Spirulina

What is spirulina?

Spirulina is a type of cyanobacteria, often called blue-green algae, that grows in warm alkaline lakes and is commercially farmed in ponds. The species most used are Arthrospira platensis and Arthrospira maxima. It is sold as a deep blue-green powder or tablet and is rich in protein, B vitamins, iron, carotenoids and phycocyanin, the pigment that gives it its color and much of its antioxidant activity.

What the research says

The strongest human evidence for spirulina concerns blood lipids. A 2023 GRADE-assessed systematic review and dose-response meta-analysis pooled 20 randomized controlled trials with more than 1,000 participants and found that spirulina supplementation significantly reduced LDL cholesterol, total cholesterol and triglycerides, and raised HDL cholesterol. Other meta-analyses have explored effects on blood pressure and body weight with mixed results. Most of these trials used daily doses in the range of grams, not milligrams.

Spirulina is sometimes marketed for brain health, energy and detox, including “pineal decalcification.” We found no good human evidence for these uses. Laboratory and animal studies suggest antioxidant and anti-inflammatory activity, but that has not translated into demonstrated cognitive benefits in people.

How it’s used in supplements

Spirulina is most often taken as powder in smoothies or as tablets, typically 1 to 8 grams per day. At these amounts it contributes protein and micronutrients. In a liquid formula taken by the drop, the amount would be too small to matter nutritionally.

Spirulina is generally safe when it comes from a reputable source. The main concern is contamination: blue-green algae harvested from uncontrolled environments can contain microcystins (liver toxins), heavy metals or harmful bacteria, so third-party testing matters. Spirulina can cause mild digestive upset. Because it may stimulate the immune system, people with autoimmune conditions such as lupus, multiple sclerosis or rheumatoid arthritis, or those taking immunosuppressive drugs, should avoid it unless their doctor agrees. People with phenylketonuria (PKU) should avoid it because it contains phenylalanine. Children and pregnant or breastfeeding women should use it only with medical advice, given the contamination risk.

Bottom line: spirulina is a legitimate nutrient-rich food with modest evidence for cholesterol, but it is not a memory supplement.

If you want to add spirulina to your diet, choose a product with independent testing for microcystins and heavy metals, start with a small amount, and treat it as a food rather than a treatment. People taking medications that suppress the immune system should ask their doctor first. Like chlorella, it is best judged by the grams you actually take, which a drop-based liquid product cannot provide.