Poisons in our food

Poison is in everything, and no thing is without poison. The dosage makes it either a poison or a remedy. – Paracelsus

I had a conversation on Twitter a while ago about genetically engineered crops. One of the last tweets said, “It’s not the genetically modified food that worries me … it’s the poisoning of crops.”

The zeitgeist on genetic engineering

This comes up frequently in discussions on Twitter, on this blog, on the radio, in the media, and with people in conversation. The tweet on the right shows this general feeling.

Science doesn’t just show that most genetically engineered food is safe, it shows that all genetically engineered food currently grown for the public is as safe as (and in some cases, safer than) non-GE food equivalents (that is, an apple to apple comparison). The National Research Council says, “Genetic engineering is one of the newer technologies available to produce desirable traits in plants and animals used for food, but it [GE] poses no unique health risks that cannot also arise from conventional breeding and other genetic alteration methods.” [my emphasis]

Herbicides in Food

Let’s look at the first worry listed in the tweet on the right side of the page: Herbicides introduced into foods.

There aren’t any.

No herbicides have been placed in any plant via genetic engineering. None. Zip. Nada. No GE plant has an herbicide inside it. But if an herbicide had been, that would not affect animals, such as you and me. We are not plants.

Plant scientists have made certain crops resistant to certain herbicides. Herbicide resistance is sometimes shortened to simply HR (or RR for RoundUp Ready). HR is not the same as placing herbicide in a plant.

Resistance is Natural

As any farmer will tell you, resistance to any herbicide, insecticide, fungicide, etc., occurs over time as some targeted pests will survive. Those survivors will be able to pass along their genes to their offspring

There are HR crops in the market that have been developed by standard breeding or genetic engineering techniques. Just because the plant is herbicide resistant does not mean it was genetically engineered.

The upshot is that glyphosate is a separate topic from HR crops altogether.

The most common herbicide resistance is to Monsanto’s RoundUp (active ingredient: glyphosate) which is now off patent and manufactured by several companies. Certain plants can have natural resistance to glyphosate. Conifers are not at all bothered by glyphosate. One of Monsanto’s early sales pitches was to foresters. RoundUp was much more benign than 2,4-D and 2,4,5-T.

To speed up the process, plant scientists found a glyphosate-resistant gene in another plant and put it into a plant they desired to have the glyphosate-resistant trait. The most common HR trait for crops on the market is to glyphosate-based herbicides, e.g., RoundUp, so-called RoundUp Ready (RR) crops.

So resistance to pesticides (herbicide is a pesticide) is a natural occurrence. It was possible that the crops could have been sprayed with herbicides and those plants showing some resistance to the spray could have been selected and bred to produce HR plants.

Insecticides in our Food

Bt Corn, Bt soy, Bt Sugar Beets, Bt Potatoes, and Bt Canola

When insecticide inside our food is mentioned (not counting the 99.99% which is produced naturally by the plant), Bt, Bacillus thuringiensis is what is meant.

Bacillus thuringiensis (Bt) is a soil bacterium that forms spores during the stationary phase of its growth cycle. The spores contain crystals, predominantly comprising one or more Cry and/or Cyt proteins that have potent and specific insecticidal activity. Different strains of Bt produce different types of toxin, each of which affects a narrow taxonomic group of insects. (Sanahuja, et. al. 2011)

According to Ric Bessin, Extension Entomologist at the University of Kentucky College of Agriculture, when the target insect eats a part of the plant that contains the Bt protein, “the protein binds to the gut wall and the insect stops feeding. Within hours, the gut wall breaks down and normal gut bacteria invade the body cavity. The insect dies of septicaemia as bacteria multiply in the blood.” This protein targets specific insects. Bessin points out that, “Even among Lepidoptera larvae, species differ in sensitivity to the Bt protein.”

The level of risk of these gene products to consumers and those involved in food production can be and is evaluated by standard toxicological methods. The toxicology testing for the Bt endotoxins typifies this approach and has been described in detail by the U.S. EPA (1998, U.S. EPA (2001). The safety of most Bt toxins is assured by their easy digestibility as well as by their lack of intrinsic activity in mammalian systems (Betz et al., 2000; Kuiper et al., 2001; Siegel, 2001). In this case, the good understanding of the mechanism of action of Bt toxins, and the selective nature of their biochemical effects on insect systems, increases the degree of certainty of the safety evaluations….The toxic properties of Bt endotoxins to both target and nontarget species of many kinds are well known (Betz et al., 2000). They show a narrow range of toxicity limited to specific groups of insects, primarily Lepidoptera, Coleoptera, or Diptera, depending on the Bt strain. Nevertheless, Bt-producing plants have been tested broadly to determine whether any alteration in this limited spectrum of toxicity has occurred, without the discovery of any unexpected results (see Gatehouse et al., 2002; Lozzia et al., 1998; Orr and Landis, 1997; and Pilcher et al., 1997 for examples of such studies). Exotoxins and enterotoxins, which are much more broadly toxic than the endotoxins, are also produced by some Bt strains, but these are not present in the transformed plant, because their genes are not transferred into the crop. (Toxicological Sciences. 2003) [Emphasis added]

The toxic properties of the Cry and/or Cyt proteins produced “show a narrow range of toxicity limited to specific groups of insects, primarily Lepidoptera, Coleoptera, or Diptera” and even this toxicity to those species is further limited by the Bt strain.

That boils down to the Bt proteins are just proteins to your gut and will be used as any other protein is by your body.


Bt-Corn: What It Is and How It Works | Entomology.” 2016. Accessed April 28. https://entomology.ca.uky.edu/ef130.

Sanahuja, Georgina, Raviraj Banakar, Richard M Twyman, Teresa Capell, and Paul Christou. 2011. “Bacillus Thuringiensis: A Century of Research, Development and Commercial Applications.” Plant Biotechnology Journal 9 (3): 283–300. doi:10.1111/j.1467-7652.2011.00595.x.

Toxicological Sciences . 2003. “The Safety of Genetically Modified Foods Produced through Biotechnology” 71 (1 ): 2–8. doi:10.1093/toxsci/71.1.2 .

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