In a concerning revelation, research has found that Google’s AI-powered search feature, Google AI Overview, heavily relies on YouTube as a source for answering health-related queries, raising fresh questions about the reliability of a tool seen by 2 billion people each month.
The study, conducted by researchers at SE Ranking, a search engine optimisation platform, analysed over 50,000 health-related searches in Germany. The findings were alarming – YouTube accounted for 4.43% of all citations made by Google AI Overview, far outpacing any hospital network, government health portal, medical association or academic institution.
“This matters because YouTube is not a medical publisher,” the researchers wrote. “It is a general-purpose video platform. Anyone can upload content there, including board-certified physicians and hospital channels, but also wellness influencers, life coaches, and creators with no medical training at all.”
The study’s findings come after a previous Guardian investigation uncovered instances where Google AI Overview provided false and misleading health information, potentially putting people at risk of harm. In one case, the system gave bogus information about crucial liver function tests that could have led people with serious liver disease to wrongly believe they were healthy.
While Google has stated that AI Overview is designed to surface high-quality content from reputable sources, the research suggests that the system’s heavy reliance on YouTube calls this claim into question. The next most cited sources were the German public broadcaster NDR.de, the medical reference site Medmanual.com, and the consumer health portal Netdoktor.de.
Hannah van Kolschoten, a researcher specialising in AI, health and law at the University of Basel, who was not involved in the study, said the findings provide “empirical evidence that the risks posed by AI Overview for health are structural, not anecdotal.”
“It becomes difficult for Google to argue that misleading or harmful health outputs are rare cases,” van Kolschoten added. “Instead, the findings show that these risks are embedded in the way AI Overview are designed.”
Google has defended its use of YouTube, stating that the study showed the majority of the most cited YouTube videos were from medical channels. However, the researchers cautioned that these videos represented less than 1% of all the YouTube links cited by AI Overview on health-related queries.
As the use of AI-powered search tools continues to grow, this study serves as a wake-up call for the need to ensure that these systems prioritise reliable, authoritative health information from medical professionals and institutions, rather than relying heavily on unvetted sources like YouTube.
