The advantages associated with genetically-modified foods start at the farm, where genetically-engineered seeds are more resistant to diseases that can decimate crops -- a particularly important factor in less developed countries completely dependent upon agriculture and vulnerable to diseases and insects that would otherwise destroy the fields. Once in the grocery store, genetically-modified food can provide higher levels of essential nutrients, and have longer shelf-lives. In addition, if the seeds are modified before planting to make them resistant to insects and diseases, they pesticides are less necessary, thereby causing less environmental contamination and posing less of a potential health hazard to the consumer.
Disadvantages to genetically-modified foods include the long-term health problems that may be associated with consumption of such foods. While the federal Food and Drug Administration must authorize the sale of genetically-modified foods in American stores, many people are concerned that the FDA certification process does not adequately factor in those long-term concerns. The growth of tumors in lab mice fed modified food, for example, has raised concerns among some scientists.
There are also concerns that genetically-modified crops adversely affect ecosystems, as insects like butterflys and bees that feed off of such crops are adversely affected in ways that reverberates throughout food chains.
The largest potential disadvantage to the use of genetically-modified foods, however, lies in the unknown. It may be decades before the full ramifications of the use of such foods is known.