Genetically modified foods are relatively new to the food supply, and people have only been consuming these foods since the mid-1990s when the first genetically modified tomatoes appeared in grocery stores. There is no long-term data on how genetically modified foods affect human health. Clinical trials done on animals that were fed genetically modified crops are of short duration and show mixed outcomes. A study published in the "International Journal of Biological Sciences" in December 2009, notes that rats fed genetically modified corn had a decline in liver, kidney, heart, adrenal gland and spleen health and function. Short-term studies in which animals were fed genetically modified foods for only 4 weeks usually show few negative side effects. No research has been conducted on the health and safety for people who eat genetically modified foods.