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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.

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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.

How to take it

TimingTiming does not matter.
With food?Take with food, since algae powders commonly cause nausea on an empty stomach.
Worth knowingOnly buy batches with a published microcystin test result — AFA is harvested from open lakes where toxin-producing cyanobacteria bloom alongside it, and contaminated product has repeatedly reached the market.

Frequently asked questions

Is AFA blue-green algae safe?

AFA blue-green algae is harvested from Klamath Lake alongside toxin-producing cyanobacteria, and a laboratory survey found microcystins, which are liver toxins, in AFA products, several above tolerable daily intake. Avoid it with liver disease, in pregnancy, breastfeeding and children, and only buy batches with a published microcystin test.

Is AFA blue-green algae a good source of vitamin B12 for vegans?

No, that is unproven: a tiny uncontrolled pilot study reported a rise in serum B12, but most B12 in cyanobacteria like AFA is present as analogues humans cannot use.

What are the benefits of AFA blue-green algae?

The human evidence for AFA blue-green algae amounts to a couple of small, weak studies, so any benefit is unproven (limited grade). The best-documented fact about it is cyanotoxin contamination, which is a risk rather than a benefit.

How much AFA blue-green algae per day?

The typical label dose of AFA blue-green algae is 1–3 g/day of dried algae, but no dose has been validated for any health outcome. Take it with food to reduce nausea.

Scientific references

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