Blue-green algae, particularly species like Spirulina, have been studied for their potential to support or treat anemia, especially iron-deficiency anemia. The scientific rationale is based on their high content of bioavailable iron and other nutrients such as vitamin B12, folic acid, and protein, all of which are important for red blood cell production. Several small clinical trials and animal studies have investigated this effect. For example, a randomized controlled trial published in Annals of Nutrition & Metabolism (2009) found that supplementation with Spirulina for school children in India resulted in a statistically significant improvement in hemoglobin levels compared to controls. Other studies have reported similar findings, though sample sizes are generally small and study durations short.

However, the overall quality of evidence is moderate to low due to limitations in study design, small sample sizes, and variability in Spirulina preparations. Furthermore, while some studies have shown improvements in iron status, others have failed to replicate these findings, and the effects may not be as pronounced as conventional iron supplementation.

In summary, there is some scientific evidence suggesting that blue-green algae, and Spirulina in particular, may be beneficial in supporting iron status and treating mild forms of anemia. However, the evidence is not robust enough to recommend it as a primary or sole treatment for anemia, especially in cases of moderate to severe deficiency.