Soy: it’s just a bean, not a bomb

By Kath Fourie

Plant-based eating is a growing global trend. As a primary element in many plant-based foods like tofu, tempeh, miso, soy milk and processed ready-made foods like veggie burgers, soy has become a pervasive ingredient in plant-based diets.

Yet it carries a stigma that bothers many new plant-based dieters. “Wait, doesn’t soy cause cancer? Someone told me that once!”

Hormonal association

So where does the confusion about an association with cancer come from, specifically hormone-related cancers?

This may sound like the start to a corny joke but it all began with an Australian farmer who, back in the 1940s, noticed fertility issues with his sheep that were eating a lot of clover.

Clover is rich in plant-derived chemicals called phytoestrogens, as is soy. Many other foods such as plums, pears, berries, cabbage and onions contain phytoestrogens, but not in the same concentrations as soy.

The phytoestrogen factor

Phytoestrogens have a similar shape to the human hormone of oestrogen, and the worry (80 years ago) was that consuming soy may lead to adverse health effects if eaten regularly or in large quantities (Davis C., 2019).

Fast-forward to today and we’re a long way down the road with testing and understanding soy and how it interacts with the human body.

There are four main classes of phytoestrogens in soy. The class most studied is isoflavones, which oestrogen receptors can receive in different types of cells in our bodies in the same way they receive human oestrogen.

Human cells have two types of oestrogen receptors – Alpha and Beta receptors. Plant-based phytoestrogens prefer to bind to the Beta receptor. In areas of the body that don’t have Beta receptors, isoflavones have minimal impact (Greger, 2016).

This is a good thing because they do really important work in those cells that human oestrogen may bypass. They can bind to Alpha receptors, but then they compete with your body’s natural oestrogen.

Updated thinking

Thankfully, you’d have to consume significantly wild amounts of soy to have enough isoflavones in your body to have a proper punch up with your natural oestrogen – I’m talking eating buckets of the stuff every day.

To get an idea of how isoflavones are viewed in 2021 and to understand the important work they do for you, leading gastroenterologist Dr Will Bulsiewicz states in his 2020 best-seller book Fiber Fueled that:

“isoflavones have a number of health benefits, including: lowering cholesterol, strengthening bones, treating menopausal symptoms, lowering risk of coronary heart disease, and reducing risk of prostate/colon/breast/ovarian cancers” (Bulsiewicz, 2020).

How much soy can I eat?

If you’re keen to eat soy, it’s recommended to go with soy-based foods that are not too highly refined.

Tempeh, miso, tofu, soy milk, tamari sauce and edamame beans are all ideal sources of soy protein as they are either fermented or cooked at high temperatures and are closest to their whole-food form (Bulsiewicz, 2020).

Tofu and tempeh are great sources of complete proteins too, with 150g of firm tofu delivering 12g protein (Dietetics Association of South Africa, 2019). That said, a few commercial soy burgers, sausages and faux meats here and there are not going to harm you.

What about those isoflavones? According to Dr Chana Davis of Fuelled By Science, it is commonly accepted that 3 to 4 servings of soy-based food per day is safe to eat, which would deliver around 100mg of isoflavones into the body.

Depending on what type of soy-based food you eat, 3 to 4 servings can deliver up to 48g of protein, which is 90% of the way to a recommended daily protein intake for an adult (Dietetics Association of South Africa, 2019).


Soy foods can be viewed as ubiquitously as chicken or beef in our modern diets. So, the next time you’re staring at the packages of tofu in the vegan section wondering how on earth you cook and eat it, grab one!

Within 60 seconds of Googling tofu recipes you will be amazed at how easy it is to transform it into a protein rich meal, and your gut will thank you for it.

About Kath Fourie

Kath Fourie is a plant-based food and health enthusiast who lives in Curry’s Post, just outside of Howick in KwaZulu-Natal. Kath’s interest in whole-food and plant-based food has expanded and developed over the last 8 years, which have been formative for her dealing with cancer and loss in her family. Part of her journey has been the development of FULLsome, which encompasses wholesome and fulfillment into a combo-concept! FULLsome wants to remove barriers to plant-based eating for everyone.

Author: Pedro van Gaalen

When he’s not writing about sport or health and fitness, Pedro is probably out training for his next marathon or ultra-marathon. He’s worked as a fitness professional and as a marketing and comms expert. He now combines his passions in his role as managing editor at Fitness magazine.

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