Spirulina gained popularity after NASA utilized it as a dietary supplement for astronauts. It grows in harsh environments where the majority of aquatic life cannot exist. In addition to being rich in protein (up to 70%), spirulina provides vitamins, minerals—particularly iron—and plant-based compounds such as zeaxanthin, a carotenoid. Interesting note: contrary to common belief, spirulina is a cyanobacterium rather than an algae.