Indeed, much of the vegetarian popular press seems to be written by authors who glom onto any statement, of whatever quality, that has positive implications for vegetarianism, without even trying to understand the full body of evidence in the field, evidence that frequently suggests they are wrong. But recall that no single study is worth very much. It might be impressive to see three studies linking dietary fat and cancer in a footnote, until you realize that there are thousands of studies that address this relationship. You can hunt down three of them that say anything. Even if the author reported one hundred such studies in the footnotes, you could not be sure there were not five hundred others that said just the opposite.
Health research is a rather inexact business, and good studies can produce different results.
Ultimately, the reader is really relying on the author's implicit assertion that he or she understood the full weight of evidence on a topic and represented it accurately. Who To Believe Ultimately, there are two paths to determining what to believe, and the first of them is seldom possible. The first path is knowing enough technical details about a topic or a method of inquiry to be able to judge it directly. But none of us can have the required level of expertise in more than a few areas. This leaves only the second path, figuring out who to believe.