Preventive Medicine Column

Dr. David L. Katz

I appreciate that the term “genetically modified”- as in genetically modified organisms (GMO) or genetically modified food (GMF)- conjures images of Frankenstein’s monster (or at least, Frankenstein’s monster’s lunch), and makes people freak out.  The truth, though, is that “genetic modification” has been with us for a long time, and it isn’t all bad- although it can certainly can be.

I have two dogs, Bramble and Zouzou.  I love them, they love me.  And they are, undeniably…genetically modified.

Every dog that isn’t a wolf is genetically modified through a process better known as breeding.  Breeding- or more specifically, selective breeding- is the controlled mating of individual members of a species to get the right combination of genes into their offspring.  While the process may not involve test tubes, its effects are as dramatic and profound as anything a laboratory could cook up.  Genetic modification through the process of selective breeding has turned wolves into Chow Chows, and Chihuahuas.

If you have cats that aren’t ocelots, they, too, are the product of willful, genetic modification.  As are our horses, goats, chicken, sheep, and cattle.  And that list gets us into the realm of food.  The domestic chicken and cattle many of us eat are the product of many generations of selective breeding, i.e., genetic modification.

Virtually every plant food we eat, too, is a product of selective breeding at least, and often, more active manipulation of genes as well.  In fact, Mendel- the father of modern genetics– revealed to us all the existence of genes by…modifying them.  Mendel famously cross-bred pea plants to show how their traits were passed along to the next generation.  So in the 1850s, we had, in essence, genetically modified peas.

Tomatoes, Romaine lettuce, pineapple, corn, watermelon, and almost all other modern produce have their origins in nature, of course, but as eaten today are decidedly products of careful, selective breeding.  Seedless grapes are a product of willful genetic modification.  Nectarines are the result of careful culling of a recessive gene in peaches that eliminates their eponymous fuzzy skin.  Ever try a tangelo?  It is the hybrid offspring of a tangerine and grapefruit.  Genetic modification, to be sure.

Then there is the ultimate defense of genetic modification.  In a word: sex.

While most of us tend to take sex for granted (I mean, we take for granted the fact that there IS sex), scientists studying evolutionary biology do not.  They have wrestled with the question: why does sexual reproduction exist at all?  After all, it involves a great deal of trouble- the obvious elements of which include finding, wooing, and often competing for a mate.  Asexual reproduction is a whole lot easier.

The conclusion reached by experts is that the principal reason sex exists at all is: genetic modification.  Sex mixes the genes of one parent with the genes of another to produce a genetically modified product we might be inclined to call…a child.  Or pup.  Or cub.  Or piglet.

With asexual reproduction, genetic mutations simply add up over time.  Eventually, they reach a concentration where they threaten survival, either by making organisms dysfunctional, or by rendering them very vulnerable to some environmental challenge.  In contrast, sexual reproduction dilutes the effects of such mutations every generation. 

Modern methods of genetic modification, however, differ not just in degree, but in kind, from the time-honored approaches of selective breeding.  Part of what defines a species is that its members can mate and produce offspring only with one another.  The willful introduction of genes from bacteria, or amphibians (a gene for an anti-freeze like compound enables fish and frogs to survive through bitter cold, and could be used in crops to make them resistant to a sudden frost), into produce is not business as usual.  It has the potential to introduce new proteins, and new combinations of proteins, into the food supply.

The potential consequences of this are likely to include, but not limited to: food allergies, food sensitivities and intolerance, and auto-immune diseases.  Concerns extend to infertility, and cancer. High rates of fatigue, attention deficit disorder, gluten intolerance, chronic pain, irritable bowel syndrome, and affective disorders may all relate in part to our manipulation of the food supply.

But we can’t let it go at that, because by one means or another, almost our entire food supply is already the product of genetic modification.  We are now a global population of 7 billion and rising, and in the absence of genetically modified crops, we would already be unable to feed ourselves.

Genetic modification has the potential to make crops resistant to frost, and produce resistant to spoilage- thereby lowering costs, and increasing availability.  Genes that make crops pest resistant could mean less use of pesticides, with benefits for human health and the environment alike.

So, genetically modified foods can be, and almost certainly already are in some cases, overtly harmful.  Abandoning genetic modification of foods, however, is impractical, if not impossible.  It, too, could result in harms- and missed opportunities.

Genetic modification is means- some versions are new, and others are as ancient as sex itself.  It is the ends we must judge, on a case-by-case basis.




Dr. David L. Katz;