In Larry McMurtry's book "Cadillac Jack," the narrator expresses a contrarian view on nutrition, stating a disbelief in the concept of protein, likening it to a myth. This skepticism extends to vitamins and nutrition as a whole, suggesting a deep cynicism about commonly accepted health beliefs.

This view reflects a broader theme of questioning societal norms and the ideas that people often take for granted. The statement provokes thought about the nature of nutrition and how it's perceived, indicating a rejection of conventional wisdom in favor of a more critical, possibly nihilistic perspective.