Scientists versus the soya industry.

Twelve years ago, I visited an alternative health practitioner with some non-specific health symptoms. I'd hardly sat down before he told me that my diet needed radical attention - I had to cut out all dairy, wheat, alcohol and caffeine, and substitute protein in the form of soya milk and tofu instead. Nowadays this kind of advice is routine, but at the time, it seemed glamorously radical: I had to trek to Clapham's one health-food shop to stock up on soya milk because Sainsbury's certainly didn't have their own brand (as they do now) and veggie/soya sausages were just a glint in Linda McCartney's eye.

In the event, I lost a stack of weight and felt immensely rejuvenated. So much so that, four months later, I started eating normally again. Just as well, because it has now been found that soya - far from having the magical, health-giving properties that the alternative medicine brigade endlessly bangs on about - can actually be bad for you. Its reputation as an anti-cancer, cholesterol-lowering, osteoporosis-fighting, low-fat all round good egg of a product is based on bad science and superlative marketing by the powerful soya industry.

Worldwide, the evidence is starting to stack up against soya. In this country, MAFF is so worried about the possible health problems of phytoestrogens in soya that they are funding a rolling programme of 19 separate research projects, due to end in 2002. Preliminary findings by Professor John Ashby of AstraZeneca Central Toxicology Laboratory in Macclesfield, for example, confirm that soya infant formula (currently the sole food of 6,500 British babies) has an oestrogenic effect on rats. According to public health minister Yvette Cooper, no new advice will be given on soya until the independent COT (Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment) has reviewed the programme's findings.

This could take several years. Meanwhile, if you've been seduced by the message that soya is the healthy 21st-century superfood, read on...

Is soya bad for you?

It contains high quantities of various toxic chemicals, which cannot be fully destroyed even by the long cooking process. These are: phytates, which block the body's uptake of minerals; enzyme inhibitors, which hinder protein digestion; and haemaggluttin, which causes red blood cells to clump together and inhibits oxygen take-up and growth. Most controversially of all, soya contains high levels of the phytoestrogens (also known as isoflavones) genistein and daidzein, which mimic and sometimes block the hormone oestrogen.

Surely, the Japanese eat huge quantities of soya, and as a result have low rates of breast, uterus, colon and prostate cancers?

That's the big myth on which the idea of 'healthy' soya is built. In fact, the Japanese don't eat that much soya: a 1998 study showed that a Japanese man typically eats about 8g (2 tsp) a day, nothing like the 220g (8oz) that a Westerner could put away by eating a big chunk of tofu and two glasses of soya milk. Secondly, although Japanese people may have lower rates of reproductive cancers, this is thought to be due to other dietary and lifestyle factors: they eat less fatty meat, more fish and vegetables and fewer tinned or processed foods than in a typical Western diet. Thirdly, Asians have much higher rates of thyroid and digestive cancers, including cancer of the stomach, pancreas, liver and oesophagus.

I'm vegetarian and eat loads of tofu and soya milk. Should I stop?

Soya has become vegetarians' meat and milk, the major source of protein in their diet. But eating soya actually puts vegetarians at severe risk of mineral deficiencies, including calcium, copper, iron, magnesium and especially zinc. According to Dr Mike Fitzpatrick, a New Zealand biochemist who runs a soya information website (see below), this is because soya contains high levels of phytic acid, which blocks the absorption of essential minerals in the digestive tract. To reduce the effects of a high-phytate diet, you need to eat, as the Japanese do, lots of meat or fish with tiny bits of soya.

I'm intolerant to cow's milk, so should I drink soya milk instead?

Soya has become the fashionable option for people 'intolerant' to dairy products. It's little known that soya is the second most common allergen. Only 1 per cent of the population is truly allergic to cows' milk and, of those, two-thirds will also be intolerant to soya milk. In addition, soya milk is high in aluminium. That's because the soya protein isolate it's made from is acid-washed in aluminium tanks. No wonder it tastes bad.

Can soya affect your thyroid?

It's been known for years that phytoestrogens in soya depress thyroid function. In Japan, 1991 research showed that 30g of soya a day results in a huge increase in thyroid-stimulating hormone. This can cause goitre, hypothyroidism, and auto-immune thyroid disease.

I'm pregnant. Should I avoid soya?

Probably, and especially if you're vegetarian. A new study of babies born to vegetarian mothers showed that baby boys had a five-fold risk of hypospadias, a birth defect of the penis. The researchers suggest this was due to greater exposure to phytoestrogen rich-foods, especially soya. Inappropriate hormone levels such as that caused by a high intake of soya during the first 12 weeks of pregnancy can also cause damage to the foetus's developing brain.

But surely I can feed my baby soya formula? It must be safe: it's available in every supermarket and chemist.

Soya-fed babies are taking part in 'a large, uncontrolled and basically unmonitored human infant experiment', said Daniel Sheehan, director of the FDA's National Center for Toxicological Research, in 1998. A newborn baby's sole food is the milk it drinks: a soya-fed baby receives the equivalent of five birth control pills' worth of oestrogen every day, according to Mike Fitzpatrick. These babies' isoflavone levels were found to be from 13,000 to 22,000 times higher than in non-soya fed infants.

As a result of this phytoestrogen overload, soya-fed babies have a two-fold risk of developing thyroid abnormalities including goitre and auto-immune thyroiditis. Boys risk retarded physical maturation, while girls risk early puberty (1 per cent of girls now show signs of puberty, such as breast development or pubic hair, before the age of three) and fertility. Researchers have also suggested that diabetes, changes in the central nervous system, extreme emotional behaviour, asthma, immune system problems, pituitary insufficiency and IBS may be caused by high phytoestrogen intake in early life. Last year, compounds in soya were also implicated in the development of infantile leukaemia. Current government advice is that breast is best and that soya formula should not be given to infants unless on the advice of a health professional.

Can soya help with prostate cancer?

Ex-junk bond trader Michael Milken certainly thinks so. He consumes 40g of soya protein every day with that hope in mind. The science is less conclusive - a recent study on Japanese-Americans living in Hawaii showed that men who had eaten two or more servings of tofu a week during mid-life not only had 'accelerated brain ageing', and more than twice the incidence of Alzheimer's and dementia, but also looked five years older than those men who didn't.

My mother died of breast cancer and I've been advised by both mainstream and complementary medical sources that increasing my soya intake may offer me protection against the disease. Is this true?

The evidence is highly inconclusive. In The Breast Cancer Protection Diet , published last year, Dr Bob Arnot states that eating between 35g and 60g of soya protein daily protects against breast cancer by raising intake of the oestrogen-blocker genistein. But this ignores contrary evidence. In 1996, research showed that women eating soya had an increased incidence of epithelial hyperplasia, a condition that presages malignancy. In 1997, genistein in the diet was also found to stimulate human breast cells to enter the cell cycle. As a result, the researchers advised women not to eat soya products to prevent breast cancer.

But surely soya prevents osteoporosis, the bone thinning that particularly affects post-menopausal women?

No. In fact, soya blocks calcium and causes a deficiency of vitamin D, both of which are needed for strong bones, say American nutritionists and soya debunkers Sally Fallon and Mary G Enig.

Is there any kind of soya product I can safely eat?

Yes. Fermented soya products, such as soy sauce, tempeh and miso. The long fermentation process counteracts the effects of natural toxins in soya.

Can I avoid soya?

It's hard. You can stop eating the obvious candidates such as soya milk and tofu, but soya is also to be found in breakfast cereals, ice cream, convenience food such as hamburgers, fish fingers and lasagne, and all manner of baked goods from cakes and biscuits to tortillas and bread. If that's your mission in life, read labels carefully, and eat organic processed foods wherever possible.

Finally, the pro-soya lobby always says that, in the US, a quarter of the population has been fed infant soya formula for 30 to 40 years, with no adverse health problems. So why should I worry?

Scientists are only just beginning to research and understand the harmful long-term effects that eating large quantities of soya can have on the human body. As Fallon and Enig write: 'The industry has know for years that soya contains many toxins. At first they told the public that the toxins were removed by processing. Then they claimed that these substances were beneficial.' Sounds like there's a big battle ahead.

• For further information, contact www.soyonlineservice.co.nz, a detailed information resource on soya run by biochemist Dr Mike Fitzpatrick. Sally Fallon and Mary G Enig's excellent article 'Tragedy and Hype: The Third Soy Symposium' is on www.nexusmagazine.com. 'The Trouble With Tofu: Soya and the Brain' by John D MacArthur is on www.brain.com

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