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Genetically modified foods may differ, depending on the desirable traits they are designed to include. There have been three major movements involving genetically modified foods.

The first genetically modified foods focused on making plants easier and cheaper to produce. Desirable traits for these purposes include:

• Pest resistance. Many plants have been genetically altered to produce a chemical that is toxic to certain pests (e.g., insects, fungi) but harmless to humans. Crops that have been altered in this way include corn, soybeans, canola, apples and wheat.
  
  
• Herbicide tolerance. Plants have also been genetically altered to be able to better withstand herbicides. This allows farmers to kill weeds without harming the crop. Foods that have been modified in this way include soybeans, corn, sugar beets, alfalfa, canola, wheat, lettuce and rice.
  
  
• Disease resistance. Plants have also been genetically modified to resist certain diseases. Crops modified in this way include corn, bananas and papayas.
  
  
• Increased production. Some plants have been genetically altered to produce higher crop yields under specific environmental conditions.

Later, genetically modified foods focused on potential benefits to the consumer. Many of these foods may not be available or approved for human consumption. Desired traits for these purposes include:

• Enhanced health and nutritional value. Several different plants have been genetically modified to include additional nutrients. For example, rice has been developed with added beta-carotene, and soybeans that contain higher levels of protein are being developed. Genetic modification is also being used to reduce the amounts of saturated fats in cooking oils and to reduce the absorption of oil in potatoes. In addition, early results on the development of a reduced-allergen soybean appear promising.
  
  
• Improved appearance or taste. Genetic modification may make foods look better, taste better and stay fresh longer. This includes citrus fruits with less bitterness, tomatoes with more flavor, and other fruits and vegetables with improved shelf life.
  
  
• Increased adaptability to environmental conditions. Rice has been genetically modified to grow in harsh conditions, such as drought, cold temperatures or in salty soil. This type of modification may also be used for corn, wheat and other cereals.
  
  
• Other benefits. Genetical modification is being explored for other benefits to consumers (e.g., beans that cause less flatulence).

More recently, genetically modified foods are being designed to focus on pharmaceutical and environmental benefits. These foods are still in the developmental stage. Desirable traits for these purposes include:

• Potential pharmaceutical use. Genetically modified plants (e.g., fruits, vegetables) may be able to produce proteins that may function as edible medications or vaccines. Potential vaccines under development include those for measles, Hepatitis B, Norwalk virus, diarrhea and cholera. Medications that may be available in genetically modified foods include antibiotics, anticoagulants, blood substitutes and hormones.
  
  
• Potential environmental use. Genetically modified plants may be able to aid the environment in a number of ways. Plants may be modified to reduce the spread of mosquito-borne malaria. Plants may be modified to absorb certain toxic or hazardous substances in the soil or water. Genetic modification may also help protect nonfood plants (e.g., trees) from diseases.