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ASK THE NUTRITIONIST: How healthy are soy products?

In this week's column, Nonie De Long features the first of the top 10 nutrition questions she is asked
Farmer Spraying Soy Plants
File photo shows farmer spraying soy plants with pesticides.

Dear readers, this week’s column features the first of the top 10 nutrition questions I get asked. Tune in over the following nine weeks for the remainder. If you are confused by conflicting nutrition advice or have lingering questions, this may help clear some of them up. If you don’t see your question answered, send me an email with your query, and if I can, I’ll feature it in an upcoming column.

One of the most common questions I get is about the health of soy products, often from those wishing to cut down on meat and find an alternate source of protein. I also get the question from women in menopause who are looking for ways to mitigate the hot flashes and sleep-related symptoms. It can be difficult to figure out the data around menopause and soy products. Additionally, with the soaring cost of groceries and concerns with the sustainability of meat consumption, soy as an alternative may be something on many people’s minds. So, let’s do a deep dive to better understand the facts about soy.

First, let’s do an overview. Soy is a legume containing all the essential amino acids and is readily available in a number of products so it stands to reason that people have an interest in it. In addition to protein, soy is rich in B vitamins, fibre, potassium and magnesium (if the soil contains it). If you aren’t aware, soy can be found as a milk alternative, tofu, tempeh, edamame beans, miso paste, meat alternative products (weiners, tofurky, burgers), vegetarian texturized proteins, soy sauce, many flavourings, and infant formulas. These are marketed heavily toward the vegetarian and health-conscious community and it’s an ever-growing market.

Soy for Menopause

Soy is particularly interesting as food for menopausal women since we know Japanese women consuming traditional diets rich in soy don’t experience the same menopausal symptoms that North American women do. It’s long been theorized that this is because of the isoflavones in soy. These phytoestrogens (plant estrogens) are weaker than human estrogen but can bind to estrogen sites in the body. This means they have the power to mimic and alter estrogen levels and responses in the body. In some studies, soy has been found to be effective in reducing menopausal hot flashes, without the risks associated with hormone replacement therapy. However, studies vary widely on this issue, depending on dosage and other variables. Some studies suggest it may be the protein in soy instead of the isoflavones that actually make the difference in outcomes. That would mean eating the whole food, rather than taking a supplement is best for those seeking menopausal relief from soy. This could account for why studies haven’t been consistent, as many have only looked for responses to supplemented isoflavones, not the consumption of the whole food.

When considering studies like this it can be difficult to extract clear data. Is it an animal or human study? What type of soy is used – whole food or food extracts, organically grown or GMO? What dose of these is given? Is it enough to be therapeutic? What are the hormone levels of study participants to begin with? What are the other lifestyle factors of study participants?

Even the theories we start with may be flawed. For example, do Japanese women experience fewer hot flashes due to their soy intake or due to other specific dietary and lifestyle habits, like their consumption of fermented foods and their lack of processed foods, for example? We know processed foods increase inflammation, which impacts menopausal symptoms, and we know fermented foods decrease inflammation and help modulate hormone responses in the body. How might all of these factors interact? These questions remain difficult to answer.

From Harvard’s School of Public Health: “There are many factors that make it difficult to construct blanket statements about the health effects of soy.”

The bottom line on soy in menopause: some women feel it makes a great difference to their menopausal symptoms, while others do not. I’m sorry the data isn’t more clear than that. It would seem that if you want to try it the best test would be using whole food products instead of processed products or supplements and taking a bit each day. A few months of intake is best to determine if it helps you. The best products to try are organic and non-GMO, fermented soy, which has additional benefits. I will get into the reasons for these recommendations below.

Soy and Cancers

Soy products have been maligned as causing cancers but I haven’t been able to find data to support those claims. In fact, soy products have been shown to reduce the incidence of breast cancers. “Several large, human studies—in which thousands of women have been followed for many years—consistently show that compared with women who do not eat soy, women who regularly eat soy have lower breast cancer risk. Some of these studies also suggest that breast cancer survivors who consume soy foods have a lower risk of breast cancer recurrence compared with survivors who avoid soy.” Soy has also been shown to be protective of bone health in cancer survivors in studies. Now, this could be because of the consumption of soy, or it could be because those who regularly consumed soy were also taking other lifestyle and dietary measures which reduced their risks of developing breast cancer. Nutrition studies are tricky. It would seem, in the least, that soy intake is associated with lower risks and that avoiding it is not beneficial.

Soy and Hormones

On the flip side, soy intake may lower sperm count and testosterone in males, but more studies are needed. Rodent studies suggest that eating large amounts of the estrogenic compounds (isoflavones) in soy reduces fertility in females and could trigger premature puberty. It’s been speculated that this could have to do with the spike humans have seen in these areas of pathology. There is no denying that our female children are reaching puberty earlier and fertility is a growing problem for many in developed countries. The data is not in yet on these related to soy.


Some nutrition experts advocate limiting soy products to those that are fermented to reduce the anti-nutrients present in the bean. I would agree with this recommendation. In Japanese culture, this is typically how soy products were prepared and consumed. Miso, natto, tempeh, and traditional soy sauces are all fermented products.

In case you’re not aware, beans all possess anti-nutrients. The anti-nutrients in soy act to block mineral absorption - especially zinc. And even if you don’t eat soy it’s hidden in many processed foods so the likelihood is that you’re being unintentionally exposed. However, fermentation releases the anti-nutrients and makes soy a super healthy food that not only has nutritive value but also improves the gut biome.

Soy for Men, Babies, Thyroid

It’s been shown that soy can have an estrogenic effect on males, hindering growth and in rare cases, contributing to gynecomastia (breast development). I don’t recommend it as a staple food for growing males for this reason.

In babies soy often creates allergies and nutritional problems, including sometimes very serious digestive issues. Soy consumption in children has been linked to an increase in Kawasaki disease, an autoimmune condition that causes inflammation in arteries and can result in irreversible and devastating damage to the heart. The hormonal impacts of soy on developing babies are yet unknown. I don’t recommend it as an optimal alternative to breast milk.

It’s widely debated that soy can impact thyroid health with studies aplenty to debunk this. But the studies repeatedly conclude that where iodine is sufficient, soy doesn’t interfere with thyroid function. Clinically I have regularly seen regular soy intake correlated to the development of thyroid issues. Given that experts feel almost everyone in North America is deficient in iodine and that in Japanese culture a diet high in iodine diet was paired with soy intake, it might not be wise for everyone to increase their intake of soy without first looking at their iodine levels. Thyroid disease is rampant in North America today and often undiagnosed until it’s extremely far gone. It has an incredible impact on overall health and wellness.


Could some of the problems with soy also have to do with how the crop is cultivated today?

Soy is the number one genetically modified crop in the world. In 2018, GMO soybeans made up 94 per cent of soybeans planted in the U.S. GM crops are grown around the world by approximately 17 million farmers. Most of them are in developing countries.

In total, more than 70 countries import or grow GMOs. According to ISAAA, the top five countries growing GMOs in terms of crop area as of 2019 are the United States, Brazil, Argentina, Canada and India.

The rationale is that genetic modification of organisms improves the yield and nutrient content of the products. It’s also promoted to reduce costs and reduce the need for pesticides. According to one Berkely biotech specialist, “numerous studies have shown no nutritional differences between commercially available GMO and non-GMO foods. She continues, “genetic modification can improve the nutritional content of some foods, for example, low linoleic acid canola oil that can reduce trans-fat content.” As an aside, if you follow my work regularly you already know that using natural fats reduces trans-fat content to zero without the use of genetic modification.

Forbes reported in 2013 that the adoption of GM technology did not result in less herbicide use, but more. In a paper prepared for presentation for the 2015 Agricultural & Applied Economics Association and Western Agricultural Economics Association Annual Meeting, in San Francisco, CA, July 26-28, Purdue University researchers shared that “if all American farmers switch to growing non-GMO crops, food will cost more, crop yields will be lower and more land will be needed to grow our food.” The paper was summarily disregarded and fact-checked into oblivion.

We, humans, like to think our technology can improve all systems, but things like soil biome health and the health of the surrounding ecology in light of massive clear-cutting and mono-cropping such as is employed in GM agriculture are not factored into our equations. Time will teach us if this is a good system or not.

Social/Economic Impact

In India, where GM crops were sold en masse to small farmers as a way to drastically increase yield and salary, more than 296,400 have committed suicide. By 2008 the number had soared to over 1,000 farmers per month. PR reps for the related stakeholders have done much to shift the blame to the small farmers whose lives have been destroyed, but independent and unbiased journalists and humanitarian organizations who have travelled to the region have confirmed the relationship between GM crop failures and debt. Prince Charles spoke out about it, branding it “GM Genocide” and saying “it had become a 'global moral question' – and the time had come to end its unstoppable march.” Vandana Shiva, physicist and ecologist and world-renowned environmental leader, who has seen the devastation in her native India with her own eyes, has been speaking out about this publicly and through her books and non-profit work for some time. You can hear one such interview here. Her documentary also touches on it.

You may ask, what does the health of soy products have to do with the cultivation of soy products? But everything is connected. We cannot dump pesticides on our land without them ending up in our tap water. We cannot expect these pesticides don’t alter the microbiome of the soil in a profound way and that an altered soil biome won’t impact us. We can’t expect it to not impact our pollinators and that that won’t impact us.

Sure, for a time, soil treated thus may produce bountiful crops, but over time it remains to be seen what can be grown when soil is too far gone to be bolstered with liquid fertilizer. Is it sustainable to repeatedly till and spray the soil with ever stronger liquid fertilizers and pesticides? Can this produce foods as sweet and nutritionally dense as the natural systems it replaces? In answer, I invite you to try a GM tomato alongside a homegrown one using organic soil and growing methods and weigh in. What do your taste buds tell you? Blindfold the kids, line them up and try it – a simple and fun home experiment my father liked with homegrown food when I was a kid. I also invite you to place a sample from both homegrown and GM tomato crops on your counter and watch what happens. In my home, the GM tomato will deteriorate much more quickly than the garden-grown one. I invite you to determine if there is a difference for yourself.

The takeaway on soy is that it can be healthy if it’s organic, non-GMO, and fermented and there is sufficient iodine intake. It may not be healthy or advisable for men, and I certainly can’t recommend it without further study as an optimal staple food for infants and children.

I hope this is helpful. Tune in next week for the lowdown on red meat. As always, if you have a question for the column, you can write to me at [email protected]. If you want to sign up for a class or know more about what I do, you can find me online at


Nonie Nutritionist