A blue-green cyanobacteria, or algae, spirulina was consumed by Aztecs and has been touted by scientists as a potential outer-space meal replacement because it is so packed with nutrients. But spirulina has unique properties even among superfoods. For example, one study showed that spirulina decreases both the spread of the flu and the risk of death from flu viruses. Furthermore, when consumed with a probiotic, both the spirulina and the probiotic are more effective. As a final advantage, spirulina is more sustainable and environmentally friendly than almost any other source of nutrition, requiring minimal land and resources to produce. It might be the super-est superfood of them all.