Why are biotech crops not labeled in the United States?

Many people ask why these biotech foods are not labeled by FDA if they contain a new protein that is intentionally added to food (e.g., the Bt protein in corn) or if the food was produced from crops produced using biotechnology. Food additives are defined by FDA as substances intentionally added to foods that are significantly different in structure, function, or amount than current food substances. Also, FDA requires labeling of food only when there is modified nutritional profile or digestibility of food, changes in composition or creation of a new entity, or introduction of a natural plant toxin or non-GRAS food additive. In the case of Bt corn, a new protein was added to corn, but the corn and food derived from it did not require labeling because there was no change in nutritional profile or composition.