Is genetically modified food safe to eat?

Some say they are safe, others say they are not safe, and others say the safety of GMOs is not known. Since long-term human or animal studies were not done before they were introduced into the food chain, the safety of GMO foods is not actually known. There is some evidence that the GMOs, the herbicides used on them, and/or the substance produced in certain genetically engineered crops does cause health issues in humans.