Soya still divides opinion, despite countless of studies showing its safety. The scare-mongering stories based on horrific animal experiments and fuelled by vested interests are slow to die down but soya is certainly not the villain it was once portrayed to be.
Where did it come from?
The history of people consuming soya beans dates back to the 11th century BC in China. By the 15th-16th century, soya was introduced to many parts of Asia, including Japan and India, and in the 18th century soya cultivation started 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. Soya is now grown in many European countries and has effectively become a local and sustainable food crop.
Soya is a good source of protein and it contains all essential amino acids (protein building blocks) the human body needs. It is a good source of polyunsaturated fats (including the essential omega-3s), free of cholesterol and contains disease-busting antioxidants, B vitamins (including folate) and iron. Calcium-fortified soya products such as soya milk and tofu also provide significant amounts of this important mineral. And let’s not forget fibre – soya (edamame) beans and products made using the whole beans are a great source and that’s also why soya is good for bowel health.
Much of the critique and attacks on soya focus on phytoestrogens. So what is it about? Phytoestrogens are natural substances found in many fruits, vegetables, beans, peas and wholegrains. Isoflavones are the particular type of phytoestrogens found in soya 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 for that matter).
Scientific studies and reviews focusing only on human data conclude that isoflavones from soya foods are completely safe and don’t pose any health risks. 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 either. And studies looking into soya isoflavones and their possible effect on male hormones (testosterone) and reproductive functions concluded that there is absolutely 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 soya consumption can lead to altered sexual development or impaired fertility.
Scientists agree that soya can improve heart health – a fact supported by dozens of clinical trials. Soya consumption has been shown to reduce blood cholesterol levels and harmful plaques in the arteries, thus improving 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. And studies also suggest that isoflavones and soya protein composition work together to lower cholesterol and so reduce the risk of heart attack and stroke.
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 supplementing the diet with soya foods or soya isoflavones may reduce the frequency or severity of hot flushes and other menopausal symptoms.
The North American Menopause Society conducted a comprehensive review of research on soya and menopausal symptoms and concluded that soya isoflavones are effective in controlling hot flushes. However, as the overall diet has an effect on our health, making soya foods a part of a healthy diet is better than taking supplements!
Several studies from different countries suggest that regular soya intake during adolescence reduces breast cancer risk later in life and the risk continues to fall if people continue to eat soya as adults. This 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 cancer. 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 two glasses of soya milk) were less likely to die from the disease and had a significantly lower risk of recurrence. And the same results were found in other studies too!
Soya infant formula
Mothers who are unable to breast feed and can’t use donor milk have to use specially formulated milks to feed their baby. Soya-based infant formulas provide all the nutrients required by a growing infant. In the US, about a quarter of all formula-fed babies are given soya formula. A number of studies confirm that babies fed soya-based formulas grow and develop at a normal rate. Although breastfeeding is always superior to formulas, soya formula is a safe alternative.
Some people worry about phytate (phytic acid) in soya. It’s 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. Nothing to worry about!
Soya growing is indeed a serious problem – but not because of vegans! Around 75-80 per cent of the world’s soya production is fed to livestock – cows, pigs and chickens – so that people can eat meat, eggs and dairy foods. Much of it comes from the Amazon and other deforested lands. On the other hand, only around six per cent of soya beans are eaten directly as whole beans or in soya products like tofu, soya milk and soya sauce.
Most manufacturers using soya as an ingredient for human food products in the UK have a strict non-GM soya policy and many soya milk brands use soya grown in Europe. If you want to be sure, choose organic – no GM is one of the organic criteria.
Traditional soya foods such as soya sauce, tamari, miso, tempeh, tofu and soya milk were developed in Asia using the whole beans. That’s also the reason why these foods are healthier than foods based on soya protein isolates, which are extracts from soya beans and include textured vegetable protein (TVP) and other meat substitutes. However, soya-based mock meats still provide a valuable, low-fat source of good protein.
Soya beans are a versatile and healthy food which can be enjoyed and savoured as part of a balanced diet. Whether it’s edamame, miso soup, tofu stir-fry or a soya milk cappuccino – soya beans are a delightful way to add nutritious recipes to your culinary repertoire.