Spirulina is a blue-green algae, and is believed to be one of the oldest life forms on Earth. First used by the Aztecs as an endurance-booster, spirulina is considered a superfood — an all-in-one source of nutrients including protein levels comparable to eggs. Spirulina is a potent source of nutrients. It contains a powerful plant-based protein called phycocyanin. Research shows this constituent may have antioxidant, pain-relief, anti-inflammatory, and brain-protective properties.