Published On: Wed, Jun 12th, 2019

The truth about soya: Revealing the science behind the gossip

We’ve all seen the headlines and for some of us, the health scares linked to soya have been salient enough to ditch the tofu altogether. But is it actually bad for us? Charlotte Willis reveals the science behind the gossip.

Ah, soya. Where would we be without you? Just the very thought of a tofu-less dinner plate, a soya-less sauce and a soy-free creamy latte is enough to leave many vegans at a culinary loss. But when headlines regarding the potential carcinogenic, hormone-disrupting health implications of soya reared their heads a few years ago, many of us were left confused over whether we should be eating things like tofu at all. 

The disparaging aftershocks of proclaiming ‘X causes Y’ in a national newspaper have never before been so strongly felt than when it comes to soya, with negative opinions influencing concerned consumers who ditched this protein-rich legume out of fear. Soya was rumoured to contribute towards the development of breast and ovarian cancer in women. In men, soya was deemed to have emasculating effects, counteracting testosterone levels and leading to breast development and poor muscle tone. 

Now we’ve well and truly visited the rumour mill, let’s continue by examining the scientific nature of soya. 

The Science

The soya bean (Glycine max) is an edible green, yellow or black bean which is grown in pods. The soya plant is native to China, where its consumption and cultivation dates back to the 11th century. Soya has been an integral part of Asian cuisine ever since – and for good reason. Soya has a dense protein content, containing all eight essential amino acids, and is a rich source of healthy polyunsaturated fats. 

The main health concerns surrounding the safety of soya stem from one particular component of the soya bean: the phytoestrogens. These are natural compounds found inside the bean, as well as other fruits, vegetables and wholegrains. A specific class of phytoestrogens, known as isoflavones, are found within soya. It is from here that people begin to take issue. We tend to hear the word ‘oestrogen’ associated with soya, and naturally assume that it has oestrogenic effects on the body – an assumption which is not necessarily true. 

The effect of oestrogen on the body is not clearly defined. Whilst it has a beneficial part to play in the health of certain tissues such as our bones, higher levels of oestrogen may result in negative effects in other tissues, such as the breast and reproductive tissues in some women. Ideally, the body requires a selective oestrogen modulation: this modulation compound responds positively in tissues where oestrogen is beneficial, and will suppress harmful effects in tissues where oestrogen is potentially negative to health. Now, I wonder where you can find such an oestrogen modulator?

Hormone Regulator

Soya is indeed an example of a selective oestrogenic modulator. Soya phytoestrogens have been scientifically proven to help lower the incidence of breast cancer (an anti-oestrogenic modulator) but can simultaneously, and significantly, increase the hormone regulation in post-menopausal women (a pro-oestrogenic effect). In fact, it has been found that phytoestrogens in soya have a balancing effect on the levels of natural oestrogen in the body – helping normalise low oestrogen levels in post-menopausal women and strengthening bone tissues to prevent osteoporosis. All the while, countering abnormally high blood oestrogen levels by binding to the hormone and blocking its absorption. It seems with soya, one size does not fit all! 

So what about those diagnosed with breast cancer? Overall, scientific researchers have demonstrated that those patients who were diagnosed with breast cancer, and subsequently ate the most soya in their diets, lived significantly longer with significantly lower re-occurrence rates of cancer. This survival improvement was true of both oestrogen responsive and oestrogen non-responsive tumours. 

Soyboys

I’ve lost count of the number of men I’ve spoken to who claim that they shouldn’t eat soya, as it makes them “less manly”. Sigh. 

If we look to the scientific evidence, there is absolutely no support to suggest that consuming a higher level of soya phytoestrogens results in poorer male sexual or hormonal health. This includes sperm count, sex hormone levels and male genital development. A study examining a high soya intake in men, of up to 70g of isolated protein per day, did not find any significant effect upon male sexual health nor testosterone levels. What’s more, eating more soya can help protect against prostate cancer in men. Far from the emasculating reality that some like to claim!

Setting the record straight

I hope you can see from the scientific evidence on human subjects cited above, that consuming soya has not been proven to have a detrimental effect upon the human body. Quite paradoxically, soya consumption has been linked more frequently to a higher level of health in both biological males and females than it has consequence. So the next time someone questions your edamame beans, you can be ready with the facts, to set the record straight! 

The dos and don’ts of soya

Whilst consuming soya is a healthy addition to your diet, as with any ingredient, there are healthy and less healthy ways to eat it. 

Do:

  • Buy Organic: The overwhelming majority of soya and soya products are genetically modified. Always opt to buy organic tofu and soya beans where possible.
  • Ferment Them: Fermenting soya beans (such as in Natto and Tempeh) is one of the healthier ways to eat soya, as the fermentation process releases health-affirming substances.
  • Drink Organic Soya Milk: Organic soya milk is a delicious, healthy and diverse way to get your fix of soya phytoestrogens. High in protein and free from saturated fats.

Don’t:

  • Eat Too Much Highly Processed Soya Protein: As much as we all love a soya burger or soya sausage, eating highly processed soya products is not something to be enjoyed regularly, as these often contain GMO soya and high levels of fat.
  • Consume Too Many Sweetened Soya Products: Due to the savoury nature of soya, manufacturers often add in a form of glucose syrup or sugar to their products. Read your labels carefully, and choose unsweetened products where possible.
  • Go for Deep Fried Soya: Again, some soya products are healthier than others. Deep fried tofu or soya beans are a definite once-in-a-blue-moon treat, and not to be enjoyed every day.  

Charlotte Willis

Charlotte is a freelance journalist and health writer who has worked with the Vegan Society and other online vegan publications. Her fields of expertise and interest include vegan nutrition, holistic healthcare, mindfulness and fitness. She is currently researching and studying the various links between food and psychological health while pursuing a doctorate degree in counselling.

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