Why soya may not be such a super food after all

(Agencies)
Updated: 2009-04-27 16:19

The soya plant boasts high levels of phytoestrogens that mimic the action of the body's own oestrogen. And 100g of tofu contains 12.9mg of phytoestrogens, while 100g of soya yogurt or soya milk contains 11.8mg.

Dr Margaret Ritchie, an expert in phytoestrogens at the University of St Andrews, explains: 'These oestrogen-like chemicals are up to 20,000 times weaker than natural oestrogen. If a woman is low in oestrogen, as in the menopause, the extra oestrogen absorbed when soya is eaten can help relieve menopausal symptoms.'

It may also reduce the impact of the body's own oestrogen on breast and womb tissue, protecting against breast and uterine cancers, which are triggered by the hormone.

However, according to recent studies published in the Journal Of Nutrition, soya baby formula could cause problems in male infants.

Research at Edinburgh University into the effects of soya milk on young male monkeys found it interfered with testosterone levels, prompting concerns over fertility and disease in grown men.

Furthermore, studies in Japan suggest a high intake of soy-based products can disrupt the thyroid gland, leading to weight gain, fatigue and mood problems.

Marilyn Glenville, nutritionist and author of the Nutritional Health Handbook For Women, says: 'Soya can block the uptake of the chemical iodine which is needed for a healthy thyroid. Turnips, cabbage, peanuts and pine nuts have similar effects. If you are diagnosed with a thyroid problem, you'll be told to restrict your intake of all these foods.'

She adds: 'The soya in soy burgers and sausages and added as flavour enhancers is highly processed. The soya-bean fibre is removed and the residue is soaked in an aluminium tank, then treated with chemicals such as nitrates, which some studies have linked to cancer.'

Glenville recommends reducing overall intake of processed foods and increasing intake of wholefoods.

The British Nutrition Foundation recommends adding traditional soya-bean products such as tofu, tamari, miso and tempeh to a healthy and varied diet.

'Don't overdo it,' warns Glenville. 'It is healthy in small quantities, but could be unhealthy if eaten in excess.' One small portion, about 30g, a day is ideal.

And as there is evidence linking GM soya to a raised allergy risk, ensure any soya products you buy are organic and therefore GM free.

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