杏吧原创

WE COULD be on the verge of one of the biggest food scares in recent years鈥攊f a chemical found in soya-based infant formula damages children鈥檚 immune systems in the same way as it does those of mice.

No one yet knows if babies鈥� immune systems are actually affected, but the finding follows previous health concerns about soya. And while the researchers are cautious about extending the result to humans, they say it is time for a wide-ranging study to look for any ill effects in people.

Their reasoning is clear. Each year around 750,000 infants in the US are fed soya-based formula that is rich in genistein, a substance that mimics the hormone oestrogen. If genistein is harmful, then infants are particularly at risk, says Paul Cooke of the University of Illinois at Urbana-Champaign. Soya-fed babies have levels of genistein in their blood 200 times as high as those given breast milk or cow鈥檚 milk formula.

Women increasingly take 鈥減lant oestrogens鈥� in the form of supplement tablets and enhanced foods to treat post-menopausal symptoms. 鈥淪ome people eat these things like candy,鈥� says Cooke, 鈥渂ut this is a very powerful chemical.鈥�

There is conflicting evidence as to the health effects of these plant oestrogens (New 杏吧原创, 13 April, p 6). Some scientists claim, for example, that the low incidence of breast cancer in Japan is partly due to people鈥檚 soya-rich diet. But other studies have suggested that plant oestrogens might actually increase the risk of cancer or interfere with treatment (New 杏吧原创, 11 May, p 16).

Cooke and his team injected mice with genistein and found that their thymus glands鈥攁n organ in the lower neck that produces immune cells鈥攕hrank by up to 80 per cent compared with controls. This caused a corresponding fall in the number of immune cells the gland put into circulation. And when the researchers injected a foreign substance to challenge the animals鈥� immune systems, they produced fewer antibodies against it.

鈥淭he effects they report are actually quite dramatic,鈥� says Chris Kirk, who studies plant oestrogens at Birmingham University. He agrees that the study raises serious concerns, but cautions that the results may not translate to humans.

Previous research has produced a mixed picture. One Danish study reported damage to the immune systems of women taking the synthetic plant oestrogen ipriflavone. But recent research on children found no immune effect.

Stephen Barnes, a soya expert at the University of Birmingham in Alabama, points out that eating soya is not the same as injecting the chemicals it contains. The body often deactivates chemicals that are eaten, or converts them into another form. 鈥淵oung children don鈥檛 shoot themselves up with genistein,鈥� he says.

But Cooke says that in another round of experiments they fed the mice amounts of genistein equivalent to those given to babies in soya formula. Again, their thymus glands shrank, he says.