If you want to prove that eating fake meat has no additional adverse side effects to real meat, there would need to be studies. Have there been studies? No, there haven't. You can't assert that the two are the same because of a lack of evidence if there has been no attempt to find evidence. Until you have controlled experiments where people are exclusively fed both (preferably for at least a year, IMHO) you can't just conclude that 'well they seem the same so they must be'.