Soy - Wonder Food Or
Health Hazard?
By Suzannah Olivier
The Times - London
Soy has been hailed as a wonder food for several conditions, including heart disease, breast cancer, prostate cancer, menopausal symptoms and bone health.
Yet recent media reports suggest that it may be harmful, a view spearheaded by an article in Nexus magazine. The piece was critical of soy products, though the data on which it was based referred mainly to whole soy beans rather than soy products such as tofu and soy milk. Most soy-based products are processed, which destroys or minimises the "anti-nutrients discussed in the article.
The report denounced soy protein isolates (SPIs), which are processed differently from tofu and are used by the food industry as "hidden bulking agents for many foods, including baby formulas. SPIs have been criticised for high aluminium levels because of the way that they are processed. Good-quality brands of soy products such as milks, desserts and yoghurt have low levels of aluminium; in soy milk it is less than that found in water and in cow,s milk.
It is worth understanding why soy is supposed to be so beneficial. The British Nutrition Foundation (BNF) says that compounds in soy, isoflavones, have been shown to have oestrogenic and anti-oestrogenic effects. They vie with a human oestrogen, oestradiol, to bind with the oestrogen receptors in cells, but on binding they fail to stimulate a full oestrogenic response, and evidence is building that this may offer protection against a range of hormone-related conditions, including breast, bowel, prostate and other cancers and, possibly, menopausal symptoms.
Isoflavones also have strong antioxidant properties, and soy is a source of soluble fibre that can lower cholesterol levels.
Some experts believe that "foreign oestrogens to which we are exposed in our environment " the xenoestrogens that come from plastics, pesticides and dioxins " can be crowded out by soy isoflavones, rendering them less capable of creating the hormone havoc of which they are suspected.
In her book Our Stolen Future, Theo Colborn accuses these environmental oestrogens of being involved in breast and other cancers, as well as lowered sperm counts in men and malformed genitals in baby boys.
After menopause, when fewer oestrogens are available " increasing the risk of osteoporosis and heart disease " isoflavones are thought to act as weak hormone replacement therapy because of their mildly oestrogenic effect, which seems to improve the prognosis for these conditions.
The US Food & Drug Administration has approved a health claim on foods that contain 6.25g of soy protein per serving. US manufacturers are allowed to state that eating 25g of soy protein a day, as part of a diet low in fat and cholesterol, may reduce the risk of heart disease.
The FDA declined to say that isoflavones were responsible for aiding heart health, but instead agreed that the whole soy protein conferred protection.
So what about the criticisms? While isoflavones have excited the most research, it is probable that other compounds in the soy bean are partially responsible for the overall effect.
Probably the main criticism is of claims by supplement manufacturers extolling the virtues of isolated soy isoflavones for conditions such as breast cancer, heart disease and menopausal symptoms. Shelves in health-food shops are laden with such supplements.
In fact, there is concern that these supplements could actually increase the risk of breast cancer if taken to excess, and some supplement manufacturers have marketed high-dose isoflavone supplements for breast enhancement, which is patently a bad idea. To be on the safe side, and in the absence of solid research evidence, it is safest to advise those with breast cancer not to take supplements that contain isolated isoflavones.
Professor Keith Griffiths is researching the effects of isoflavones on prostate cancer at the Tenovus Cancer Research Centre at the University of Wales College of Medicine. "Isoflavones stand out as compounds that stop prostate cancers developing into their aggressive form, he says. "But we use complete soy protein in the research because, while we believe isoflavones are the interesting compounds, we might be missing something if we use them in isolation. Similar factors are involved in breast and prostate cancer.
The point has been made that while Japanese and other Eastern cultures enjoy substantially lower incidences of breast cancer, their diet is so different from that in the West that many other factors must be considered. In my book about diet and breast cancer, eating soy is the fifth of 12 points covered. I recommend eating fruit and vegetables, oily fish and pulses and changing the fats in the diet, and only then eating around 100g (4oz) of tofu (or similar) five times a week (equivalent to 70g daily). A bit of what you fancy may do you good, a lot may do the opposite.
Stephen Terrass, the director of Solgar Vitamins and a nutrition expert, says: "If future research were to corroborate recent safety concerns, it would likely be relative to the quantity of soy consumed rather than inherent problems with isoflavone-rich foods. No food can be consumed in unlimited quantities.
There have also been suggestions that soy is linked to suppressed thyroid function, increased risk of Alzheimer,s disease, mineral deficiencies and possible effects on fetuses. Pointing out that much of the research cited to support these claims has been based on work with animals rather than human beings, the BNF regards them as "speculative and unproven.
The authors of a paper on tofu consumption and brain aging published in the Journal of the American College of Nutrition note in their conclusions that the men who ate the most tofu were more likely to have spent their childhood in Japan and in greater poverty, and that a nutritionally deprived childhood was more likely to be responsible for ageing of the brain than tofu intake.
Some people are sensitive, or allergic, to soy and there is no rule that we must obtain isoflavones from just this source. Other foods rich in these compounds include chickpeas, beans, pulses, grains, nuts, vegetables and fruits, and isoflavone levels are also higher in the Mediterranean diet, which features these foods.
But if soy agrees with you, eating a moderate amount as part of a mixed diet is likely to do more good than harm. I had breast cancer 12 years ago and still eat it.

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