Spirulina is an algae, and one of the most complete foods on the planet. It is a rich source of protein. This protein is abundant in all nine of the essential amino acids (those we cannot make for ourselves and so have to obtain from food). Spirulina also provides several highly-concentrated vitamins and minerals. Centuries ago the Aztec civilisation cultivated it as a staple food, and today it is regarded as central to some Asian diets. Although it can grow in natural conditions, most Spirulina today is produced commercially.

Spirulina replicates itself by photosynthesis, extracting energy from light. The product of this is chlorophyll, the substance that makes plants green. Another pigment in Spirulina is Phycocyanin. The protein content of Spirulina makes it popular with people following fitness regimes. Of equal value is the vitamins it provides.