GM foods: popular myths

When it comes to the truth about genetically modified foods, it's difficult to know what to believe. DietDoc takes a look at some of the most persistent myths.

The information for the article has been sourced from a report based on a publication released by the New Zealand Royal Commission on genetic modification. This report was the result of 14 months of consultation with proponents and opponents of GM.

The Commission functioned as an independent review panel created to report to the New Zealand government on the options available to deal with GM. This report represents the first of its kind in the world.

Among many other aspects, the Commission examined some of the most popular myths relating to GM and investigated the actual facts:

Myth: "GM potatoes had toxic effects on rats that may also affect humans"
Dr Arpad Pusztai, a senior scientist at the Rowett Institute in Aberdeen, Scotland caused consternation when he announced to the media that rats eating GM potatoes suffered from depressed immunity and experienced changes in the structural lining of their intestinal tracts.

Investigation showed that the rats in the trial conducted by Dr Pusztai had been fed raw potatoes. Since rats don't like to eat raw potato, they stopped eating and the trial had to be abandoned after 67 days because the rats were starving.

Starvation is known to alter the intestinal lining and both the rats fed raw GM potatoes and those fed raw standard potatoes had similar changes in their intestines. The Commission also pointed out that other potato toxins found in raw potatoes could have caused the changes. In addition, the tests that Dr Pusztai had used to test immunity in the rats were not standard, accepted tests.

The Commission concluded that, "Within the scientific community there is general agreement that the results of Dr Pusztai's experiment are inconclusive insofar as there were flaws in the process and the project was incomplete. Extensive testing carried out by Chinese researchers, similar to that described by Dr Pusztai and Ewen, has not replicated their results."

Myth: "L-tryptophan produced from GM bacteria caused death of humans in the US"
In the 1980s, L-tryptophan, an amino acid that is found in proteins, became a popular treatment for insomnia and depression. This amino acid is usually produced with tryptophan-producing bacteria via fermentation. The bacteria used for such fermentations can either be standard bacteria or GM bacteria.

In 1989, individuals using L-tryptophan in high doses started to develop eosinophilia-myalgia syndrome (EMS), a new illness associated with painful, swollen muscles, rashes, digestive problems and increased white blood cell counts. Thirty-seven people died in the USA, 1500 were disabled and about 5000 were affected.

Intensive investigation found that the Showa Denko company, which produced the L-tryptophan that caused these harmful effects, were using GM bacteria for their fermentation process. However, of greater importance is the fact that this company had started using a different purification process that utilised less charcoal than normal to clean the L-tryptophan.

When the L-tryptophan produced by the Showa Denko company was analysed, 60 contaminants were identified, of which six were responsible for causing EMS. These six toxins were identified as the agents that caused EMS and their presence in the L-tryptophan was due to an inefficient purification process, not the use of GM bacteria in the fermentation process.

The Commission concluded, "The United States courts decided that the manufacturing process rather than genetic modification was at fault".

Other tryptophan products were available on the market that had been produced by GM bacteria and these did not cause any health problems.

Myth: "The increase in phyto-oestrogen levels in herbicide-tolerant soybeans can cause breast cancer"
In Switzerland, the Basle Appeal Against Genetic Engineering published a letter in February 1997 in which they stated, "We fear that the Roundup Ready soybean produces large quantities of pseudo-oestrogens when it is sprayed with Roundup herbicide. Today, it is assumed that oestrogen hormones play an important role in the emergence of breast cancer."

It is a well-known fact that soya beans contain compounds called phyto-oestrogens and that these compounds can have both positive and negative effects on human health.

Investigations found that the study the Swiss anti-GM group were basing their evidence on had been carried out in 1988 – at which time the Roundup Ready soybeans did not exist!

The Commission concluded, "Some plant-protection agents contain pseudo-oestrogens although Roundup herbicide, by contrast, contains none at all. This fact has been confirmed by the Freiburg Ecological Institute."

Myth: "Bt corn threatens the existence of Monarch butterfly populations"
GM has been used to produce Bt-corn (maize), which is toxic to corn borer, an insect pest that is a member of the Lepidoptera family. Moths and butterflies, such as the Monarch, are also members of the Lepidoptera family and Bt-corn strains are thus also toxic to these insects.

The larvae of Monarch butterflies feed exclusively on the leaves of milkweed plants, which are commonly found in and around cornfields. Pollen from nearby corn can theoretically be blown onto the leaves of the milkweed and eaten by the Monarch larvae.

Because there has been a decline in the Monarch populations in recent years, the GM corn crop was blamed.

Intensive investigations showed that there is no overlap in the breeding time of the butterfly and the time when pollen is shed by the corn. In addition, it was found that any Bt effect was restricted to an area of 5 metres surrounding the cornfields and that this occurred very rarely.

The Commission deduced that, "These findings indicate that, outside cornfields, Monarch larvae exposure to Bt-corn pollen is minimal, and that, within fields, Monarchs will have a low probability of encountering a toxic level of pollen. The report also suggests that the elimination of pesticides through the use of Bt-corn can be beneficial to Monarch butterfly populations, and concludes that there is not sufficient evidence to support the belief that there is significant risk to Monarch butterflies from Bt-corn use."

These examples of GM myths, and the actual scientific facts that disprove the myths, are just a small sample of the many instances in which the media or the anti-GM lobby have instigated scare stories to frighten the public and discredit GM foods.

There are many other examples, but if the Royal Commission of New Zealand were able to conclude that these ideas and stories are myths and not facts, then it should help the public to view GM food scare stories in a sensible light.

- (Dr IV van Heerden, DietDoc, June 2010)

We live in a world where facts and fiction get blurred
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