Spirulina contains compounds with antibacterial properties, as well as complex carbohydrates and polyphenols capable of stimulating the growth of certain microbes. Preclinical research suggests that spirulina may inhibit the growth of some potentially pathogenic microorganisms (e.g., Escherichia coli, Staphylococcus aureus, Candida albicans) while supporting the growth of microorganisms generally thought to be beneficial (e.g., those in the Lactobacillus and Bifidobacteria genera).[1]
While this suggests that spirulina has the potential to beneficially impact the gut microbiome, there is currently no research exploring this in humans.