Wikipedia er vist uenig:
Spirulina contains about 60% (51–71%) protein. It is a complete protein containing all essential amino acids, though with reduced amounts of methionine, cysteine and lysine when compared to the proteins of meat, eggs and milk.
Overall, while spirulina is often marketed as an excellent source of protein, it is no better in this regard than milk or meat (in that they are all complete proteins), and is approximately 30 times more expensive per gram of protein.
http://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)