Genetically
Modified Foods
For thousands of
years, humans have been genetically enhancing other organisms through the
practice of selective breeding. Our
ability to manipulate plants by introducing new genes promises innovative
solutions to many real-world problems. Yet there is considerable opposition to
the use of genetically modified plants for food production and other uses.
Genetic engineering offers a time-saving method for producing larger,
higher-quality crops with less effort and expense. Yet such benefits must be
balanced against the risks of changing the genetic makeup of organisms. Genetically
modified organisms (GMOs) can be defined as organisms (i.e. plants, animals or
microorganisms) in which the genetic material (DNA) has been altered in a way
that does not occur naturally by mating and/or natural recombination. The
technology is often called “modern biotechnology” or “gene technology”,
sometimes also “recombinant DNA technology” or “genetic engineering”. It allows
selected individual genes to be transferred from one organism into another,
also between nonrelated species. Foods produced from or using GM organisms are
often referred to as GM foods.
GM foods are
developed and marketed, because there is some perceived advantage either to the
producer or consumer of these foods, which is meant to translate into a product
with a lower price, greater benefit (in terms of durability or nutritional
value) or both. Initially GM seed developers wanted their products to be
accepted by producers and have concentrated on innovations that bring direct
benefit to farmers and the food industry generally. One of the objectives for
developing plants based on GM organisms is to improve crop protection. The GM
crops currently on the market are mainly aimed at an increased level of crop
protection through the introduction of resistance against plant diseases caused
by insects or viruses or through increased tolerance towards herbicides.
Benefits
of GM Foods
In BT Corn, resistance
against insects is achieved by incorporating a specific gene from the bacterium
Bacillus thuringiensis (Bt) which produce toxin against insects. This toxin is
currently used as a conventional insecticide in agriculture and is safe for
human consumption. The GM crops inherently produce this toxin have been shown
to require lower quantities of insecticides in specific situations, e.g. where
pest pressure is high. Virus resistance is achieved through the introduction of
a gene from certain viruses which cause disease in plants. Virus resistance
makes plants less susceptible to diseases caused by such viruses, resulting in
higher crop yields. Herbicide tolerance is achieved through the introduction of
a gene from a bacterium conveying resistance to some herbicides. In situations
where weed pressure is high, the use of such crops has resulted in a reduction
in the quantity of the herbicides used.
The release of GMOs
into the environment and the marketing of GM foods have resulted in a public
debate in many parts of the world. This debate is likely to continue, probably
in the broader context of other uses of biotechnology (e.g. in human medicine)
and their consequences for human societies. Even though the issues under debate
are usually very similar (costs and benefits, safety issues), the outcome of
the debate differs from country to country. On issues such as labelling and
traceability of GM foods as a way to address consumer preferences, there is no
worldwide consensus to date. Despite the lack of consensus on these topics, the
Codex Alimentarius Commission has made significant progress and developed Codex
texts relevant to labelling of foods derived from modern biotechnology in 2011
to ensure consistency on any approach on labelling implemented by Codex members
with already adopted Codex provisions.
Standard
Practices
Generally, consumers consider that
conventional foods (that have an established record of safe consumption over
the history) are safe. Whenever novel varieties of organisms for food use are
developed using the traditional breeding methods that had existed before the
introduction of gene technology, some of the characteristics of organisms may
be altered, either in a positive or a negative way. National food authorities
may be called upon to examine the safety of such conventional foods obtained
from novel varieties of organisms, but this is not always the case. In
contrast, most national authorities consider that specific assessments are
necessary for GM foods. Specific systems have been set up for the rigorous
evaluation of GM organisms and GM foods relative to both human health and the
environment. However, similar evaluations are generally not performed for
conventional foods. Hence, currently there exists a significant difference in
the evaluation process prior to marketing for these two groups of food. The WHO
Department of Food Safety and Zoonoses aims at assisting national authorities
in the identification of foods that should be subject to risk assessment and to
recommend appropriate approaches to safety assessment. Should national
authorities decide to conduct safety assessment of GM organisms, WHO recommends
the use of Codex Alimentarius guidelines.
The safety
assessment of GM foods generally focuses on:
(a) Direct health
effects (toxicity);
(b) Potential to
provoke allergic reaction (allergenicity);
(c) Specific
components thought to have nutritional or toxic properties;
(d) The stability
of the inserted gene;
(e) Nutritional
effects associated with genetic modification;
(f) Any unintended
effects which could result from the gene insertion.
Major
Issues of Concern for Human Health
While theoretical
discussions have covered a broad range of aspects, the three main issues
debated are the potentials to provoke allergic reaction (allergenicity), gene
transfer and outcrossing.
Allergenicity
Many people suffer
from allergies to various food items, including nuts, wheat, eggs, or dairy
products. There is a concern that the protein products of introduced genes may
be toxic or allergenic to certain individuals. As a matter of principle, the
transfers of genes from commonly allergenic organisms to non-allergic organisms
are discouraged unless it can be demonstrated that the protein product of the
transferred gene is not allergenic. While foods developed using traditional
breeding methods are not generally tested for allergenicity, protocols for the
testing of GM foods have been evaluated by the Food and Agriculture
Organization of the United Nations (FAO) and WHO. No allergic effects have been
found relative to GM foods currently on the market.
Gene Transfer
Gene transfer from
GM foods to cells of the body or to bacteria in the gastrointestinal tract
would cause concern if the transferred genetic material adversely affects human
health. This would be particularly relevant if antibiotic resistance genes,
used as markers when creating GMOs, were to be transferred. Although the
probability of transfer is low, the use of gene transfer technology that does
not involve antibiotic resistance genes is encouraged.
Outcrossing
The migration of
genes from GM plants into conventional crops or related species in the wild
(referred to as “outcrossing”), as well as the mixing of crops derived from
conventional seeds with GM crops, may have an indirect effect on food safety
and food security. As a primary concern, preventing GM versions from mixing
with the naturally existing populations of plants from which they're derived is
recommended. Because, plants rely on the transfer of pollen, via insects or the
air, to breed and produce offspring, and it's difficult to control how they
cross-breed in the wild. Cases have been reported where GM crops approved for
animal feed or industrial use were detected at low levels in the products
intended for human consumption. In most cases, it's not yet clear how
introduction of the non-native gene would affect wild populations. However, several
countries have adopted strategies to reduce mixing, including a clear
separation of the fields within which GM crops and conventional crops are
grown.
Different GM
organisms include different genes inserted in different ways, which means that
individual GM foods and their safety should be assessed on a case-by-case
basis, where it is not possible to make general statements on the safety of all
GM foods. GM foods currently available on the international market have passed
safety assessments which are not likely to present risks for human health. In
addition, no effects on human health have been shown as a result of the
consumption of such foods by the general population in the countries where they
have been approved. Continuous application of safety assessments based on the
Codex Alimentarius principles and, where appropriate, adequate post market
monitoring, should form the basis for ensuring the safety of GM foods.
When farmers start
growing genetically modified crops, they stop growing the old varieties, where
these old varieties are important sources of diverse genes that give plants
other desirable characteristics. For example, a new pest or disease could come
along and destroy the genetically modified rice. If one of the old rice
varieties has a gene that makes it resistant, it could be cross-bred to make
the saltwater rice resistant as well. If we lose the old varieties, we also
lose their useful genes.
