Curious Cook: The verdict’s still out on genetically modified food

A forbidden sign made by Greenpeace is seen in a field which the environmental group claims contains genetically modified corn in the northern Spanish town of Zuera in 2006. Photo: Reuters

Quite a few people have asked for an opinion about the safety of genetically modified (GM) foods – and the correct (and totally verifiable) response has always been, “I don’t know”. You can perhaps ask a better question, which is, “What are the long-term benefits of GM foods?” And the answer is also “I don’t know”.

It is rather annoying but after reading a lot of research papers on GM crops, the answers are still definitely not available.

It has to be added that much of the research into the safety of GM foods are funded by the chemical industry – and the limited research which expressed misgivings about GM products often had their conclusions rebutted vigorously, presumably by the pro-GM lobby.

Regardless of who is right or wrong, the European Union has imposed strict controls on the proliferation of GM crops, which is not the case in other regions of the world, especially the United States.

The situation regarding GM food might be considered as a big fork in the river of human existence: either the world has embarked on an ambitious but dangerous scientific experiment, led by a few chemical companies – or we are really on the road to eliminate human famine for the foreseeable future.

As GM foods cover a huge range of products, let’s just explore a few aspects about food crops which have made the news recently.

How GM crops work

Food crops can have their genetic makeup altered in several ways, but primarily, the objective is to increase the yield of the crop either by making it grow better and faster (preferably using less fertiliser, water or other resources), improving its resistance to loss due to pests, or both.

As regards improving yields, this is generally achieved by the rather uncontroversial technique of mixing and breeding hybrids of various strains of a crop to maximise the yield achievable by the plant species – and in fact this has been going on for thousands of years.

GM crops get rather interesting when genetic material from another unrelated species is introduced into the genetic structure of plants. As an example, a gene from the bacterium, Bacillus thuringiensis, had been introduced into GM corn since the early 1990s. The reason is rather ingenious – for this bacteria produces a natural pesticide called Bt-toxin which causes the stomachs of insect pests to break down into mush or sometimes even explode.

Genetically modified corn threatens corn biodiversity. Photo: USDA
Genetically modified corn threatens corn biodiversity. Photo: USDA

The aggressive toxicity of Bt-toxin is not really a surprise because bacillus thuringiensis comes from the same family as bacillus anthracis, which causes a very deadly human disease known as anthrax.

Before GM corn got into the picture, Bt-toxin had been the world’s largest-used biological pesticide for some time.

With GM corn, the strategy was to insert a gene from Bacillus thuringiensis that would cause the corn to produce its own Bt-toxin – this was done with the express intention of making the corn itself kill any bugs that may want to eat it.

Needless to say, there were quite a few people who disapproved of the idea – many were simply against the idea of eating toxin-producing corn, and a group of scientists also protested that this strategy would only create variants of bugs which would become immune to Bt-toxin.

However, Monsanto (who had the patent) won the arguments and introduced two strains of Bt corn called MON810 and MON863 – and most of the US corn harvest is now based on Bt corn.

If you’re curious, the pesticide expressed by MON810 is called modified Cry1Ab toxin and MON863 expresses modified Cry3Bb1 toxin – weight for weight, Bt corn produces thousands of times more toxins than the original Bacillus thuringiensis.

For the people who didn’t like the idea of eating toxin-producing corn, Monsanto assured them that Bt corn was perfectly safe and coincidentally a whole slew of research papers supported Monsanto.

So based on available evidence at the time, Bt corn was deemed safe to ingest. One claim was that Bt corn simply cannot cause problems in mammalian guts but in 2008, an Italian study on mice fed with Bt corn MON810 indicated that there are tangible side effects, such as allergies and inflammation of the gut.

Other studies also appear to support the Italian research. Another claim that the gene producing Bt-toxin can be translocated to other bacteria in the human gut flora and therefore continue to produce Bt-toxin in the intestines has not been conclusively proved.

And, to be fair, studies to date still have not proved that ingesting Bt corn in normal quantities has had any confirmed harmful health effects in humans – one reason may be because most of the studies are limited to only 90 days for some odd reason.

An interesting side effect of Bt corn is that it can prove rather difficult to compost – because the Bt-toxin is also pretty effective against the normal bacteria and fungi that would normally decompose organic material.

However, the other scientists who worried that Bt corn would create strains of bugs which are immune to Bt-toxin were sadly proved right. In 2011, a serious pest called the western corn rootworm (known as Diabrotica virgifera virgifera) was found happily munching away at the roots of a Bt corn field.

The significance is not that an insect species had adapted to tolerate a toxin, the real problem is that the US had grown so dependent on Bt corn that 65% of the corn grown in the USA is effectively a monoculture (ie. only one species of corn is grown – Bt corn).

Ironically, normal non-Bt corn crops next to these infected Bt corn fields were relatively unaffected by the rootworm – hence it may be that the new strain of rootworm actually prefers Bt corn. If this new strain of rootworm spreads, the economic damage to the US corn industry would be incalculable.

The other GM strategy

So we now know that GM crops can produce their own pesticide – but the agricultural biochemists weren’t finished yet. They came up with another bright idea to create crops that was resistant to a single toxic herbicide called glyphosate (commercially known as Roundup).

The idea was simple – farmers plant GM crops which are genetically immune to glyphosate, then spray the crop fields with the herbicide – and all the unwanted weeds (and other plants) are gone, leaving only the required crop standing. Monsanto even created a brand around this approach, called Roundup Ready (RR) – Monsanto is the only producer of glyphosate or Roundup

Quite a few people, unsurprisingly, raised some objections. As a crop production strategy, this approach clearly has some flaws. For one, it makes farmers dependent on glyphosate – because that was the only herbicide that won’t kill their own crops.

Environmental advocates carry over their heads a giant purple globe, which participants say represents their unhappiness towards genetically modified organism products in Manila in this October 2014 file photo. Photo: Reuters
Environmental advocates carry over their heads a giant purple globe, which participants say represents their unhappiness towards genetically modified organism products in Manila in this October 2014 file photo. Photo: Reuters

Another problem is that every crop field instantly becomes a monoculture as the little grasses, hedges and miscellaneous plants which normally don’t affect the crop would get killed.

This means the biodiversity of such fields is destroyed as other insects, reptiles and mammals which depend on the other plants would also die off. The concentration of glyphosate in the ground will also increase as only one herbicide is applied again and again and more weeds will develop resistance to the herbicide. And so on.

That last item about weed resistance has already happened. Over 30 weeds, with varying degrees of perniciousness, have already developed at least some resistance to glyphosate, and some scientists now call them “superweeds”.

What is actually perhaps more of a concern is that a study published in the journal Food And Chemical Toxicity indicated that rats fed on RR maize had significantly higher incidence of tumours than control rodents. The cause is unclear and may be due to the genetic structure of the RR maize or perhaps an excessive residue of glyphosate in the maize.

Although Monsanto has stated that Roundup is a safe herbicide with a “low risk to human health”, there have been many studies which beg to differ. Low doses of glyphosate have been implicated in birth defects found in frogs and chickens. 
Other studies suggested that even at doses below those recommended for crop spraying, glyphosate can cause cancers, endocrine (hormone) disruption and DNA damage in mammals.

Most damning is the declaration from the International Agency for Research on Cancer (IARC) – a part of the World Health Organization (WHO) – which stated that “the herbicide glyphosate is probably carcinogenic to humans” in its latest expert assessment in March 2015.

However, there are still no conclusive studies which directly link normal exposure to glyphosate with cancers in humans – results based on animal studies do not always correlate with human studies.

But the IARC statement is something to be wary about, especially if you use glyphosate when working in your garden.

And whatever you eat, always wash your greens and grains very thoroughly before use. Although I am not squeamish or paranoid, let’s just say that if I was sharing a flat with a biochemist, I won’t be eating anything he’s left in the fridge.

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