A non-human molecule found in red meat and milk makes its way into the human system when eaten -- and seems to build up especially in tumors, U.S. researchers reported on Monday. The compound, called sialic acid, is found on the surfaces of animal cells but is not found in people, and may be one reason why animal-to-human organ and tissue transplants do not work well. Animals have a version called Neu5Gc, while humans carry Neu5Ac. But researchers at the University of California San Diego found it does show up in the human body, and showed it can be absorbed from eating red meat and milk. Reuters