Is soya good or bad for you? Here’s what the experts say about soy

No other plant food divides opinion like soya – some champion its health and nutritional benefits, others say it should be avoided at all costs.

In reality, soya is a great all-rounder that packs a great nutritional punch and offers a range of health benefits.

So why is there so much scaremongering surrounding this humble bean and is there actually any truth to them?

We asked three health experts to give us the facts about soya and uncover the truth about whether is soya good for you…

What is soya?

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.

By the 15th-16th century, soya was introduced to many parts of Asia, including Japan and India, and in the 18th century the beans started to be grown in the USA.

Since then, it has become an important part of the diets of many populations and found popularity with vegetarians and vegans because of its versatility, nutrients and health benefits.

As Dr Justine Butler explains, many traditional foods such as soya milk, tofu, tempeh, miso, soya sauce and tamari that were developed in Asia use traditional fermentation or precipitation methods.

Many of these use the whole bean and are healthier than foods based on soya protein isolates. To extract protein from soya, the beans are heavily processed and lose some nutrients along the way.

Meat substitutes based on soya protein isolate, or textured vegetable protein (TVP), still provide a low-fat source of good protein, but are not as healthy as tofu or tempeh.

The nutritional value of soya

Soya is a good source of vegan protein as it contains all eight essential amino acids (protein building blocks) that the human body needs. It is also a rich source of polyunsaturated fats (including the essential Omega-3s) and is cholesterol-free.

On top of that, it contains disease-busting antioxidants¹, B vitamins (including folate) and iron. Calcium-fortified soy products, such as soy milk and tofu, also provide significant amounts of this important mineral.

Soya (edamame) beans and products like tempeh, made using the whole bean, are a good source of fibre, which is important for maintaining bowel health and can lower cholesterol².

Why is soya good for you?

Soya protein can also lower cholesterol levels and therefore is good for your heart health.

Soya may also help combat menopausal symptoms, with early studies in Japan finding that women who consumed the most soya had fewer hot flushes compared to those consuming the least.

Many other studies now show that the regular consumption of soya can reduce the frequency and severity of hot flushes and may help reduce other menopausal symptoms too³.

Additionally, scientists agree that soya can improve heart health – a fact supported by dozens of controlled clinical trials⁴. Soya consumption has been shown to reduce cholesterol levels and reduce plaque build-up in the arteries, which helps improve healthy blood flow.

One of the ways in which soya protein helps prevent or treat heart disease is that it interferes with cholesterol synthesis in the liver. Studies also suggest that isoflavones and soya protein composition work together to lower cholesterol and so reduce the risk of heart attacks and strokes⁵.

Does eating soy affect your hormones?

One of the most common criticisms surrounding soya is the impact it has on both male and female hormones, but do they really impact our hormonal health?

According to health researcher Veronika Charvatova, several studies from different countries suggest that regular soya intake during adolescence reduces the risk of breast cancer ⁶ later in life and the risk continues to fall if people continue to eat soy as adults.

The protective effect of soya was recently shown to apply to women who have breast cancer too. The Shanghai Breast Cancer Survival Study looked at over 5,000 women previously diagnosed with breast cancer⁷.

Results showed that those who ate more soya foods (11 grams of soya protein per day, equivalent to one and a half servings of tofu or soy milk) were less likely to die from the disease and had a significantly lower risk of recurrence. The same results were replicated in other studies⁸.

Dr Justine explains, “soya contains phytoestrogens, natural substances also found in many fruits, vegetables, beans, peas and whole grains. Their chemical structure is similar, but not identical, to the oestrogen found in animals, including humans.

“However, they are 100 to 100,000 times weaker and therefore have very little oestrogenic effect, if any. They may even normalise oestrogen signals in people with high levels of this hormone by binding to and blocking the receptor. Studies on humans concur that phytoestrogens from soya foods are completely safe⁹.

“In fact, men may even benefit from eating more as studies suggest that soya consumption is linked to a lower risk of prostate cancer¹⁰. And let’s not forget, cow’s milk and dairy products contain actual oestrogen!”

What are phytoestrogens?

Much of the critique and attacks on soy focus around phytoestrogens. So what is it about? Phytoestrogens are natural substances found in many fruits, vegetables, dried beans, peas, and whole grains.

Isoflavones are the particular type of phytoestrogens found in the beans. The chemical structure of phytoestrogens is similar, but not identical to, human oestrogen. In fact, phytoestrogens are estimated to be between 100 and 100,000 times weaker than the oestrogens that occur naturally in humans (or in cow’s milk).

Scientific studies and reviews focusing purely on human data conclude that isoflavones from soy foods are completely safe and don’t pose any health risks¹¹.

The concerns are based on animal experiments, which are irrelevant because not only do phytoestrogens behave differently in different species but also many of the animal experiments were based on injecting animals with high doses of isolated isoflavones or force-feeding them extreme amounts – that bears little relevance to human health.

Research examining the effect of soya-based infant formula on sexual development and fertility found no evidence of adverse effects on either¹². And studies looking into soya isoflavones and their possible effect on male hormones and reproductive functions concluded that there is no basis for concern.

The UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment conducted an in-depth analysis of soy effects on human health and acknowledged that there is no evidence that populations which regularly eat high quantities of soya have altered sexual development or impaired fertility.

Is soy bad for the environment?

One argument many people make when criticising vegan diets is to point out that soy production is damaging to the environment thanks to greenhouse gas productions and deforestation.

Soya growing is indeed a serious problem – but not because of vegans. It is because of meat eaters! Nearly 80% per cent of the world’s soya production is fed to livestock¹³ – cows, pigs and chickens – so that people can eat meat and dairy foods.

Much of it comes from the Amazon. On the other hand, only around six per cent of the beans are eaten directly as whole beans or in soy products like tofu, soy milk and soy sauce.

Most manufacturers using soy as an ingredient for human food products in the UK have a strict non-GM soy policy. They also do not use beans grown in the Amazon or other rainforest land. If you want to be sure, choose organic – no GM is one of the organic criteria.

“When the US began running out of suitable land for expansion, soya began its long march into South America. Currently around 80 per cent of global production (270 million tonnes per year) comes from just three countries – the US, Brazil and Argentina,” explains Dr Justine.

“It is big business, but not for human consumption, as most of this soya is grown for animal feed. The relentless expansion of soya production is an environmental disaster – but it’s not because of vegans!

“More than 70 per cent of the world’s soya production is fed to livestock – cows, pigs and chickens – so that people can eat meat, dairy and eggs. Most of it comes from the Amazon and other places facing environmental destruction, with only around six per cent of global soya production being eaten by humans.

“Many of the soya foods consumed in the UK are made with organic beans sourced from Europe and the US, unlike the genetically modified types grown for animal feed. If you want to see less destruction of the rainforest, switch to a vegan diet and eat more soya!”

Quick facts about soya

The Vegan Society’s resident dietitian Heather Russell believes it’s ‘a shame’ that so many people scaremonger when it comes to soya.

According to her, “it’s a valuable source of nutrition, particularly if you avoid animal products.”

The truth is that soya-based foods can be enjoyed by people of all ages, and may even provide some health benefits. Here are some facts about soya that will show you why it’s a great ingredient to enjoy as part of a healthy plant-based diet.

1. The soya bean has a special nutritional profile

Soya beans contain protein that is of a similar quality to the protein in meat and dairy. They have a higher fat content than other beans – mainly heart-friendly unsaturated fat.

2. Soya is great for people with higher protein needs

Unlike other varieties of plant milk, the quantity and quality of protein in soya milk is similar to cows’ milk. Young children, athletic individuals and people over 65 have higher protein needs, so it’s important that all their meals contain good sources.

Including soya beans, soya milk and yoghurt, tofu and soya mince helps to ensure that a vegan diet is rich in high quality plant protein.

3. Some soya foods are rich sources of calcium

Did you know that calcium-set tofu is one of the richest plant-based sources of calcium? You can work out whether or not it’s the calcium-set variety by looking for calcium in the list of ingredients.

Just 70g (2½oz) (uncooked weight) provides about a third of the daily calcium target set for adults in the UK – that might equate to less than a quarter of a block! Soya and linseed bread fortified with extra calcium and fortified soya milk and yoghurt are also really rich in calcium.

4. Eating soya protein may be positive for heart health

Some dietary approaches to lowering cholesterol promote the consumption of soya protein, because research suggests soya-based foods can help with cholesterol management as part of a balanced diet low in saturated fat.

5. A balanced diet containing soya is safe for reproductive health

Some people say that soya is a danger to reproductive health. The reality is that phytoestrogens in soya-based foods and others do not affect our bodies in the same way as the sex hormone oestrogen.

For anyone experiencing menopausal symptoms, research suggests that eating soya may help reduce the severity of hot flushes.

It’s a controversial topic that divides many, but can vegans eat honey? 

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References

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2. Ramdath DD, Padhi EM, Sarfaraz S, Renwick S, Duncan AM. (2017) Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease. Nutrients. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409663/
3. Ahsan M, Mallick AK. (2017) The Effect of Soy Isoflavones on the Menopause Rating Scale Scoring in Perimenopausal and Postmenopausal Women: A Pilot Study. J Clin Diagn Res. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5713750/
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