Genetic engineering is being applied to eliminate or substantially reduce plant-derived substances that can be harmful to human health in otherwise nutritious foods. Post-transcriptional gene silencing, most recently via RNA interference, has been used in efforts to remove allergens from rice, soybean, apple, tomato, and peanut. RNA silencing has the potential to simultaneously alter expression of all members of a multi-gene family in a tissue-specific manner with little collateral change in the plant. Similarly, RNA silencing, as well as the overexpression of a beneficial gene, have been used in transgenic cassava to reduce toxic cyanogens. These studies are illustrative of the future application of biotechnology toward production of foods that are of direct value to the consumer.