© 2022 Wiley Periodicals LLC.Numerosity effects have been investigated in the psychology and marketing literatures. While the effects are documented in outcomes including money and temperature judgments, the potential application and effects of numerosity for nutrition labeling remain unexplored. In this work, we propose that vigilance offers one circumstance when individuals might succumb to numerosity effects. Within the context of nutrition labeling, we propose that the increased vigilance that people with diet-sensitive illnesses have for specific nutrients on nutrition labels, counter-intuitively, exacerbates the numerosity effect. We demonstrate that those with diabetes and those with hypertension, for example, are more vigilant for information on nutrition labels relevant to their condition, sugar, and salt, and this greater vigilance counterintuitively leads them to exhibit greater numerosity effects for those nutrients, influencing their food perceptions. As an illustration, we find that a person with hypertension would consider a food product with, say, 3 g of sodium to have less sodium content and be more healthful than one with 3000 mg, although the quantities are equivalent. Our research highlights to policymakers that a “one-size-fits-all” solution for nutrition labeling is not appropriate.