One of the most contentious issues surrounding the controversy about genetically engineered (GE) foods is whether there may be long-term safety risks, and whether current regulations are sufficient to prevent such risks from occurring.
As I briefly discussed in my last post, major science organizations have said that some GE foods produced by current methods could be harmful, and have provided some examples of the kinds of harm that might occur.
The current situation
Most corn, soybeans, and cotton in the U.S. are engineered to contain one or several genes for insect or herbicide resistance. Many more types of engineered genes are in the works. Photo by danellesheree.
No long-term safety tests in animals are required by any regulatory agency. In some circumstances, 90-day, so-called sub-chronic tests may be required in Europe. But 90 days is far short of the one to two years that usually satisfy long-term safety test requirements.
Long-term experiments are required for products like drugs and chemical pesticides, and sometimes for food additives. They are considered important or necessary for determining harm that may take years to develop, such as cancers, Parkinson’s disease, and so on.
Recently, the American Association for the Advancement of Science (AAAS) Board of Directors cited a review of several long-term and multi-generational studies by Snell and colleagues in support of their claim that GE foods are safe and well tested.
The study cited by the AAAS Board has made the rounds in recent months, being used to claim that long-term studies show that GE is safe, and that shorter-term tests are sufficient.
The study authors extrapolate from the reviewed research that GE crops can be safely used in foods, based on currently required tests. For example, at the end of the paper’s abstract they write: “The studies reviewed present evidence to show that GM plants are nutritionally equivalent to their non-GM counterparts and can be safely used in food and feed.” They also conclude that 90-day tests are usually sufficient, and even these may not always be needed.
The study makes some useful contributions, but a careful reading shows that it contains some serious flaws. These limitations — some of which involve the interpretation of the results by the authors — eliminate the value of this study for drawing general conclusions about the safety of GE foods, or the adequacy of current shorter tests to reveal long-term risks from engineered foods.
Missing the fundamentals
The most glaring limitation is that regardless of the findings, generalization about safety and testing of GE crops is not scientifically justified based on the review of several studies.
The safety of the very few currently available engineered traits and foods is not the only issue. There are many novel engineered genes in the pipeline, coding for a plethora of traits, from pest resistance to drought tolerance, to nutritional alterations and industrial products.
We therefore depend on the regulation of engineered traits to ensure the safety of all GE foods — current and future. We must therefore consider whether our regulations are adequate for current and future GE crops and foods.
This is important because most scientists on all sides of the debate about GE safety agree that the risk of each crop and gene combination must be considered on its own merits. In other words, just because one, or ten, or even one hundred genes are shown to be safe does not assure the safety of the next one.
This is easy to understand if we consider the wide range of functions that genes affect — virtually everything that an organism is composed of. Take a Brazil nut tree, for example. The majority of genes code for harmless things like enzymes that make sugars or amino acids in the plant, or make the chlorophyll involved in capturing light energy. But, as I have noted before, one gene also codes for the major allergen from Brazil nuts, which was unsuspectingly engineered into soybeans (and never commercialized), and which can be deadly if consumed by some sensitive people.
One could run safety tests of all of those genes that code for benign functions in the Brazil nut, and according to the review study thereby conclude that, based on current tests, GE foods can be safely used. But what if the next engineered gene was the major Brazil nut allergen? Would this broad conclusion still be valid? Certainly not.
There are obviously harmful genes (or groups of genes) from non-food plants and other organisms that we know about and would therefore avoid engineering into foods, such as the insecticide nicotine produced by tobacco, or the insecticide rotenone, produced by the roots of several tropical plants.
These are generally understood, and therefore avoidable. Rotenone is a particularly interesting example, because it has relatively low immediate (acute) toxicity in mammals, but has been implicated for its possible connection with Parkinson’s disease, which usually occurs later in life, and which was not understood until recently.
These are also extreme examples. But like most phenomena in biology, there are likely to be a range of possible health effects that genes can produce, from innocuous to extreme, and including those that are intermediate and not easily predicable or detectable with short-term tests.
Less fundamental, but important, is that the number of genes reviewed in the Snell paper is actually very small, and not representative of what may be put into crops in coming years. Of the dozen long-term studies reviewed, 10 tested the gene for glyphosate herbicide resistance (EPSPS) in soybeans, one was a Bt insecticidal gene in corn, and one a cedar pollen gene in rice.
Even if generalizations about safety were possible, that is a tiny representation of the possibly hundreds of genes that may be used in coming years, and virtually meaningless for drawing general conclusions.
For the dozen multi-generational studies, six tested Bt in corn, three were for glyphosate in soybeans, two for another herbicide resistance gene (glufosinate) in the grain triticale, and one for a similar gene in potato. This is not likely to be representative of engineered genes or crops in coming years.
For these reasons alone, the Snell paper says little about the safety of GE foods generally, or the need for long-term testing. It is therefore misleading to use the study to make broad claims that GE foods are safe based on existing long-term tests in animals, or, as the AAAS Board claimed, are equivalent to their non-GE counterparts.
But there is more, and in my next post I will discuss specific limitations of the Snell research, including why it does not demonstrate that short-term or 90-day studies are generally sufficient to determine the safety of engineered genes.