No matter how amazing a supplement might be, don't forget that nothing can substitute a balanced diet. Spirulina is a great ally for vegans, as it can help them increase their nutritional intake. Still, a vegan's overall diet should be carefully planned and supervised by a nutritional expert.
That said, this micro-algae is a great source of protein for vegans. That's because spirulina is made up of proteins with high biological value. They contain the essential amino acids that your body can't produce on its own. Spirulina is also rich in iron, folate and zinc, nutrients that are commonly lacking in vegan diets.
Vegans can significantly improve their nutrition when they combine spirulina with a balanced diet.