New research today raises fresh fears over the safety of genetically modified food after it was shown that a GM product could affect human blood cells.
A Scottish team reports that a natural insecticide found in the snowdrop and used in GM experiments binds strongly to human white blood cell proteins.
The health implications of this are unknown. But white blood cells are essential components of the immune system and any effect on their functioning could have serious consequences.
Scientists led by Dr Brian Fenton, from the Scottish Crop Research Institute in Dundee, outline the findings today in the British medical journal, the Lancet.
They say the study highlights the need for "much greater understanding" before such products could safely be released into the food chain.
The British government welcomed the new research. A spokesman for the Cabinet Office said: "It acknowledges that further studies need to be carried out in this area. We wait with interest to see the reactions from the wider scientific community."
Mr Charles Secrett, executive director of Friends of the Earth, one of the pressure groups involved in anti-GM campaigns, called on the British government to suspend all GM food approvals and "instigate an assessment of the best methods to research their safety".
Dr Fenton's team investigated the effects of the snowdrop lectin protein, GNA, which naturally protects the plant from insects and worms. Scientists are looking into ways of introducing the lectin gene into food crops, such as potatoes and soya, to give them the same protection. Eating such crops would mean consuming both the altered gene and the GNA lectin it produces.
The Dundee researchers examined the effect of GNA on blood cells taken from six healthy volunteers. They found that red blood cells showed little reactivity, but there was a powerful effect on white blood cells.
The scientists wrote: "Our results show that human white blood cells have many proteins that strongly bind to GNA . . . This work highlights the need for a much greater understanding of the interactions between plant lectins and human glycoproteins (sugar proteins) before they can be safely incorporated into the food chain."
The Lancet published the controversial results of Dr Arpad Pusztai's work with rats, which involved the same snowdrop protein and helped to trigger the whole GM debate.
Dr Richard Horton, editor of the Lancet, has been criticised for publishing the research of Dr Pusztai and Prof Stanley Ewen which concluded that rats fed GM potatoes containing the snowdrop insecticide gene suffered stomach and intestine disorders. Dr Pusztai was forced to retire from his job at the Rowett Research Institute in Aberdeen last year after discussing his experiments on a television programme.