 Key elements of the assessment procedure are the molecular , compositional , phenotypic and agronomic analysis in order to identify similarities and differences between the GM plant and its near isogenic counterpart . The safety assessment is focussed on ( i ) the presence and characteristics of newly expressed proteins and other new constituents and possible changes in the level of natural constituents beyond normal variation , and on the characteristics of the GM food and feed , and ( ii ) the possible occurrence of unintended ( unexpected ) effects in GM plants due to genetic modification . In order to identify these effects a comparative phenotypic and molecular analysis of the GM plant and its near isogenic counterpart is carried out , in parallel with a targeted analysis of single specific compounds , which represent important metabolic pathways in the plant like macro and micro nutrients , known anti-nutrients and toxins . Significant differences may be indicative of the occurrence of unintended effects , which require further investigation . Section 0 provides an overview of studies performed for the safety and nutritional assessment of whole food and feed . Extensive experience has been built up in recent decades from the safety and nutritional testing in animals of irradiated foods , novel foods and fruit and vegetables . These approaches are also relevant for the safety and nutritional testing of whole GM food and feed . Many feeding trials have been reported in which GM foods like maize , potatoes , rice , soybeans and tomatoes have been fed to rats or mice for prolonged periods , and parameters such as body weight , feed consumption , blood chemistry , organ weights , histopathology etc have been measured . The food and feed under investigation were derived from GM plants with improved agronomic characteristics like herbicide tolerance and/or insect resistance . The majority of these experiments did not indicate clinical effects or histopathological abnormalities in organs or it issues of exposed animals . In some cases adverse effects were noted , which were difficult to interpret due to shortcomings in the studies . Many studies have also been carried out with feed derived from GM plants with agronomic input traits in target animal species to assess the nutritive value of the feed and their performance potential Studies in sheep , pigs , broilers , lactating dairy cows , and fish , comparing the in vivo bioavailability of nutrients from a range of GM plants with their near isogenic counterpart and commercial varieties , showed that they were comparable with those for near isogenic non-GM lines and commercial varieties . In Section 0 toxicological in vivo , in silico , and in vitro test methods are discussed which may be applied for the safety and nutritional assessment of specific compounds present in food and feed or of whole food and feed derived from GM plants . Moreover the purpose , potential and limitations of the 00-day rodent feeding trial for the safety and nutritional testing of whole food and feed have been examined . Methods for single and repeated dose toxicity testing , reproductive and developmental toxicity testing and immunotoxicity testing , as described in OECD guideline tests for single well-defined chemicals are discussed and considered to be adequate for the safety testing of single substances including new products in GM food and feed . Various in silico and in vitro methods may contribute to the safety assessment of GM plant derived food and feed and components thereof , like ( i ) in silico searches for sequence homology and/or structural similarity of novel proteins or their degradation products to known toxic or allergenic proteins , ( ii ) simulated gastric and intestinal fluids in order to study the digestive stability of newly expressed proteins and in vitro systems for analysis of the stability of the novel protein under heat or other processing conditions , and ( iii ) in vitro genotoxicity test methods that screen for point mutations , chromosomal aberrations and DNA damage/repair . The current performance of the safety assessment of whole foods is mainly based on the protocols for low-molecular-weight chemicals such as pharmaceuticals , industrial chemicals , pesticides , food additives and contaminants . However without adaptation , these protocols have limitations for testing of whole food and feed . This primarily results from the fact that defined single substances can be dosed to laboratory animals at very large multiples of the expected human exposure , thus giving a large margin of safety . 