Spirulina and Chlorella Dietary Supplements—Are They a Source Solely of Valuable Nutrients?

<i>Spirulina</i> and <i>Chlorella</i> are nutrient-rich microalgae widely consumed as dietary supplements; however, their high biosorption capacity raises concerns regarding the accumulation of environmental contaminants. This study analyzed 52 commercially available <i>Spirulina</i> and <i>Chlorella</i> products (29 conventional, 23 organic) to assess the co-occurrence of heavy metals and pharmaceutical residues, as these two classes of contaminants represent distinct yet complementary indicators of environmental pollution-heavy metals reflect long-term inputs from natural and industrial sources, while pharmaceuticals signal more recent contamination linked to human activity and wastewater discharge. To the best of our knowledge, this is the first study to investigate the presence of pharmaceutical residues-including cardiovascular drugs, antidepressants, antibiotics, and sulfonamides-in both conventional and organic formulations of microalgae-based dietary supplements. The analyses were performed using Inductively Coupled Plasma Mass Spectrometry and liquid chromatography coupled to tandem mass spectrometry. Aluminum, manganese, strontium, and zinc were the dominant trace elements. All samples complied with EU regulatory limits for toxic metals. More importantly, a wide range of pharmaceutical residues was detected in the supplements. Caffeine was the most frequently found compound, followed by metronidazole, carbamazepine, benzocaine, and tramadol. Particular concern is raised by the calculated TWI (% of tolerable weekly intake) for aluminum. Principal Component Analysis revealed significant compositional differences between <i>Spirulina</i> and <i>Chlorella</i> products, with vanadium notably elevated in conventionally cultivated <i>Spirulina</i>. Surprisingly, no significant differences were observed between organic and conventional products within each algal type. Our findings provide a novel contribution to the field by highlighting the presence of pharmaceutical residues in microalgae-based supplements and addressing a critical knowledge gap concerning potential chronic exposure to these contaminants through dietary intake.