Bioaccessibility studies of Fe, Cu and Zn from Spirulina dietary supplements with different excipient composition and dosage form

Context: The cyanobacteria Spirulina is a food supplement according to its high nutritional value. However, the bioaccesibility (Bac) of nutrients like Fe, Cu and Zn from Spirulina can be affected by excipients and formulations of supplements. Aims: To evaluate the Bac of Fe, Cu and Zn from different commercial presentations of Spirulina-based dietary supplements according to excipients and formulations. Methods: Microscopic studies were performed to study Spirulina content in dietary supplements. Total Fe, Cu and Zn concentrations were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Bac was calculated as the ratio between total metal concentration and the metal concentration after in vitro gastrointestinal digestion. Results: The Spirulina fragments concentration in the analyzed dietary supplements were different, corresponding to 2.21 × 109 – 4.46 × 109 cell fragments/g (p = 0.021; 95% confidence). Fe, Cu and Zn concentrations in Spirulina dietary supplements ranged from 63 ± 1 – 1066 ± 7 µg/g, 1.8 ± 0.1 – 187.9 ± 1.9 µg/g and 3.0 ± 0.3 – 57.3 ± 0.6 µg/g, respectively. Fe, Cu and Zn Bac were higher in the intestinal digestion stage in samples with high Spirulina count. Fe Bac was lower in tablets. Cu Bac was higher in the oral phase rather than the intestinal phase when Cu is present in excipients and not in Spirulina. Zn Bac decreases when Mg stearate is introduced as an excipient. Conclusions: The Bac of Fe, Cu, and Zn from Spirulina dietary supplements showed to be affected by excipients composition and by the solid dosage form. The different commercial presentations of Spirulina affect their nutritional value.