Spirulina has an antioxidant effect

In patients with human immunodeficiency virus (HIV) infection, the administration of spirulina increases the antioxidant capacity; in older adults it increases the antioxidant capacity; and it increases the ergogenic and antioxidant capacity in athletic subjects (Martínez-Sámano et al. 2018).

Reference:

Martínez-Sámano, J., et al. (2018). Spirulina maxima decreases endothelial damage and oxidative stress indicators in patients with systemic arterial hypertension: results from exploratory controlled clinical trial. Marine Drugs, vol. 16, no. 496.