Limited evidenceGeneral health

AFA Blue-Green Algae

A wild-harvested cyanobacterium from Klamath Lake sold as a "superfood". Human data amount to a couple of small, weak studies, and independent analyses have repeatedly found cyanotoxins in commercial products.

Evidence last reviewed: August 2026

What the science says

Vitamin B12 status in vegans Limited evidence
A small pilot study in vegan subjects reported that a Klamath algae product raised serum B12 and lowered homocysteine. It was tiny and uncontrolled, and most B12 in cyanobacteria is present as analogues that humans cannot use, so this remains unproven.
Metabolic markers in type 2 diabetes Limited evidence
One small trial in people with type 2 diabetes reported changes in the metabolic profile after an AFA extract. It was a single low-quality study with no replication.
Cyanotoxin contamination is a real problem Limited evidence
A laboratory survey of algal dietary supplements detected microcystins in AFA-based products, several above tolerable daily intake levels. This is the best-documented fact about the supplement, and it is a risk rather than a benefit.

Dosage & safety

Studied doseTypical label dose is 1–3 g/day of dried algae. No dose has been validated for any health outcome.

SafetyAFA blooms co-occur with microcystin- and anatoxin-producing cyanobacteria, and contaminated batches have been found repeatedly on the market. Microcystins are liver toxins. Avoid if you have liver disease, and avoid in pregnancy, breastfeeding and children. If you use it, choose products with batch-level microcystin testing.

Scientific references

Effect of a Klamath algae product ("AFA-B12") on blood levels of vitamin B12 and homocysteine in vegan subjects: a pilot study
Baroni L, Scoglio S, Benedetti S — Int J Vitam Nutr Res, 2009
Consequences of AphanizomenonFlos-aquae(AFA) extract (Stemtech (TM) ) on metabolic profile of patients with type 2 diabetes
Sanaei M, Ebrahimi M, Banazadeh Z — J Diabetes Metab Disord, 2015
Toxin content and cytotoxicity of algal dietary supplements
Heussner AH, Mazija L, Fastner J — Toxicol Appl Pharmacol, 2012

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