Every month, around two billion people see AI Overviews, Google’s AI-powered search feature that generates summaries to users’ queries. Now, a new study is revealing a concerning pattern among some of these responses: When asked health-related questions, AI Overviews appears to turn to YouTube significantly more often than trusted medical sites.
Since its inception, AI Overviews has faced its fair share of controversies, from early reports of the product spewing nonsensical answers to a series of lawsuits from businesses and publisher groups alleging that the feature is damaging to organic traffic patterns. The most recent concern with AI Overviews emerged via an investigation from The Guardian on January 2, which alleged that the tool has a tendency to provide users with false, misleading, and potentially dangerous health guidance. At the time, Google refuted those claims.
Now, a new study from the AI SEO tool SE Ranking, published on January 14, has revealed that AI Overviews is two to three times more likely to cite YouTube videos than “trusted medical sites” in response to health queries—but Google says that’s not the full picture.
“From the AI’s point of view, all of this content exists in the same pool.”
To understand how AI Overviews collects its health guidance on the web, researchers at SE Ranking analyzed more than 50,000 health-related Google searches from German users. That location was chosen, per the study’s authors, for its strictly regulated healthcare system.
“If AI systems rely heavily on non-medical or non-authoritative sources even in such an environment,” the authors wrote in a published report, “it suggests the issue may extend beyond any single country.”
SE Ranking found that, of all the AI Overview results, only about 34% came from “trusted medical sources” (which it defines as sites like medical institutions, academic journals, government institutions, and more), while the other 66% originated from “general or non-expert sources” (like commercial sites or blogs).
In fact, YouTube was the leading source for all health-related inquiries; accounting for 4.43% of all AI Overviews citations. According to the report, that’s 3.5 times more citations than netdoktor.de, one of Germany’s largest consumer health portals, and more than twice the citations of MSD Manuals, a well-established medical reference. In total, 20,621 out of 465,823 AI Overviews results cited YouTube.
“This matters because YouTube is not a medical publisher,” the report reads. “It is a general-purpose video platform. Anyone can upload content there (e.g., board-certified physicians, hospital channels, but also wellness influencers, life coaches, and creators with no medical training at all). From the AI’s point of view, all of this content exists in the same pool.”
In a statement to Fast Company, Google refuted SE Ranking’s findings. The company said the study’s definition of a trustworthy source is “flawed and overly simplistic,” adding that, “it classifies nearly two-thirds of sources as ‘less reliable’ by lumping together everything from commercial sites to multi-topic blogs. This ignores the reality that an expert-written article on a “multi-topic blog” can be a high-quality source.”
Google noted that a close look at the report’s top 10 most-cited domains—which, alongside YouTube, include the German Heart Foundation and the country’s second-largest health insurer—reveals that they are “virtually all respected, authoritative sources for information, which directly contradicts the report’s central narrative.”
Further, it added, the claim that AI Overviews turns to YouTube two to three times more than trusted medical sites “ignores the fact that a wide variety of credible health authorities and licensed medical professionals create content on YouTube.” Google pointed to the fact that, per the study’s own findings, 24 of the 25 most-cited YouTube videos came from medical-related channels like hospitals, clinics, and health organizations. (Though, SE Ranking’s researchers note in the report, those 25 videos are “just a tiny slice” of all YouTube videos that AI Overviews actually links).
In all, a spokesperson said, “The implication that AI Overviews provide unreliable information is refuted by the report’s own data, which shows that the most-cited domains in AI Overviews are reputable websites. And from what we’ve seen in the published findings, AI Overviews cite expert YouTube content from hospitals and clinics.”