The possibility that we might see an increase in the
number of allergic reactions to food as a result of
genetic engineering has a powerful emotional appeal.
Parents of a severely allergic child, already conditioned
to scrutinize food labels and to watch for warning symptoms,
are understandably concerned that an additional and
unpredictable danger may have been introduced into the
food they buy. Even people who have never experienced
an allergic reaction may worry that they are being exposed
to new substances for which there is little track record
of safety or harm.
|However, there is no evidence so far that genetically
engineered foods are more likely to cause allergic
reactions than are conventional foods. The genetic
engineering process itself does not create allergens.
The nature of the genes that are chosen for transfer
will determine whether allergens are introduced
into the engineered host plant. The Food and Drug
Administration reviews proposed transgenic foods
and compares possible allergens to a checklist of
characteristics that have been found to be associated
with allergenicity. In several years of testing
dozens of proposed transgenic crops, only two potential
problems have been uncovered: a soybean that was
withdrawn from development and the now-famous StarLink
The soybean, developed by Pioneer Hi-Bred, was modified
by the introduction of a gene from the Brazil nut. The
intention was to improve the nutritional quality of
the soybean by adding the amino acid methionine, which
is low in soybean and abundant in the Brazil nut. Because
allergies to nuts are common, the use of a nut as the
donor of the transgene raised eyebrows among regulators.
The transgenic soybean was tested (Nordlee
et al., 1996) and people who had allergic reactions
to Brazil nuts also had allergic reactions to the genetically
engineered soybean. It appeared that the gene chosen
to improve nutritional quality was one of the genes
that trigger allergic reactions. Pioneer had intended
to market the soybean only for animal feed, but the
difficulty of keeping animal feed separate from human
food during harvesting, transport, and storage became
a consideration. Pioneer decided not to ask for approval
to market the soybean. It was never approved by the
government and was never grown commercially or sold
in stores. More information on this is available at
by the company Aventis, was originally intended to be
sold as an all-purpose corn, but concern that it might
be allergenic led to its approval only for animal feed.
Although the 2001 finding is that StarLink corn is probably
not allergenic, the scientific debate continues, with
a panel of experts still unable to reach a consensus
about the adequacy of the evidence. Some of the points
of debate are presented below.
- Data provided
by Aventis suggested that StarLink protein was degraded
by wetting and heating, so that commercially processed
foods and foods prepared in the home by mixing and
baking would contain only low levels of the intact
protein. The advisory panel suggested that higher
levels of the protein might still be present and capable
of causing allergic reactions, but might be undetectable
via current tests, if wetting and heating changed
the shape of the molecule.
the Centers for Disease Control and Prevention did
not find evidence that the StarLink protein had caused
allergic reactions in people who reported adverse
health effects from eating corn-based products, the
scientists on the panel said the CDC's test might
not be sufficiently sensitive.
have not reported seeing cases of possible allergenicity
to StarLink corn. But the panel members suggested
that the government should be more aggressive in collecting
information about cases that may have gone unreported.
an interest in this issue are encouraged to review the
by the FDA's panel of independent scientists concerning
the validity of the tests.
issue of allegenicity remains unresolved, the panel
noted that the government's estimate in early 2001 of
about 0.4% StarLink in the nation's human food supply
of corn was probably an overestimate and that aggressive
actions by the government and by Aventis had reduced
the amount to less than 0.125% by the summer of 2001.
Testing for allergenicity is a complex process that
utilizes both test-tube reactions and responses in live
subjects. People and animals can be used as live subjects,
and researchers are considering various animals, including
rats, dogs, pigs, guinea pigs, and mice, that might
serve as useful substitutes for tests on people. Animals
may not always be good predictors of human allergic
reactions. Before the research on the Brazil nut soybean
et al., 1996), other researchers (Melo
et al., 1994) had tested the same Brazil nut protein
in rats and mice and decided that it was not a major
allergen. Improvements in testing for allergens will
probably be spurred by the increased demand for such
testing in genetically engineered crops.
Just as some
people every year discover that they have developed
an allergy to common foods such as wheat or eggs, or
to newly popular foods such as kiwifruit, some people
may develop allergies to transgenic foods despite regulatory
efforts to weed out potential problems. This is undeniably
serious for people who develop allergic responses, but
there is currently no evidence that transgenic foods
pose more of a risk than conventional foods do.
More information about allergenicity in transgenic
foods is available from the Pew Initiative on Food and
Biotechnology at http://pewagbiotech.org/buzz/display.php3?StoryID=12
and from the Royal Society's 2002 report "Genetically
modified plants for food use and human health--an update"