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Spirulina · Arthrospira platensis
Herbs & Plants
Spirulina
Arthrospira platensis
Spirulina is not a plant and not quite an algae — it is a cyanobacterium, grown in shallow ponds and dried. What you buy is the whole organism with nothing taken out, which is unusual for anything sold in a tub.
Benefits
The harmful kind falls and the helpful kind rises, on a few grams a day of the plain powder.
What It Is Known For
It is protein-rich, and a few grams a day is a few grams. It is a supplement, not a food that will feed anybody.
The heavy-metal story runs in both directions here: badly grown spirulina is a source of them rather than a cure for them.
Widely sold on it, and not what the work behind this page measured.
Key Active Compounds
Grown, harvested and dried. Nothing is separated out.
The blue pigment, and what an extract would be sold as.
How to Take It / Use It
Take one to four grams of powder a day, stirred into something you will actually drink. It stains everything it touches, teeth included, so drink it down and rinse.
Cautions
Spirulina taken from open lakes can carry toxins made by the algae growing alongside it.
Spirulina is largely protein, and that rules it out for anyone who has to count phenylalanine.
Where It Comes From
Arthrospira grows naturally in warm alkaline lakes — Texcoco in Mexico, Chad in west Africa — where it was skimmed off the surface and dried into cakes long before anyone farmed it. Almost all of what is sold now is pond-grown.
How We Choose It
We check every product so you don't have to. A spirulina only makes our list if:
- Arthrospira platensis on the label. Blue-green algae is a category, not a species, and some of what is sold under it is a different organism entirely.
- Pond-grown, and it says where. A producer who names the farm is a producer you can ask about the water.
- Tested for microcystins and heavy metals, with the results published. This is the one product on this site where the growing water is the whole safety question.
- Powder rather than tablets, if you can stand it. The powder is what did best in the work behind this page, and a tablet needs binders to hold it together.
- Not a phycocyanin extract. That is the blue pigment pulled out and sold on its own, and it is not what was measured.
If no product meets these standards, we don't list one. No exceptions for affiliates.
See our picks
Sources2
- Effects of spirulina supplementation alone or with exercise on cardiometabolic health in overweight and obese adults: a systematic review and meta-analysis. Frontiers in Nutrition, 2025. Meta-analysis, 23 studies, 1035 people
- The effect of Spirulina supplementation on lipid profile: GRADE-assessed systematic review and dose-response meta-analysis. Pharmacological Research, 2023. Dose-response meta-analysis