Information diversity and authority shifts in Google’s AI overviews : an audit of health queries

Abstract

Commercial search engines are shifting from being intermediaries to generative answer engines, significantly altering Health Information-Seeking Behavior (HISB). Auditing these “black-box” systems is challenging due to dynamic client-side rendering and restricted data access. To address this, we use a custom-built browser extension to collect search engine results data. In a study of 900 health-related queries in Google US, we found an AI prevalence of 87.7% and a substantially low source overlap of 46.2% between organic results and AI citations. We observe a distinct platform shift: while organic rankings favor clinical authorities, generative AI elevates user-generated multimedia, making YouTube the second-most-cited source. Given high user trust in AI responses, this shift poses risks to public health, highlighting the need for independent auditing toolkits.