The health consequences of eating genetically modified organisms are largely unknown. Genetically engineered foods have not been shown to be safe to eat and may have unpredictable consequences. When trans-fats were first introduced, corporations battled to get them onto your grocery shelves - and it is only decades later that this once onvel food has been proven to be extremely unhealthful. Many scientists are worried that the genetically altered foods, once consumed, may pass on their mutant genes to bacterium in the digestive system, just like canola plants on the roadsides of North Dakota. How these new strains of bacteria may affect our body systems' balance is anybody's guess.
Genetic engineering reduces genetic diversity. When genes are more diverse, they are more robust; this is why a pure bred dog tends to have greater problems than the dear old mutt. Plants with reduced genetic diversity cannot handle drought, fungus invasions or insects nearly as well as natural plants, which could have dire consequences for farmers and communities dependent on GMO crops for survival.