This study investigates the relationship among (1) college major, (2) knowledge used in reasoning about common health beliefs, and (3) judgment about the accuracy of those beliefs. Seventy-four college students, advanced biology and non-science majors, indicated their agreement or disagreement with commonly believed, but often inaccurate, statements about health and explained their reasoning. The results indicated that while the direct impact of college-level biology coursework on judgment accuracy was minimal, biology major was associated with increased reliance on advanced biological reasoning, which mediated judgment accuracy. However, the overall association of advanced biological reasoning with judgment accuracy was small. The discussion calls for strengthening the science--daily life connection in biology education for majors and nonmajors.