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OVERVIEW OF THE NUTRITIONAL BENEFITS OF SOYA
What is good nutrition? This is not an easy question to answer in a few words as we are inherently different as individuals and have different needs in order to achieve optimum health and quality of life. However certain fundamental principles of nutrition are applicable to us all, namely the need to consume adequate quantities of both what we call macronutrients (i.e. the ‘big volume’ nutrients such as carbohydrate, protein, fat and fibre) and what we call micronutrients (i.e. the ‘small volume’ nutrients such as vitamins and minerals that we only need in small quantities but which are essential for maintaining our body functions). Adding further complexity is the fact that the macronutrients are in turn sub-divided into those which are particularly desirable such as complex carbohydrates and polyunsaturated fat and those for which we need to control our intake such as simple carbohydrates and saturated fat. Furthermore we need to limit our intake of minerals such as sodium and for some vitamins such as Vitamin D, excessive intake can be dangerous. It all adds up to complex equation and it is not surprising that the public sometimes feels totally confused!
Clearly one solution to the problem would be to find a food or foods which magically provide all the nutrients we need in the correct quantities and provide us with a ‘one stop shop’ answer. The reality alas is that the nutritional characteristics of foods differ so hugely that this is unfortunately not going to happen. However there is no doubt that certain foods, both individual agricultural commodities and processed foods, do have particularly good overall nutritional characteristics and a diet containing significant quantities of these will certainly be beneficial.
Soya is probably the major agricultural crop with the best nutritional characteristics. We must remember that it is classified not as a cereal but rather as an oilseed, in that it contains significant quantities (around 20% of the soya bean) of fat unlike cereals which typically only contain small quantities of fat (typically around 5%) in their germ or seed. Soya also contains a large quantity (around 40% of the soya bean) of protein and in this respect it also differs from cereals whose main constituents are carbohydrates. Soya thus differs considerably from cereals such as maize and wheat in its nutritional composition and is a convenient source of protein and fat derived from plants rather than the more expensive animal sources such as meat and milk.
We should also remember that we need suitable amounts of carbohydrate in our diets, particularly complex carbohydrates. Can soya also provide these and thus deliver an optimum ‘cocktail’ of macronutrients? The answer here is regretfully ‘not really’. Soya does provide a reasonable quantity of carbohydrate (typically around 35% of the soya bean), however if we were to rely solely on soya to obtain our daily requirements of carbohydrate, we would finish up overloading on protein and fat – this might be all right for body builders and other people requiring a specialised high protein & high fat diet but is definitely not recommended for most people! The beauty of soya however lies in its ability to provide the protein and fat that we need in such a way that it can be blended with cereals to give an excellent combination of carbohydrate, protein and fat that gives us the energy we need. The World Health Organisation recommends that carbohydrate, fat and protein should provide 55-75%, 20-35% and 10-15% respectively of our total energy intake. As fat contributes far more energy to our diet than carbohydrate or protein, this suggests that optimum intakes by actual weight of macronutrient consumed should be around 70% carbohydrate and 15% each of fat and protein. A suitable blend of a high carbohydrate cereal and soya will deliver this sort of macronutrient cocktail and is particularly valuable in low-income communities where purchasing power is limited and more expensive sources of fat and protein are just not affordable. It should also be noted that the same more expensive sources of protein such as meat often contain large amounts of saturated fat whereas soya is comparatively low in saturated fat and high in the more desirable polyunsaturated fats.
What about soya as a source of micronutrients? The reality is that soya is quite a good source of certain micronutrients such as calcium and zinc but does not provide enough of the whole range of micronutrients for it to be regarded as a fully satisfactory source of all essential vitamins and minerals – it needs to be combined with other foods in order to provide these.
So it can be seen in summary that soya has enormous value as a source of protein and fat in particular and, as these are inevitably the most expensive components of food, it has major nutritional benefits in the diet when combined with other foods that are sources of carbohydrate and the various essential micronutrients. It should also be noted that soya can fairly easily be processed into forms where it is not only far more palatable than the original soya beans themselves but also where its nutritional characteristics are further enhanced and concentrated. This, along with more detailed discussions of the individual nutritional components of soya, will be covered in a series of further articles.