As a health care provider and daughter-in-law to a plant biologist, I hear a variety of conflicting things about the genetic modification of plants, and its impact on our health. I have become increasingly concerned about how genetic modification affects our food supply and how this affects our health and the health of our planet.
Genetic modification has been around for centuries in the form of “natural selection” and “selective breeding”. Anyone who took high school biology will remember the charts about genetics and how the mother and father contribute genes to the child, resulting in things like eye color and hair color. A similar thing happens in plants leading to impatiens of red and white coming from a planter box of pink. A certain degree of genetic selection happens in nature and leads to a fabulous variability in plants and animals. For centuries farmers have saved the seeds from the strongest plants or the ones which produce the most flavorful tomatoes, and planted those seeds the following year, gradually allowing for “natural” selection of the plant qualities leading to the best outcome for the farmer.
Since the mid-1990s there has been a new trend in genetic modification of plants. Rather than choosing the naturally- occurring mutations which suit our needs, scientists began to insert and delete sequences from plant genes to increase the amount of omega-3 fatty acids in pork, make corn resistant to certain bacteria, allow certain herbicides to be used on a crop without killing the plant the farmer is trying to grow, improve the shelf life of tomatoes, and other things.
According to Wikipedia, genetic modification is defined as “the insertion or deletion of genes.” There are two main ways to genetically modify something. In the process of cisgenesis, genes are artificially transferred between organisms that could be conventionally bred. In the process of transgenesis, genes from a different species are inserted, which is a form of horizontal gene transfer. In nature this can occur when exogenous DNA (DNA from an outside source) penetrates a cell membrane for any reason. To do this artificially can require attaching the genes to a virus or just physically inserting the extra DNA into the nucleus of the intended host with a very small syringe, or with very small particles fired from a gene gun.
The first commercially-grown genetically modified whole food crop was a tomato (called FlavrSavr), which was modified to ripen without softening. This product never really caught on and became profitable, so it was only available for a few years to a limited market. Several companies have now genetically modified a variety of plants including soybeans, corn, cotton, sugar cane, sugar beets, Hawaiian papaya, and rapeseed. Over the last 10 years these have become widely distributed into our food supply. Genetically modified soybeans carry herbicide-tolerant traits only, but corn and cotton carry both herbicide tolerance and insect protection traits (the latter largely the Bacillus thuringiensis Bt insecticidal protein). From 2002 to 2006, there were significant increases in the planted area of Bt-protected cotton and corn, and the number of sown acres of herbicide tolerant corn also increased. By 2006, 89% of the planted area of soybeans, 83% of cotton, and 61% of corn in the US were genetically modified varieties. back to top
The Good, the Bad, and the Ugly
Proponents of genetically-modified foods say that these crops are beneficial because they are more resistant to certain bacteria and fungi, and are resistant to the effects of certain herbicides. This is believed to result in higher yield, leading to increased food supply. They indicate that no studies have demonstrated that these products are harmful in any way, and swear that genetically modified foods are the answer to the world’s hunger problems.
Stronger plants, higher yields, more ability to use herbicides without harming your cash crop - sounds pretty good. So, what’s the problem?
Opponents of GMO foods say the American people are being used as unknowing subjects in a giant science experiment which reflects the ultimate in corporate greed and corruption. Although little research performed in the US has demonstrated any problems with GMO products, there has been precious little research performed and much of it was funded by the manufacturers of the GMO products. Outside the US, the research presents a very different picture about the safety of GMO foods. Consumption of these products is being linked to declines in fertility, gut disturbances, liver and kidney problems, food sensitivities, metabolic disorder, cancers, and other health issues. back to top
A study by Charles Benbrook, Chief Scientist of the Organic Center, found that genetically engineered Roundup-Ready soybeans do not increase yields (2). The report reviewed over 8,200 university trials in 1998 and found that Roundup Ready soybeans yielded 7-10% less than similar natural varieties. In addition, the same study found that farmers used 5-10 times more herbicide (Roundup) on Roundup Ready soybeans than on conventional ones.
In 2010 three scientists published a statistical re-analysis of three feeding trials that had previously been published by others as establishing the safety of genetically modified corn. (7, 8, 9) The new article claimed that their statistics instead showed that the three patented crops (Mon 810, Mon 863, and NK 603) cause liver, kidney, and heart damage in mammals.
A 2009 study published in the International Journal of Biological Sciences, (9) details the toxicity of three genetically modified corns. Researchers from Committee for Independent Research and Information on Genetic Engineering (CRIIGEN) and Universities of Caen and Rouen have highlighted a number of negative effects linked with their consumption. They concluded: “Our analysis clearly reveals for the 3 GMOs new side effects linked with GM maize consumption, which were sex- and often dose-dependent. Effects were mostly associated with the kidney and liver, the dietary detoxifying organs, although different between the 3 GMOs. Other effects were also noticed in the heart, adrenal glands, spleen and hematopoietic system. We conclude that these data highlight signs of hepatorenal toxicity, possibly due to the new pesticides specific to each GM corn. In addition, unintended direct or indirect metabolic consequences of the genetic modification cannot be excluded.”
Italy’s National Institute of Research on Food and Nutrition recently published a report online in the Journal of Agricultural FoodChemistry (3) documenting significant disturbances in the immune system of young and old mice that have been fed the genetically modified corn MON 810. Increases in inflammatory cytokines were found in the guts of the mice which had been fed the GMO corn, but not in the ones fed non-GMO corn.
Yet another study, published in the journal Toxicology in 2009, (5) demonstrated that glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines. Round-up, one of the most commonly used herbicides, is a glyphosate-based herbicide manufactured by the same company which produces many of the GMO seeds used in the US.
Another recent study found that honey bees fed on the active form of purified Cry1Ab protein, the genetically modified protein found in GMO Bt corn, can be affected in the learning responses necessary to associate nectar sources with odorants.A study led by Dr. Jürgen Zentek, Professor of Veterinary Medicine at the University of Vienna showed that mice fed a genetically-engineered corn diet had fewer litters, fewer total offspring, smaller offspring, and more females with no offspring, than mice fed the conventional corn. The effects were particularly pronounced in the third and fourth litters, after the mice had consumed the GMO corn for a longer period of time. (10)
Despite assertions from the manufacturers and the FDA that GMO foods are safe, these studies suggest there is reason for concern. The bottom line is that scientists are altering the genetic structure of foods without clear understanding of how this alters the nutrition of the food, the effect of the new genetic structure on the ecosystem the food is grown in, or how the altered genetic structure truly affects the animals (including humans) which consume the plant. These genetic alterations created in a laboratory occur much faster than a “natural selection” model (the plants naturally produce variations, and the seeds from the "preferred" variation are selected for the next crop) would allow for, and without a concomitant genetic changes to the digestive tracts and metabolism of the eaters. My advice is to avoid consuming GMO “foods” until we have a clear understanding of how the genetic alteration affects the food and how that in turn affects us.
As noted earlier, a huge percentage of the soybeans, cotton (cotton seed oil), corn, and rapeseed (canola oil) grown in the US are now GMO crops. Corn, soybean oil, canola oil, and cotton seed oil are relatively inexpensive crops, and they show up in nearly every processed or prepared food marketed here. The only way to truly avoid these GM products is to eat strictly organic, as USDA organic standards currently prohibit the use of GMO products in “organic” products. back to top
3. Doull J, Gaylor D, Greim HA, Lovell DP, Lynch B, Munro IC (November 2007). "Report of an Expert Panel on the reanalysis by of a 90-day study conducted by Monsanto in support of the safety of a genetically modified corn variety (MON 863)". Food Chem. Toxicol.45 (11): 2073–85.
4. Finamore, A., Roselli, M., Britti, S., Monastra, G., Ambra, R., Turrini, A., and Mengheri, E. Intestinal and Peripheral Immune Response to MON810 Maize Ingestion in Weaning and Old Mice. J. Agric. Food Chem., 2008, 56 (23):11533–11539.
5. Gasnier C, Dumont C, Benachour N, Clair E, Chagnon MC, Séralini GE. Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines. Toxicology. 2009 August 21;262(3):184-91.
6. Hammond BG, Dudek R, Lemen JK, Nemeth MA (July 2006). Results of a 90-day safety assurance study with rats fed grain from corn borer-protected corn. Food Chem.Toxicol.44 (7): 1092–9.
7. Hammond B, Dudek R, Lemen J, Nemeth M (June 2004). Results of a 13 week safety assurance study with rats fed grain from glyphosate tolerant corn. Food Chem. Toxicol.42 (6): 1003–14.
8. Hammond B, Lemen J, Dudek R, et al. (February 2006). Results of a 90-day safety assurance study with rats fed grain from corn rootworm-protected corn. Food Chem. Toxicol.44 (2): 147–60.
9. Spiroux de Vendômois, et al. A Comparison of the Effects of Three GM Corn Varieties on Mammalian Health. Int J Biol Sci 2009; 5:706-726
10. Zentek, J. Fewer litters, fewer and smaller offspring, no offspring. Veterinary University of Vienna, Institute for Nutrition, Secretary +43 1 25077-3201, Prof. Dr. Jürgen Zentek: -3000 Email Juergen.Zentek@vu-wien.ac.at. Paper has been presented, but study not yet published.
And, now that I've tried to present the "unbiased" data, how do I REALLY feel about GMO food? Check out this cartoon video of Larry Leptin: