Dietary supplement. For over 30 years Spirulina (Arthrospira platensis) has been the premier choice for supplementing a vegetarian diet. Source Naturals Spirulina is of the highest quality available. This special blue-green algae is a good source of numerous vitamins, minerals, carotenoids, and essential fatty acids that are hard to maintain at adequate levels with a vegetarian diet. Most notable is the high quality protein, which contains all nine essential amino acids. Spirulina's cell walls do not contain cellulose to slow down digestion. Source Naturals Spirulina is naturally grown and harvested without herbicides or pesticides.