Blue green algae, particularly species such as Spirulina and Aphanizomenon flos-aquae, are commonly marketed as supplements to boost energy levels and combat fatigue. The rationale is largely based on their nutrient content—blue green algae are rich in protein, B vitamins (especially B12, though the bioavailability is debated), iron, and various phytonutrients. Several small clinical studies and animal models have explored these algae for their potential to improve physical performance or reduce feelings of tiredness. For example, some randomized controlled trials have reported modest improvements in exercise endurance, reduction in fatigue, or increased perceived energy in healthy adults using spirulina supplements. However, these studies often have small sample sizes, short durations, and sometimes methodological limitations.

Systematic reviews generally conclude that while blue green algae are nutrient-dense and may provide some benefit in populations at risk of deficiencies, the evidence supporting their use specifically for increasing energy in healthy, non-deficient individuals remains limited and inconclusive. The effect, when present, may relate more to correcting mild nutrient deficiencies than to a direct “energizing” property of the algae. More robust, large-scale studies are needed to confirm any direct effect on energy levels or fatigue. Therefore, while there is some scientific investigation and plausible mechanisms, the overall strength of evidence is currently rated as low to moderate.