GM food has become more common, however, the controversies related to it is still important and still debating.
1. Controversies

1.1 Health issue
There are some effects on health of gm food. They are the allergens in gm food which causes allergies and transfer of antibiotic resistance markers to human body. Though genetic modification provides a chance to reduce or even eliminate the protein allergens that were found naturally in food. Though gm products have its own advantage, it may also add allergens to the food.
One such example is the Brazil nut allergens. A methionine-producing gene from Brazil nut is introduced into soybean to improve its nutrient content. Before these soybean was markets, test on allergens were carried out. It was found that the consumption of transgenic soybean could cause allergenic results in some individuals. This incident has increased the awareness about the possible risks associated with genetic modification food.

1.2 Environmental issue
Some very important and common impacts on the environment are "unintended tranfer of transgenes through cross-pollination, unknown effects on soil microbes, loss of flora and fauna biodiversity".
One example of unintended transfer of genes through cross-pollination. Monarch are the butterflies that feed on milkweed. However, when milkweeds are planted beside Bt maize, the milkweeds were covered with pollen. Monarch butterfly larvaes feed on these milkweeds and died. The death of these Monarch butterfly larvaes is due to the toxin that is transferred from the Bt maize to the milkweeds.

1.3 Ethical issue
GM food includes the combination of genes from different organisms or the transfer of genes from one source such as animals to food. Many is still debating about the issue of violating nature. Other than this, many concerns are "violation of natural organisms' intrinsic values, objections to consuming animal genes in plants and the stress caused on animals".

Reference
1. Genetically Modified Foods and Organisms. Human Genome Project Information. http://www.ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml; accessed on 7th June 2008
2. Genetically modified organisms, consumers, food safety and the environment. FAO Ethics Series. ftp://ftp.fao.org/docrep/fao/003/X9602e/X9602e00.pdf; accessed on 9th July 2008