Pope John Paul II on Monday denounced as "morally contradictory" any medical treatment based on stem cells taken from embryo tissue.
In a speech to scientists Monday, the pope said research into stem cell technology "has understandably grown in importance in recent years because of the hope it offers for the cure of ills affecting many people."
John Paul suffers from Parkinson's Disease, one of the ailments that might benefit from stem cell research. However, he reiterated the Vatican position that "stem cells for purposes of experimentation or treatment cannot come from human embryo tissue."
"Any treatment which claims to save human lives, yet is based on human life in its embryonic state, is logically and morally contradictory, as is any production of human embryos for the direct or indirect purpose of experimentation or eventual destruction," the pope told participants in a meeting organized by the Pontifical Academy of the Sciences, an advisory body.
Research, instead, should be conducted on adult human tissue or "tissue superfluous to normal fetal development," the pontiff added.
Because stem cells can develop into any body tissue, scientists say they hope for one day being able to treat a variety of diseases from Parkinson's to diabetes to spinal cord injuries.