By Veronika Powell MSc, Viva! Health
No other plant seems to divide opinion like soya. Whilst some consider it a healthy and amazingly versatile crop, others warn against adverse effects and avoid it at all costs. So why are there so many myths surrounding soya and where do they come from?
A bit of history
Soya is a pulse native to Asia and historical records show that Chinese people have been consuming soya beans since the 11th century BC. It was gradually introduced to other parts of Asia and in the 18th century brought to the USA and successfully cultivated thanks to its suitable climate. Soya is now also grown in Europe and it seems nothing can hinder its popularity.
Soya is a good source of protein as it contains all the essential amino acids (protein building
blocks) that the human body needs and provides more protein than other pulses. It is also a good source of polyunsaturated ‘good’ fats (including omega-3 and -6), disease-busting antioxidants, B vitamins and iron. Calcium-fortified soya products, such as soya milk, yoghurts and tofu, provide significant amounts of this important mineral. Soya (edamame) beans and products made using the whole beans are a good source of fibre, important for good bowel health and can also lower cholesterol.
Claim: Soya can mess with your hormones
TRUTH: Soya contains phytoestrogens, which is why some people think it’s dangerous. Phytoestrogens are natural substances found in many fruits, vegetables, dried beans, peas and wholegrains. 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 found naturally in humans (and particularly in cow’s milk) and therefore have a very weak, if any, effect.
Scientific studies focusing purely on human data conclude that phytoestrogens from soya foods are completely safe and don’t pose any health risks. The concerns that have been expressed are based on animal experiments, which are irrelevant because phytoestrogens behave differently in different species but also many of the animal experiments were based on injecting animals with extremely high doses or force-feeding them excessive amounts — and this has little relevance to human health.
Research on the effect soya-based infant formula might have on sexual development and fertility found no adverse effects on either. The most reassuring fact about soya infant formula comes from the US where tens of millions of babies have been fed it over the past 40 years and there have been no reported ill effects.
Studies looking into soya phytoestrogens and their possible effect on male hormones and reproductive functions also conclude 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 soya 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.
Claim: Breast cancer patients should avoid soya
TRUTH: Human studies have shown time and again that regular, moderate soya consumption can not only lower your risk of breast cancer but also lower the risk of breast cancer recurrence in women who have had it. Other research looking at the safety of soya for cancer patients is also reassuring and suggests that soya consumption is either neutral (safe) or can even improve treatment outcomes! The amount consumed in some of these studies that showed protective effects was around 11 grams of soya protein per day — equivalent to one and a half servings of tofu or soya milk.
Claim: Soya supplements can lower cholesterol
TRUTH: Soya certainly can lower your bad cholesterol levels and is good for your heart. However, soya supplements added to an unhealthy diet can’t perform miracles! Scientists agree that soya can improve cardiovascular health by reducing cholesterol levels and plaque build-up in the arteries, which helps to improve blood flow. How? Soya protein can reduce your liver’s production of cholesterol whilst soya phytosterols compete with cholesterol molecules already in your blood and thus lower your cholesterol levels. And don’t forget, by eating soya, you’re probably replacing something far less healthy — a third beneficial effect.
Claim: Soya can relieve menopausal symptoms
TRUTH: Correct! It was discovered that Japanese women who consumed the most soya foods had less than half the number of hot flushes compared to women consuming the least. There are now many studies showing that regular consumption of soya foods or supplements can reduce the frequency or severity of hot flushes and certain other menopausal symptoms. The North American Menopause Society conducted a comprehensive review of research on soya and menopausal symptoms and concluded that soya isoflavones (the particular type of phytoestrogens in soya) are effective in controlling hot flushes. However, as the overall diet has an effect on our health, making soya foods a part of your diet is better than taking supplements.
Claim: Soya contains anti-nutrients
TRUTH: This usually refers to phytate (phytic acid), an antioxidant found naturally in pulses, wholegrains, nuts and seeds. It has several health-protective properties but critics have focused on its ability to bind to, and reduce absorption of, some minerals such as iron and zinc. The truth is, soaking, cooking and fermenting reduces phytate content and soya is always consumed when cooked and often fermented too so the effect of phytates is negligible.
Claim: Soya is destroying the planet
TRUTH: There’s no doubt that the massive scale of soya production is a serious problem — but not because of vegans. More than 80 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. And it’s almost exclusively soya from the Amazon and other places facing environmental destruction that is destined for livestock feed.
Only around six per cent of global soya production is eaten directly as whole beans or in soya products such as tofu, soya milk and soya sauce.
Most manufacturers using soya for human food products in the UK have a strict non-GM policy and don’t use beans grown in the Amazon or other vulnerable lands. If you want to avoid GM soya, choose organic.
Claim: There are good and bad soya products
TRUTH: Traditional foods such as soya milk, tofu, tempeh, miso, soya sauce and tamari were developed in Asia using traditional fermentation or precipitation methods. Many of these foods use the whole bean and are healthier than foods based on soya protein isolates. To extract protein from soya, the beans have to be heavily processed and some nutrients are lost along the way. Meat substitutes based on soya protein isolate or textured vegetable protein (TVP) — essentially the same thing — still provide a low-fat source of good protein but are not as healthy as tofu or tempeh.
When it comes to fermentation, there’s no easy answer. Some people digest fermented soya foods better than others. Fermented products come with friendly bacteria that can improve your digestive health but if you have a healthy diet, you have plenty of good bacteria in your gut already so you may not need more.
In summary, all the concerns about soya are based on animal studies, whereas more accurate human research entirely supports the overall safety of soya foods and their positive contribution to human health.
• For more information on soya, health and nutrition and for references in this article, please go to www.vivahealth.org.uk/soya.
• Viva!Health is a part of the charity Viva!, Europe’s largest vegan campaign group. We monitor scientific research linking diet to health and provide accurate information on which you can make informed choices about the food you eat — www.vivahealth.org.uk.