For over 30 years spirulina (Arthrospira platensis) has been the premier choice for supplementing vegetarian diet Source Naturals Spirulina is one of the highest quality available. These special blue - green algae is a good source of numerous vitamins, minerals, carotenoids, and essentials fatty acids that are hard to maintain at adequate levels with a vegetarian diet. Most notable is the high quality protein, which contains cellulose to sloe down digestion. Source Naturals Spirulina is naturally grown and harvested without herbicides or pesticides.