soya
by Jenny Bryan
Soya is a protein-rich food, made from soya beans, which is low in saturated fat and cholesterol. Soya beans can be soaked, crushed and heated to produce soya milk. This may then be mixed with a thickening agent to produce soya curd and pressed to give tofu, also called soya cheese. Silken tofu is soft and creamy while firmer, denser forms are usually smoked or marinated.
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Soya flour, made by extracting the oil from soya beans, can be processed and dried to produce spongy textured vegetable protein (TVP) which is often flavoured and cut into chunks to look like meat.
Other soya products include tempeh – fermented soya bean paste – which is also used as a meat substitute, and miso – a fermented mix of soya beans, rice or barley, salt and water – which is used to flavour sauces, soups and casseroles. Soya sauce (shoyu) is made by fermenting soya beans with cracked roasted wheat, salt and water, while tamari sauce is similar but stronger and made without wheat.
why is soya good for you?
Western health researchers became interested in soya when they realised that people living in Japan and south east Asia, where soya is a dietary staple, are less likely to have heart disease or prostate, breast, womb and ovarian cancers. Women living in these countries also seem to experience fewer unwanted symptoms when they reach the menopause.
Some countries are more impressed with the evidence than others. In the USA, food manufacturers can claim that soya protects against heart disease when included in a low fat diet, but such products must include at least 6.25g of soya protein in each serving. In contrast, British experts are still assessing the evidence (see can functional foods claim to be healthier?)
what's the evidence?
Soya beans, like many vegetables and pulses, contain phytoestrogens (plant oestrogens). The main types of phytoestrogen are flavonoids found mainly in lentils, chick peas, soya beans and groundnuts, and lignans, found in vegetables, fruits, grains and beans.
There are several types of flavonoid and, of these, the isoflavones have been most carefully studied for their effects on health.
Research has shown that soya consumed in the diet or as isoflavone-containing supplements can reduce cholesterol levels, though not by the amounts achieved with cholesterol lowering drugs, such as statins. Reductions are closer to those achieved with cholesterol lowering spreads, such as Flora pro-activ and Benecol.
Laboratory studies have also shown isoflavones, such as genistein, make blood vessels relax and get wider, and so they may reduce the risk of blocked arteries, heart attacks and strokes.
what about cancer?
There is no direct evidence that eating more soya in your diet will reduce your risk of cancer. The fact that certain forms of cancer are less common in Japan and south east Asia does not necessarily mean that soya is the link, or that changing our diet would have the same effect. There are many genetic, dietary and lifestyle differences between people who live in Europe and the USA and those who live in the Far East, and any or all of these may play a role in what diseases we get.
soya and menopausal symptoms
Recent studies have failed to show any effect of isoflavone-rich foods or supplements on menopausal symptoms compared to placebo, or dummy, supplements. However, some women do seem to get relief from menopausal symptoms when they take supplements, such as red clover, which are rich in phytoestrogens.
As a source of oestrogen, albeit plant oestrogen, it has been suggested that a soya-rich diet could also help prevent post-menopausal health problems, such as osteoporosis (brittle bones). Interestingly, a recent study on pre-menopausal Chinese women in Hong Kong showed that those with the highest soya consumption also had the strongest bones. But, once again, there's no real evidence that such findings translate to British women.
help and info
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organisations
Breast Cancer Care
Kiln House
210 New Kings Road
London SW6 4NZ
Helpline: 0808 800 6000 (Mon-Fri 10am-5pm, Sat 10am-2pm)
Website: www.breastcancercare.org.uk
Offers information and support to women and men who have or fear they may have breast cancer, to their friends and family, and to anyone who wants information about any aspect of breast health. Provides free booklets and leaflets, many of which are available on the website.
The Prostate Cancer Charity
3 Angel Walk
London W6 9HX
Helpline: 0845 300 8383 (Mon-Fri 10am-4pm)
Website: www.prostate-cancer.org.uk
E-mail: info@prostate-cancer.org.uk
Staffed by experienced prostate cancer nurses, the helpline offers comprehensive information on prostate cancer, including symptoms, diagnosis and treatment, plus a list of nationwide support contacts and free literature.
websites
Vegetarian Society
www.vegsoc.org/info/soya.html
Information sheet looking at soya and its health benefits. Describes different types of soya foods and features resources for further information.
British Nutrition Foundation (BNF)
www.nutrition.org.uk
Features information about the BNF, plus nutritional advice and information.
Institute of Food Research
www.ifrn.bbsrc.ac.uk/public/FoodInfoSheets/soya.html
Factsheet on soya, its history, cultivation and nutritional benefits.
Health and Nutrition
www.healthandnutrition.co.uk/articles/premenst.htm
A website on natural health including an article by Suzannah Olivier called Menstrual Mayhem, suggesting soya as a useful ingredient in combating problem periods and restoring hormone balance.
Scottish Association of Prostate Cancer Support Groups
www.prostatescot.co.uk
Gives excellent advice about what questions to ask once diagnosed, plus a database of local Scottish support groups.
Soja-Net
www.soya.co.uk
A wealth on information on soya, including health benefits and recipes.
Soyfoods
www.soyfoods.org
US site which features factsheets on different types of soyfoods, nutritional information, news and recipes.
reading
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The Soy Zone by Barry Sears (HarperCollins, 2001) |
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Super Soya: Recipes and Facts for Greater Health by Tanya Carr and Joanna Farrow (Hamlyn, 2005) |
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(October 2001, resources updated March 2005)
