Do Genetically Engineered Foods Have Changes in Nutritional Content?

Preventing adverse health effects of foods requires the application of appropriate scientific methods to predict and identify unintended compositional changes resulting from genetic modification of plants, animals, and microbes  —whether by classical or rDNA methods. It is the final product, rather than the means by which it is modified, that is more likely to result in unintended effects (1). Nonetheless, the nutritional composition of GE foods, including levels of protein, carbohydrate, fat, vitamin, mineral, fiber, moisture, and phytochemicals, is analyzed for substantial equivalence, and levels of individual nutrients and antinutrients in GE foods are compared with levels in conventional counterparts (see “Are Food Safety Studies Conducted on GE Foods?”).

When considering substantial equivalence, it is important to note that a range of natural variation is observed in conventionally bred cultivars when grown under similar conditions (2). Therefore, comparisons of nutritional content of GE foods must be measured against variation in conventional foods grown under comparable conditions. For example, nutrient composition of GE potato tubers was compared with control wild-type and tissue culture–derived non-GE potato tubers of two cultivars, cv. Record and cv. Desiree, grown under the same conditions. Data were analyzed using targeted compositional analyses (3). An analysis of variance (ANOVA) for the major consensus nutrient compounds, recommended by the Organization of Economic Cooperation and Development (4) as being appropriate for safety assessment of novel foods, was conducted and no consistent differences, outside normal variation, were found among the tubers.

Extensive nutritional equivalence studies of Roundup Ready® soybeans have been conducted. These studies include analyses of protein, oil, fiber, carbohydrate, ash, and moisture content and the amino acid and fatty acid composition in both seeds and toasted soybean meal; the values were compared with those from conventional soybeans. Special attention was given to levels of antinutrients and phytonutrients typical for soybeans, e.g., trypsin inhibitors, lectins, and isoflavones (5). One significant difference was detected in defatted, nontoasted soybean meal, the starting material for the production of commercially utilized soybean protein. The variation was in trypsin inhibitor levels, which were 11%–26% higher in GE soybeans than in wild-type. However, levels in seeds and defatted, toasted soybean meal, the form used in foods, were similar for all lines. The results demonstrated that the composition of these GE lines is equivalent to that of conventional soybean cultivars in the form consumed by humans. Equivalence of the feeding value of this GE soy was also demonstrated by feeding it to rats, chicken, catfish, and dairy cattle (6). A broader study using Bt corn and Roundup Ready® corn and soybean to look at composition, digestibility, and feeding value for sheep, chickens, and beef and dairy cattle concluded that seeds of the GE varieties were substantially equivalent to seeds from isolines of non-GE varieties (7).

A 1999 study of nutritional equivalence by Lappé and others (8), often cited by those concerned about GE crops, showed that Roundup Ready® soybeans had reduced levels of isoflavones, notably genistin and daidzin, and thus had significant implications for human health given the potential positive health benefits of the two compounds. The American Soybean Association published a response to this study indicating the variation in phytoestrogen levels was within the limits of variability for conventional soybean varieties (1). In fact, not all comparisons in the Lappé study of the two compounds in conventional versus transgenic varieties showed reduced levels; some showed significant increases (9, table 1). Another phytoestrogen, glycitin, showed significant decreases in only two of seven samples. These results underscore the variability of phytoestrogen levels from sample to sample. A premise of the Lappé study (9) was that other studies on Roundup Ready® soybean used seeds from non-herbicide-treated plants and this raised concerns on the basis of preliminary data from Phaseolus that herbicide treatment might generate increased levels of phytoestrogens (10). However, the original 1999 study on Roundup Ready® soybean safety was performed on seed from herbicide-treated plants and no differences in phytoestrogen levels were observed (11).

It is important to note that genetic engineering can purposefully be used to change the nutritional profiles of foods. In these cases studies similar to those described above would be conducted; the mandate for substantial equivalence would apply only to compounds unrelated to the introduced trait. Examples of such foods include those with increased β-carotene (12, 13), flavinoids (14, 15), calcium (16), folate (17), and iron availability (18) (See section 2.9). According to FDA policy, GE foods with altered nutritional traits must be labeled to indicate nutritional differences; one example is VistiveTM, a low-linoleic oil from GE soybeans that can be used instead of trans fat–containing oils (19).

References:

1. Comm. Identifying Assessing Unintended Effects Genet. Eng. Foods Human Health. 2004. Safety of Genetically Engineered Foods: Approaches to Assessing Unintended Health Effects. Washington, DC: Natl. Acad.

2. Shewry PR, Baudo M, Lovegrove A, Powers S, Napiera JA, et al. 2006. Are GM and conventionally bred cereals really different? Trends Food Sci. Technol. 18:201–9

3. Shepherd LVT, McNicol JW, Razzo R, Taylor MA, Davies HV. 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 of substantial equivalence of key nutrients and antinutrients in genetically engineered potatoes.

4. Org. Econ. Coop. Dev. 2007. Consensus document on compositional considerations for new varieties of potatoes: Key food and feed nutrients, anti-nutrients and toxicants. http://www.oecd.org/dataoecd/15/62/46815167.pdf. Last accessed 2011-11-25. PDF

5. Padgette SR, Taylor NB, Nida DL, Bailey MR, MacDonald J, et al. 1996. The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans. J. Nutr. 126:702–16
First peer-reviewed report on equivalence of genetically engineered and conventional soybean.

6. Hammond BG,Vicini JL, Hartnell GF, Naylor MW, Knight CD, et al. 1996. The feeding value of soybeans fed to rats, chickens, catfish and dairy cattle is not altered by genetic incorporation of glyphosate tolerance. J. Nutr. 126:717–27

7. Clark JH, Ipharraguerre IR. 2001. Livestock performance: Feeding Biotech Crops. J. Dairy Sci. 84:E9–18

8. Lappé MA, Bailey EB, Childress C, Setchell KDR. 1999. Alterations in clinically important phytoestrogens in genetically modified, herbicide tolerant soybeans. J. Med. Food 1:241–45

9. Koprek T, McElroy D, Louwerse J,Williams-Carrier R, Lemaux PG. 2000. An efficient method for dispersing Ds elements in the barley genome as a tool for determining gene function. Plant J. 24:253–63

10. Sandermann H,Wellmann E. 1998. Risikobewertung der kunstlichen herbizidresistenz. Biol. Sicherheit 1:285–92

11. Taylor NB, Fuchs RL, MacDonald J, Shariff AR, Padgette SR. 1999. Compositional analysis of glyphosate-tolerant soybeans treated with glyphosate. J. Agric. Food Chem. 47:4469–73

12. Paine JA, Shipton CA, Chaggar S, Howells RM,Kennedy MJ, et al. 2005. Improving the nutritional value of Golden Rice through increased provitamin A content. Nat. Biotechnol. 23:429–30
Seminal paper describing secondgeneration, nutritionally enhanced Golden Rice.

13. Ye X, Al-Babili S, Kloti A, Zhang J, Lucca P, et al. 2000. Engineering the provitamin A (β-carotene) biosynthetic pathway into (carotenoid-free) rice endosperm. Science 287:303–5

14. Deavours BE, Dixon RA. 2005. Metabolic engineering of isoflavonoid biosynthesis in alfalfa. Plant Physiol. 138:2245–59

15. Rein D, Schijlen E, Kooistra T, Herbers K, Verschuren L, et al. 2006. Transgenic flavonoid tomato intake reduces C-reactive protein in human C-reactive protein transgenic mice more than wild-type tomato. J. Nutr. 136:2331–37

16. Park S, Kang T-S, Kim C-K, Han J-S, Kim S, et al. 2005. Genetic manipulation for enhancing calcium content in potato tuber. J. Agric. Food Chem. 53:5598–603

17. Diaz de la Garza RI, Gregory JF III, Hanson AD. 2007. Folate biofortification of tomato fruit. Proc. Natl. Acad. Sci. USA 104:4218–22

18. Drakakaki G, Marcel S, Glahn RP, Lund EK, Pariagh S, et al. 2005. Endosperm-specific coexpression of recombinant soybean ferritin and Aspergillus phytase in maize results in significant increases in the levels of bioavailable iron. Plant Mol. Biol. 59:869–80

19. Monsanto. 2008. About Vistive. https://www.vistive.com/about-vistive/Pages/about-vistive.aspx. Last accessed 2011-11-25. PDF

Updated 2/16/12