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The Soya StorySoya: the superbean! The nutritional power of soya
‘Soya bean’ in Chinese means ‘greater bean’. A look at its nutritional content shows that this is a most fitting title. However, this food is not without its detractors and I address their concerns below.
Products and supplements using extracts of soya have had many of the beans’ nutrients removed and do not contain the wealth of health benefits of whole soya foods. However, this doesn’t mean they shouldn’t be included in a balanced diet. For example, from a health (and ethical) perspective mock meats are superior to their meat counterparts. Textured vegetable protein (TVP) is basically defatted soya flour which has been processed and dried to give a substance with a spongelike texture which may be flavoured to resemble meat. It is a good source of fibre and protein, and is often fortified with vitamin B12. Protein packed The soya bean is a legume – a type of plant in which the seeds grow in pods. All edible beans are nutrient powerhouses – they have to be to support the rapid growth of a new plant – but soya is particularly impressive. Soya beans are an excellent source of protein (approximately 40 per cent) as they contain all eight essential amino acids – building blocks of protein – which we need in our diet because we cannot manufacture them. But the gold standard for measuring protein quality is the snappily worded Protein Digestibility Corrected Amino Acid Score. This takes into account not just the amino acid composition but also the digestibility of the protein. Soya gets almost top marks for both – in other words, it is a wonderful source of highquality, health-promoting protein which we digest easily and efficiently (FAO/WHO, 1989). Protein is vital for growth, development and repair of body tissues and is needed to make the thousands of enzymes required for the bewildering myriad of chemical reactions that take place inside us. Every neurotransmitter is made from protein and they enable our nerves to send messages from cell to cell. The brain cannot function without protein and a diet deficient in it can lead to depression, apathy, poor memory, insomnia, lack of motivation and an inability to concentrate.
Don’t tryp up!
A weighty topic
And trypsin inhibitors? 
In fact, oriental foods such as tofu, miso, soya sauce and other soya bean foods such as soya infant formula are, according to the US Department of Agriculture (USDA), “generally low in trypsin inhibitor” (Anderson et al., 1995). The USDA also states that trypsin inhibitors in soya beans are thought to help prevent cancer. So, not such a bad thing after all!
Sapping saponins Phytoestrogens are natural plant hormones found in many fruits, vegetables, dried beans, peas and wholegrains. Phytoestrogens in soya (called isoflavones) are responsible for many of the health benefits of soya (see pages 10-11).
Phytic acid If you still want to lower your phytic acid intake, fermented soya products such as tempeh have much lower quantities – about half that of soya beans (Anderson et al., 1995).
Fab fats The fatty acids in soya are important hormone precursors, vital for making healthy new cells, stabilising blood pressure and promoting smooth muscle contraction. Soya – as with all plants – is completely cholesterol-free. Compared to cow’s milk, soya milk contains lower levels of saturated fat and higher levels of valuable unsaturated fats, which can help lower cholesterol levels. In 2006, the American Heart Association highlighted the valuable role that soya foods can play in replacing higher-saturated-fat foods in the diet and so helping to lower blood cholesterol levels (Sacks et al., 2006).
Fibre rich We should eat a minimum of 18g of fibre a day yet most people in the UK eat only about 12g. A 4oz/100g serving of soya beans contains 9.3g of dietary fibre. Tofu and soya milk have little fibre, whereas edamame, tempeh and soya flour are very good sources.
Lovely lecithin Lecithin and choline have many health benefits, for example helping prevent heart disease, improving brain function and memory and supporting the liver. Choline is used by the body to help remove cholesterol and aids the digestion of fats. One of the richest sources of lecithin is soya.
Vitamins and minerals
Dem bones Without fortification, 4oz/100g of green, cooked soya beans (edamame) contain 145mg of calcium; 21 per cent of an adult’s daily needs. The same weight of calcium-set fried tofu contains 961mg (137 per cent of our daily needs)! An extremely good source either way. It is sometimes claimed that the bioavailability of calcium from soya milk is not as high as from dairy milk. Scientists compared the bioavailability of cow’s milk with that of calcium-enriched soya milk and revealed that they are comparable. It follows that soya is a good source of calcium! (Zhao et al., 2005.)
Mighty magnesium About two-thirds of all the magnesium in our body is in our bones and, like calcium and phosphorus, is vital to bone health. Magnesium and calcium act together to help regulate the body’s nerve and muscle tone. Simply put, magnesium relaxes muscles while calcium contracts them. Magnesium deficiency can trigger muscle tension and soreness, muscle spasms or cramps and muscle fatigue. Over 300 different body enzymes need magnesium and so it follows that the functions of this mineral are particularly diverse. Magnesium is central to energy production as well as being involved in the metabolism of proteins, carbohydrates and fats. It also helps genes function correctly. Soya is also a rich source of magnesium, with 4oz/100g containing 280mg – practically all of our daily needs. The same weight of edamame and cooked tempeh provides 22 per cent while raw tofu provides about 10 per cent.
Finally…
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The Soya Story - ContentsResources:
Myth-Busting Soya and the Environment FAQs Soya research |
Soya is best eaten cooked in its whole form as green soya beans (edamame), tofu or fermented as tempeh or miso (see pages 31- 32). This ensures that the variety of nutrients and their quality remains high. Soya milks are also a healthy product but choose those brands that use the whole soya bean rather than those which use soya protein extract – it says on the ingredients list.
Soya beans are one-fifth fat and of this, 78 per cent are the ‘good’ fats, called polyunsaturated fatty acids. In fact, the soya bean is one of the few good plant sources of the essential fatty acid, alpha-linolenic acid (ALA), an omega-3 fatty acid that the human body can’t make.
The Soya Story
The Safety of Soya 
Soya-Based Infant Formula 
The Soya Saga  |
Vegetarian & Vegan Foundation Top Suite, 8 York Court, Wilder Street, Bristol, BS2 8QH, UK T: 0117 970 5190 W: www.vegetarian.org.uk E: info@vegetarian.org.uk |
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