Risk Omission and Limited Disclosure in Dietary Supplement Promotion by Social Media Influencers

Importance: Dietary supplements carry risks including adverse effects, drug interactions, and contamination-related harms, yet are frequently marketed without premarket requirements for efficacy or safety. Social media influencers have become a primary source through which people encounter and make decisions about supplements, but whether they communicate clinically relevant risks alongside claimed benefits remains unclear. Objective: To investigate how dietary supplements are presented by Instagram influencers, focusing on supplement types, advertising disclosure, persuasive strategies, and communication of benefits and harms. Design, Setting, and Participants: Cross-sectional content analysis of 1,120 dietary supplement presentations in 727 Instagram posts by 84 influencer accounts identified through audience-centered purposive sampling from two independent youth-focused studies in Switzerland and Austria. Main Outcomes and Measures: Main outcomes were supplement types, overall tone, advertising disclosure, persuasive strategies, and communication of benefits and harms, all summarized descriptively. Logistic regression with cluster-robust standard errors assessed whether influencer type or supplement category influenced presentation characteristics. Results: Of 1,120 supplement presentations, 1092 (97.5%) were promotional in tone, 1088 (97.1%) involved advertising, but disclosure was absent in 802 advertisements (73.7%). Protein (463 [41.3%]), caffeine (156 [13.9%]), creatine (71 [6.3%]), and (multi-)vitamins (67 [6.0%]) were the most frequently identified ingredients. Benefits were mentioned in 269 presentations (24.0%); harms in only 26 (2.3%), mostly framing supplements as unnecessary or cautioning about side effects. No presentation mentioned drug interactions, contamination risks, or contraindications. Benefit claims were more common in presentations featuring micronutrient and miscellaneous ingredient supplements, and less common in presentations featuring sport nutrition supplements. Influencers with health credentials were more likely to include evidence cues than nonprofessionals (adjusted OR, 81.05; 95% CI, 13.76-477.44); associations with tone and personal experience narratives were not robust to adjustment. Conclusions and Relevance: Influencer presentation of supplements was highly commercialized, largely undisclosed, and characterized by a substantial imbalance between benefit and risk communication. The absence of clinically relevant risk information suggests that individuals relying on such content are unlikely to receive balanced safety information, underscoring the need for stronger regulation and proactive clinician inquiry about supplement use.