2.10—Chemical Composition of crops is highly variable

Food and feed crops exhibit a range of chemical compositions

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

The discussion of chemical composition in Genetic Roulette is both uninformed and misleading. Smith fails to realize that crop composition varies by variety, growing season, geographical location, and even location within a farmer’s field. GM crops approved and planted around the world have been shown to have compositions that are not meaningfully different than other varieties of the same crop—all varieties show small differences from one another. No harm or health effect has ever been associated with the small changes in composition that are commonly encountered. Moreover, since GM crops are carefully analyzed it can be said that they are more likely to be nearly identical in composition to other varieties than are new conventional varieties that are not regulated or tested. Smith proves his ignorance of the topic by citing a long discredited paper that claims GM soybeans have 14% less isoflavones than other soybeans. Smith is unaware that soybean isoflavone content varies by 200-300% but that GM soybeans have been shown to have the same isoflavone content as their parental strain.

1. Plants don’t have a single fixed composition but vary greatly in composition depending on variety, place of planting, and year of cultivation. The plants that we use as food and feed contain a wide variety of plant-produced chemicals such as anthocyanins, glucosinolates, isoflavones, terpenoids, and phenolic compounds (Ames and others 1990, Baxter and Borevitz 2006, Hartmann 2007, Morant and others 2008). Among different foods and different conventional varieties of food crop there is considerable variability in the amounts of these chemicals (Catchpole and others 2005, Ioset and others 2007, Sautter & Urbaniak 2007, Wang and Murphy 1994). Genetic Roulette makes no mention of this fact.

2. Commercial GM crops have the same composition as other varieties of the same crop. There have been many studies on GM crops that show that they contain only small variations in chemical composition (Catchpole and others 2000, Cellini and others 2004, Ioset and others 2007, Lemaux P 2008. Section 3.6. Do genetically engineered foods have changes in nutritional content?, Padgette and others 1996, Shepherd and others 2006, Shewry and other 2006,Taylor and others 1999). The differences observed are well within the natural range of chemical content seen among conventional crop varieties of a given food or feed crop. Put another way, the composition of conventional varieties of a crop differ from one another more than a GM crop differs from its conventional parent—GM technology actually produces fewer and smaller changes.

3. It is particularly important to understand that crop foods are biological materials and as such, they display biological variability. Chemical composition is important for understanding safety tests (Cellini and others 2004, EFSA GMO Panel Working Group on Animal Feeding Trials 2008). For any animal feeding test with soybeans for instance, the content of isoflavone-type chemicals present in a soybean has to be accurately determined. Such information is needed to ensure that any changes in growth of animals are not caused by changes in the isoflavone content among different soy meals being compared for effect on animals (Brown and Setchell 2001, Thigpen and others 2004).

4. Any discussion of changes in composition must take into account that crops exhibit a range of content for each constituent—no GM crop has ever been approved that has a biologically significant difference in any component. Genetic Roulette’s discussion of changes in chemical content caused by genetic engineering without any appreciation of the common occurrence of such changes in conventional foods and their influence on nutrition is not an instructive or useful analysis of food safety.

5. Smith’s discussion of “lower” isoflavone content of GM soybeans is a perfect example of a biased and flawed analysis. Smith cites a paper that claims Roundup Ready soybeans have a 12-14% lower isoflavone content than conventional soybeans. The problem is the study is poorly designed and does not take into account other papers that show the results they claim are essentially meaningless (Padgette SR and others 1996, Taylor NB and others 1999, (Petterson and Kiessling 1984, Wang and Murphy 1994). For example, the study uses a GM soybean and a control soybean that are different varieties—they do not grow their soybeans, they buy them. Prior publications report that soybean varieties vary by as much as 200-300% in isoflavone content, and that the same variety grown in different locations can vary by 200-300% in isoflavone content (Petterson and Kiessling 1984, Wang and Murphy 1994). Not only is a 14% difference meaningless, Smith ignores two peer-reviewed publications that report that Roundup Ready soybeans have the same content of isoflavones as other soybeans (Padgette and others 1996, Taylor and others 1999).

Genetic Roulette demonstrates that it has no intention of telling the reader what the scientific literature (Lemaux 2008, Section 3.6.) really says. The anti-GM activists still cite the paper Smith cites as an indication of GM soy having decreased isoflavones.


Ames BN and others (1990). Dietary pesticides 99.99% all natural. Proceedings of the National Academy of Sciences U.S.A. 87: 7777–7781. Most pesticides in our diet are made by the plants themselves.

Baxter I R & Borevitz J O (2006). Mapping a plant’s chemical vocabulary Nature Genetics 38(7):737-738. Wild varieties of mustard illustrate the huge diversity and variability of chemicals in plants.

Brown NM and Setchell KDR (2001). Animal models impacted by phytoestrogens in commercial chow: implications for pathways influenced by hormones. Laboratory Investigation 81:735–747. “All investigators should be vigilant to the phytoestrogen composition of commercial rodent diets because there is a history of potent biological effects in larger animals and humans from high circulating isoflavone concentrations.

Catchpole GS and others (2005). Hierarchical metabolomics demonstrates substantial compositional similarity between genetically modified and conventional potato crops. PNAS October 4, 2005 vol. 102 no. 40 14458-14462

Cellini F and others (2004). Unintended effects and their detection in genetically modified crops. Food and Chemical Toxicology 42:1089-1125. Unintended effects are those outcomes that are totally unexpected and not predictable. This paper focuses on technology for detection of such unexpected outcomes, and this includes metabolomics, proteomics, and transcriptomics. These buzzwords correspond to various forms of chemical fingerprinting.

EFSA GMO Panel Working Group on Animal Feeding Trials. (2008). Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials. Food Chemistry and Toxicology 46 Suppl 1:S2-70. Epub 2008 Feb 13. Review. Comprehensive and authoritative review of the state of play with animal feeding trials carried out with genetically modified crops, including discussion of their strengths and weaknesses. Experts associated with the European Food Safety Authority provide a comprehensive listing of many animal feeding tests and in-depth technical analysis of their interpretation.

Hartmann T (2007). From waste products to ecochemicals: Fifty years research of plant secondary metabolism Phytochemistry 68 (2007) 2831–2846

Ioset JR and others (2007). Flavonoid profiling among wild type and related GM wheat varieties. Plant Molecular Biology 65 (5), 645-654

Lemaux P (2008). Section 3.6. Do genetically engineered foods have changes in nutritional content? In Review: Genetically engineered plants and foods: a scientist’s analysis of the issues (Part I). Annual Review Plant Biology 59:771–812. Discusses the need to assess normal range of variation in plant composition when deciding whether genetic engineering causes changes. Provides key references to studies on comparative composition.

Morant A V and others (2008). Beta-glucosidases as detonators of plant chemical defense. Phytochemistry 69:1795–1813

Padgette SR and others (1996). The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans. J. Nutr. 126:702–16

Petterson H and Kiessling KH (1984). Liquid chromatographic determination of the plant estrogens coumesterol and isoflavones in animal feed. Journal of the Association of Official Analytical Chemists 67:503-506

Sautter C & Urbaniak B (2007). Flavanoids for environmental equivalence profiling of GE plants ISB News Report. December 2007.

www.isb.vt.edu/news/2007/artspdf/dec0703.pdf pdf file accessed Dec 21 2008

Shepherd LVT and others (2006). Assessing potential for unintended effects in genetically modified potatoes perturbed in metabolic and developmental processes. Targeted analysis of key nutrients and antinutrients. Transgenic Res. 15:409–25. Demonstration that key nutrients and antinutrients in genetically engineered potatoes are substantially equivalent.

Shewry PR and other (2006). Are GM and conventionally bred cereals really different? Trends Food Sci. Technol. 18:201–9

Taylor NB and others (1999). Compositional analysis of glyphosate-tolerant soybeans treated with glyphosate Journal of Agricultural and Food Chemistry 47 (10):4469-4473. DOI: 10.1021/jf990056g. Other studies had shown that GM and non-GM soybeans compositionally equivalent. This study shows that glyphosate treated soybeans are compositionally equivalent to non-treated soybeans.

Thigpen JE and others (2004). Selecting the appropriate rodent diet for endocrine disruptor research and testing studies. ILAR Journal. 45:401-416. Rodent diets differ significantly in estrogen activity primarily due to large variations in phytoestrogen content. These estrogens can profoundly influence rodent physiology.

Wang H-J and Murphy PA (1994). Isoflavone composition of American and Japanese soybeans in Iowa: Effects of variety, Crop year, and location J. Agric. Food Chem. 42:1674-1677. Total isoflavone content varies over a 400% range.

Genetic Roulette Falsely Claims:

Changes in proteins can alter thousands of natural chemicals in plants, increasing toxins or reducing phytonutrients

  1. Plants produce thousands of chemicals which, if ingested, may fight disease, influence behaviour will be toxic.
  2. The genome changes described in this section [ of the book Genetic Roulette ] can alter the composition and concentration of these chemicals.
  3. GM soybeans, for example, produce less cancer-fighting isoflavones.
  4. Most GM-induced changes in these natural products go undetected.

Smith notes that plants contain thousands of natural chemicals and speculates that changes in the levels of any of these chemicals may cause harm.