Friday, December 02, 2005

GM peas

It may surprise some of you who believe my opinions are utterly predictable, but I don't have a hard and fast view about Genetically Modified Organisms (GMOs). I have heard a number of worrisome things and it isn't hard to conjure up unsettling scenarios involving monoculture, monopoly and adverse health effects, but there is not much to go on in the way of empirical evidence, which makes having an opinion more difficult (or maybe it makes it easier?).

Anyway, this is not an area I study intensively, but I do keep my eyes open for bits and pieces of evidence one way or another. So I read with interest a piece in New Scientist about the abandonment of a decade long research project in Australia to insert a gene into Field peas (Pisum sativum) for alpha amylase inhibitor-1, a protein that kills pea weevil (Bruchus pisorum) by inhibiting alpha amylase which the weevil needs to digest starch. Purified alpha amylase inhibitor-1 doesn't cause allergic reactions in humans or mice. So there was every reason to believe it was a safe modification, at least as far as human health was concerned.

Surprise. Mice that ate the peas developed allergic reactions when later exposed to the purified protein. When injected with the protein mice developed a hypersensitive skin response and when exposed through inhalation, airway inflammation and mild lung damage.
The effect was the same whether the protein was taken from raw or cooked peas – so whether the protein was active or denatured. “To my knowledge, this is the first description of inducing experimental inflammation in mice” with a GM food, [Paul Foster of the Australian National University in Canberra] says. In the early 1990s, researchers engineered a more nutritious strain of soya bean by adding a gene taken from brazil nuts. But the project ended when it was discovered that the hybrid was likely to trigger a major attack in people with brazil nut allergies.


Further investigations by Foster’s team revealed slight differences in the molecular structure of the protein when it was expressed in the bean and in the pea. They think this was caused by differences in the way the two plants produce proteins – particularly in a step called glycosylation, which involves adding saccharides to the protein.

“When expressed in the pea, the protein was glycosylated at different points – that’s the only structural change we’ve been able to identify so far,” says Foster. (New Scientist)
Foster emphasizes the importance of looking at GM crops on a case-by-case basis with adequate and sophisticated tests.
He adds that slight differences in protein synthesis might also occur in other plants with other genes, meaning each new GM food should be very carefully evaluated for potential health effects. “If a GM plant is to go up for human consumption, there should be a detailed descriptive list of how one should go about analysing that plant,” he says.

“These results indicate the potential for unpredicted and unintended changes in the structure of transferred proteins. And I’m not aware of any country that requires feeding studies as part of its approval process.”
Jeremy Tager, Greenpeace Australia’s campaigner on genetic engineering, drew another lesson:
It is rare for an investigation of the potential health effects of a GM product to be published in a peer-reviewed journal [Journal of Agricultural and Food Chemistry (vol 53, p 9023)], he adds. “If it had been a private company doing this, it might never have seen the light of day,” he says.
Ya think?