Do Genetically Engineered Foods Have Changes in Nutritional Content?Response:
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).
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19. Monsanto. 2008. About Vistive. https://www.vistive.com/about-vistive/Pages/about-vistive.aspx. Last accessed 2011-11-25. PDF