofu or processed into milk or various other products. As an ingredient, processed soy is found in hundreds of processed food products on the market today, including faux meats and baby formulas. It’s available as hydrolysed and textured vegetable protein, soy lecithin, soy flour, isolated soy protein, de-fatted soy flour and soy protein concentrates.

image of a soy field

Despite its many applications within the food chain, controversy rages when it comes to soy. Its wealth of nutrients and potential health claims have intensified an explosion of studies, especially when detailing its ability to lower cancer risk or promote its growth. This confusion surrounds a class of phytonutrients called ‘isoflavones’ which have a similar structure to oestrogen, which is why they are referred to as phytoestrogens.

Phytoestrogens, despite their name, actually work differently in the body compared to human oestrogen and appear to exert healthful effects. Consuming isoflavones during early childhood and adolescence has been shown to reduce lifetime risk of breast cancer. Furthermore, soy consumption may reduce the risk of breast cancer occurrence and improve survival from breast cancer. Studies where populations with diets high in soy protein and low in animal protein have shown lower risks of prostate and breast cancers than other populations.

The media have propagated concerns about soy’s effect on hormones. You may have heard how soy consumption decreases or interferes with male and female fertility or gives a male ‘man-boobs’. But no solid evidence supports these assertions.

Similarly, fears circulated that soy-based infant formulas led to problems with sexual development, brain function and immunity and future reproduction. No conclusive evidence supports these claims either.

Another soy concern is its possible interference with thyroid function. Soy has been reported to cause ‘goitres’; hypothyroidism. But studies have shown that an adequate intake of iodine reverses any goitre-causing effect of soy in a healthy person. Soy foods have also been reported to interfere with the absorption of hypothyroid medication, but soy can still be consumed with medication adjustments. Additionally, population studies have shown a protective effect of soy on thyroid cancer.

Essentially, soy foods are not only safe for everyone (except for those with an allergy, of course!) they are nutrient-dense foods that may provide additional health benefits. Overall, soy is well tolerated, and because it is a complete source of protein shown to lower cholesterol, it is recommended as a dietary substitution for higher-fat animal products. Moreover, increasing dietary whole soy protein lowers levels of total cholesterol, low-density lipoproteins, and triglycerides; may improve menopausal hot flashes; and may help maintain bone density and decrease fractures in postmenopausal women. There are not enough data to make recommendations concerning soy intake in women with a history of breast cancer. The refined soy isoflavone components, when given as supplements, have not yielded the same results as increasing dietary whole soy protein. Thus, following these dietary guidelines is the best way to make sure your body gets the benefits of soy products.

To enjoy soy foods as part of a balanced plant-based diet, do the following:

  • Consume soy from organic, whole-foods or minimally processed sources such as soybeans, tofu, tempeh, miso, soybean sprouts and organic soymilk.
  • Use soy in moderation – approximately 1 cup of soy milk or ½ cup soybeans, tofu or tempeh per day.
  • Minimise the use or avoid processed, non-organic soy products, like soy protein isolates found in protein drinks and bars, faux meat products such as quorn, cereals, meal replacement shakes and other processed items.

BUT WAIT! IT GETS EVEN MORE SOY CONFUSING

We may have established soy’s health benefits, but soy’s story doesn’t end there unfortunately. To truly understand the full picture of soy products within our food chain we need to shed light on its growing conditions which ultimately weighs in on your decision whether to include soy in your diet or not.

93% of soy grown today in the US is genetically modified. It trumps both corn and cotton grown that is genetically modified, meaning its DNA has been altered in a laboratory to incorporate genes from other plants, animals, viruses or bacteria, which ultimately means the seeds, become resistant to herbicides and pesticides used in the growing process. In very simple terms the crops can be sprayed but not ‘harmed or killed’ like the weeds growing around them are by the herbicide or pesticide. Clever farming technique you may say, but these herbicides and pesticides are known to be harmful to humans.

image of organic vegetables

A study published in the Journal of Agricultural Sciences has shown that genetic modification of the soybean causes significant disruptions to the levels of formaldehyde, a known carcinogen, and glutathione, an important antioxidant necessary for cellular detoxification. Formaldehyde is a known class 1 carcinogen. Meaning it’s likely to cause cancer. Glutathione on the other hand, is a potent natural antioxidant important in detoxifying processes of the body. The study found that the amount of glutathione was significantly reduced in the GMO soybeans, showing that not only does it increase our exposure to carcinogens, but reduces our intake of the helpful substances that help our body fight disease and the toxins that make us ill.

So while soy may be healthful to humans, I recommend only sourcing non GMO-soy, meaning all your soy products within your home should be certified organic. There simply is no other way around it.

Furthermore, if you are an omnivore then it’s worth noting that over 85% of the GMO-soy grown today is fed as a protein rich feed to livestock. Thus if you are not buying organic eggs, poultry and meat products you will via proxy also be consuming GMO-soy found in the flesh and eggs of these animal products.

The bottom line:

ALWAYS buy non GMO-soy by buying certified organic soy and other animal products.



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