WHY IS SOYA CONTROVERSIAL?
Soya is one of the world’s most commonly grown crops and is widely consumed in a huge number of forms throughout the world. It is classified as an oilseed in that it contains larger quantities of oil than cereals such as maize and wheat and also contains a high percentage of protein. In terms of its fundamental nutritional composition, it is probably one of the most desirable products to use as a component of our diet and yet questions are continuously asked about its acceptability as a food and its safety. Let’s try and address some of these questions.
What is so special about soya as a food?
It has a very particular composition in that it contains large quantities of fat and protein, and the types of fat and protein found in soya are particularly desirable ones in terms of their composition and nutritional value. The consumption of soya protein can reduce blood cholesterol levels and reduce the risk of coronary heart disease. Furthermore it contains a number of other substances that can be beneficial to our health and it can easily be incorporated into a wide range of different foods.
What does soya look like?
Soya is grown as soya beans which are small spherical beans with a loose outer coating and a hard centre. When newly harvested, they are green in colour but on storage and drying they become a pale and creamy brown in colour.
Can I eat whole soya beans ‘as is’?
Not recommended as they taste very unpleasant when raw! However they can be processed into a huge variety of products which can then be added to our food. In this respect soya is not really any different from many other crops – would you eat raw maize kernels?
So what types of soya products can I eat?
Soya can be ground into flour, which is then used in applications such as bread and other baked products. Alternatively it can be converted into products such as soy milk and tofu. Another common process is to remove most of the fat from the beans to give the oil (which is used in cooking oils and to make products such as margarine) and what we call defatted soya flour, which is very high in protein and can itself be used in food or converted into products such as textured vegetable protein which is a meat substitute. Defatted soya flour can also be processed further to give products such as soya concentrate and soya isolate where the protein is even more concentrated and these are used to boost the protein content of foods and in processed meat products where they help to provide texture and stability to the finished products. Some soya milks are also made from soya isolate.
So, if soya is so marvellous, why do I hear all these stories about it being bad for me and even dangerous?
There are a lot of negative stories circulated about soya. It is important to understand that many of these stories relate to its status before processing and, as explained above, we should never eat raw soya. Other stories relate to issues which are specific only to certain types of soya products and to their consumption by certain types of people but scare-mongering stories abound which suggest that these issues are applicable to every type of soya and everyone who consumes soya. These stories are often simply not true but let’s look at some of the real issues.
What is bad about raw soya?
First of all it tastes nasty! This is primarily because it contains substances that cause the oil in the soya beans to deteriorate and produce unpleasant flavours that need to be removed by further processing. Then it contains certain other substances known as anti-nutritional factors which have a negative effect not only on the nutritional quality of the soya itself but also on other foods. The good news is that these are largely removed during the various steps used to process soya beans. This means that raw soya beans that have been processed using heat (e.g. roasting) or a combination of heat and moisture (such as the process used to make certain types of soy milk) will not only taste much better but will have more acceptable nutritional characteristics. Even when raw soya beans are simply ground to make soya flour, the flour is then used in processes such as baking which have exactly the same effect in terms of improved flavour and reduction of anti-nutritional factors.
I’m still not convinced. Tell me more about these anti-nutritional factors!
There are a couple of these that are particularly important:
Phytic acid is a substance which is naturally occurring in many cereals and oilseeds. It has a chemical structure which has the effect of reducing the body’s ability to absorb essential minerals such as calcium, iron and zinc. It is important to remember that soya is certainly not unique in containing phytic acid and that certain types of maize and sunflower seeds for example contain more phytic acid than soya, so any suggestion that soya is a particular villain in this respect is simply not true. That said, a number of the processes used to produce soya products from the raw beans will reduce (but not necessarily remove) the levels of phytic acid in the soya. Moderate consumption of soya products will not cause any significant problems with mineral absorption, unless the person consuming it is already deficient in certain essential minerals, in which they need to watch their intake of all foods containing phytic acid and not just soya!
Trypsin inhibitor is a substance found in raw soya beans that reduces the activity of the enzyme trypsin in our bodies. Trypsin is an important component of the digestive process as it breaks down protein into components that can easily be absorbed in our digestive systems, hence the presence of trypsin inhibitor in our food is undesirable. However trypsin inhibitor is sensitive to heat and moisture hence processes such as soya milk and tofu production or baking of products containing soy flour and water will remove most if not all of it. Trypsin inhibitor will only be a problem if you consume large amounts of raw soya beans or raw soya flour. Incidentally it is also found in a number of other substances including egg white and blood plasma.
I’m a woman who is going through the menopause. I’m very confused about eating soya because I hear good and bad stories – what is this all about?
The situation in regard to soya consumption by menopausal and post-menopausal women is very complicated and it is not surprising that you are confused. The reality is that soya contains substances called isoflavones which are chemically similar to the hormone called estrogen. Estrogen has a number of different effects in menopausal and post-menopausal women and consumption of isoflavones will cause some of the same effects. They can reduce the occurrence of hot flushes, reduce LDL cholesterol levels in the blood and may in some cases help to maintain bone density. On the downside, women who are deficient in iodine may experience problems with thyroid function if they consume large amounts of isoflavones. So it is a bit of a mixture of pros and cons - women in your situation should certainly get advice from your doctor before increasing your intake of soya.
Can I give soya based infant formula to my baby?
You should only use a soya based formula if you are unable to breast feed and your baby cannot consume cow’s milk based formula due to allergies or other medical reasons. Soya based formula is very safe and has been through an extensive level of processing aimed at reducing the quantities of anti-nutrient factors and other undesirable substances to very low levels but you should not use it to replace breast feeding or milk based formula unless there are very good medical reasons to do so. Always consult your doctor, clinic or a dietician specialising in infant feeding before making changes to your baby’s food.
I hear a lot of soya is genetically modified. Why should I consume this and is it safe?
There is probably more miscommunication and unsubstantiated scare-mongering about genetically modified (GM) crops and the foods derived from them than about any other aspect of the food we eat. A significant proportion of the soya grown globally is indeed grown from GM seed which has been developed to improve crop yields by enabling specialised herbicides with improved environmental properties to be used in soya growing areas. This has significantly reduced the cost of the soya and provided huge benefits for farmers. The GM soya has been very extensively tested and has been found to be no different from conventional soya in terms of its safety and nutritional properties, although it is interesting to know that the next development is GM soya which has a more desirable type of fat than conventional soya, thus providing a nutritional benefit for the consumer rather than just the farmer. There is certainly a lot of opposition to GM crops from activist groups but much of this opposition is now based on concerns such as the commercial status of GM seed and its suppliers rather than safety issues, as it is universally acknowledged by government bodies throughout the world that all types of GM soya grown globally are completely safe and indistinguishable from non-GM soya.
I think I may be allergic to soya. What should I do?
Soya contains a lot of protein and most food allergies result from the body’s adverse response to particular proteins so it is certainly possible to have a soya allergy but beware of self-diagnosis! First of all, see your doctor and have yourself tested for soya allergy to establish if you really do have a problem. If it is confirmed then you should obviously not consume soya in any form and should check the labels of processed foods to see if they contain any soya based ingredients or contact the manufacturer and ask them for some information. Be careful of ingredients such as lecithin which are often derived from soya but are not always declared as such.
So should I really be concerned about eating soya?
The name of the game is MODERATION, as is really the case for all foods. Soya is a highly desirable food with great nutritional properties and, unless you have a particular medical condition which requires you to limit your intake of soya products, you can consume moderate quantities of soya products as part of a balanced diet with full confidence that they are entirely safe and are probably beneficial to your health. Only a very small number of persons with specific problems in regard to soya consumption (for example menopausal women with iodine deficiency or persons with soya allergies) need to significantly limit their consumption or avoid consuming soya.