Figure 5-2, from the EFSA report, shows the relationship between the number of experimental units (cages with two animals) per treatment group and the power of an experiment in standard-deviation units. Standard deviations quantify how much the measurement of a trait or effect varies among animals that have been given the same diet. The report concluded that, if researchers follow OECD Test No. 408 of 10 males and 10 females per treatment (OECD, 1998a), a test should be able to detect a difference equal to about 1 standard deviation (with 90-percent confidence) unless the food has a different effect on males and females, in which case, the smallest difference that could be detected would be about 1.5 standard deviations from the experimental mean.
Other research suggests that selenium, taken alone or with other nutrients, does not reduce the risk of death. Ovarian cancer. Research suggests that there is no link between selenium consumption in the diet and the risk for ovarian cancer. Mercury poisoning.
Consumers who regularly buy organic food are also more physically active and less likely to smoke [18, 19, 37]. Depending on the outcome of interest, associations between organic vs conventional food consumption and health outcome therefore need to be carefully adjusted for differences in dietary quality and lifestyle factors, and the likely presence of residual confounding needs to be considered. In children, several studies have reported a lower prevalence of allergy and/or atopic disease in families with a lifestyle comprising the preference of organic food [38,39,40,41,42,43,44]. However, organic food consumption is part of a broader lifestyle in most of these studies and associated with other lifestyle factors. Thus, in the Koala birth cohort of 2700 mothers and babies from the Netherlands , exclusive consumption of organic dairy products during pregnancy and during infancy was associated with a 36% reduction in the risk of eczema at age 2 years.
Furthermore, there have been claims and counterclaims about the relative safety of GE crops and their associated technologies compared with conventionally bred crops and their associated technologies. Therefore, the remainder of this chapter examines possible risks and benefits associated with GE crops and assesses the methods used to test them in and beyond government regulatory systems. Unintended effects of the targeted genetic changes on other characteristics of the food (for example, the intended presence of or increase in one compound in plant cells could result in changes in plant metabolism that affect the abundance of other compounds).
Many of the published criticisms of the SÃ©ralini et al. (2012, 2014) study commented on the small number of animals used in the study and on the strain of rats used. Examination of other whole-food GE crop studies indicates that the numbers of rats and the strain used were typical (Bartholomaeus et al., 2013). Indeed, OECD Test No. 408 for 90-day trials (OECD, 1998a) calls for 10 males and 10 females for each treatment. The criticism of SÃ©ralini et al. (2014) is that their analysis included the incidence of tumors, which would require more animals for a robust analysis (EFSA, 2012).
On the basis of data collected in the 2009-2010 National Health and Nutrition Examination Survey, Rubio-Tapia et al. (2012) reported a prevalence of celiac disease of 0.71 percent with 1.01 percent in non-Hispanic whites in a sample of 7,798 subjects. It should be noted that there has not been any commercial production of GE wheat, rye, or barley in the world.
It is possible to detect DNA, but the amounts are typically diminished in purified oils to 1 percent or less of the original content. Similarly, Oguchi et al. (2009) were not able to find any DNA in purified beet sugar.
Crab, liver, fish, poultry, and wheat are generally good selenium sources. The amount of selenium in soils varies a lot around the world, which means that the foods grown in these soils also have differing selenium levels. In the U.S., the Eastern Coastal Plain and the Pacific Northwest have the lowest selenium levels.
Food of the future: what will feed 7 billion people?
Another issue is that many statistical tests were performed in most studies. That could result in accumulation of false-positive results (Panchin and Tuzhikov, 2016). Although this is not a situation in which a stringent correction for doing multiple tests is called for (Dunn, 1961), there is reason to be cautious in interpretation of statistical significance of individual results because multiple tests can lead to artifactual positive results. The issue of multiple test results is common in many fields, and one approach used in genetics is to use the initial tests for hypothesis generation with follow-up experiments that test an a priori hypothesis (for example, Belknap et al., 1996). If a straightforward application of Bonferonni correction is used, each animal study that measures multiple outcomes, whether for GE crops or any other potential toxicant, could require over 1,000 animals to obtain reasonable statistical power (Dunn, 1961).
The discussion here focuses on how the methods have already been applied in the assessment of risk of health effects of currently commercialized GE crops. studies with much larger samples be conducted to determine whether there is reason to use 2-year studies generally, but the committee disagrees that this one study should lead to a general change in global procedures regarding the health effects and safety of GE crops.
In the future, the scale of genetic-engineering alterations may go much further than just manipulating oil profiles. The committee heard from speakers about projects aimed at changing the entire photosynthetic pathway of the rice plant (Weber, 2014) to create an entirely novel crop (Zhu et al., 2010; Ruan et al., 2012). The committee also heard from researchers interested in developing cereal crops with nitrogen fixation. Those projects are discussed further in Chapter 8.
Chapter: 5 Human Health Effects of Genetically Engineered Crops
Before promulgation of the GLP guidelines, study designs varied, so reproducibility and quality assurance of many studies were difficult to ascertain. In addition, the GLP guidelines set forth regulations for establishing the levels of compounds to be tested in the animal diet or in the dosage forms used in a study.
To raise the content to a point where it could alleviate vitamin A deficiency without consumption of very large amounts of rice, a second version of Golden Rice was produced by transforming the plant with the psy gene from maize. The carotene content was thereby raised above 30 Âµg/g (Paine et al., 2005). Varieties that yield well, have good taste and cooking qualities, and cause no adverse health effects from unintended changes in the rice could have highly important health effects (Demont and Stein, 2013; Birol et al., 2015). There have been claims that Golden Rice was ready for public release for well over a decade (Hefferon, 2015), but this is not the case.
A more complex example would be engineering of fish oils (very long-chain unsaturated fatty acids) to improve the health profile of plant oils; depending on the target species, this process has required introduction of at least of three and at most nine transgenes (Abbadi et al., 2004; Wu et al., 2005; Ruiz-Lopez et al., 2014). If each of those transgenes is integrated into the genome on a different chromosome on the basis of separate insertion events, it will require a number of generations of crosses to put them all together in one plant. If, instead, all the transgenes could be targeted at the same site on a chromosome either simultaneously or one after another, they would not segregate from each other as they were moved into elite varieties. From a food-safety perspective, engineering transgenes into a single target locus also ensures that expression of the whole pathway is preserved so that the correct end product accumulates.
Plant breeders have generally screened for toxins that are typical of the plant group from which a crop was domesticated and have excluded plants that have high concentrations of the compounds. In this chapter, the committee examines the evidence that substantiates or negates specific hypotheses and claims about the health risks and benefits associated with foods derived from genetically engineered (GE) crops.