Nitrate, Nitrite, and Iodine Concentrations in Commercial Edible Algae: An Observational Study

Edible algae are a natural source of nutrients, including iodine, and can also contain nitrogen in the form of nitrate (NO₃^-) and nitrite (NO₂^-) as they can fix nitrogen from seawater. This study aimed to analyse the NO₃^-, NO₂^-, and iodine concentrations in eighteen macroalgae and five microalgae species commercially available in the United Kingdom. NO₃^- and NO₂^- concentrations were measured using high-performance liquid chromatography (HPLC), and iodine was determined using inductively coupled plasma mass spectrometry (ICP-MS). NO₃^- and iodine concentrations in macroalgae (NO₃^-: 4050.13 ± 1925.01 mg/kg; iodine: 1925.01 ± 1455.80 mg/kg) were significantly higher than in microalgae species (NO₃^-: 55.73 ± 93.69 mg/kg; iodine: 17.61 ± 34.87 mg/kg; p < 0.001 for both). In the macroalgae group, nori had the highest NO₃^- (17,191.33 ± 980.89 mg/kg) and NO₂^- (3.64 ± 2.38 mg/kg) content, as well as the highest iodine content. Among microalgae, Dunaliella salina had the highest concentration of NO₃^- (223.00 ± 21.93 mg/kg) and iodine (79.97 ± 0.76 mg/kg), while Spirulina had the highest concentration of NO₂^- (7.02 ± 0.13 mg/kg). These results indicate that commercially available edible algae, particularly macroalgae species, could be a relevant dietary source of NO₃^- and iodine.