How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Spirulina
A microalgae that slightly lowers LDL, triglycerides, and blood pressure in meta-analyses; regarding weight, memory, and sports performance, a few trials with mixed results.
Benefits
- Lowers LDL, total cholesterol, and triglycerides, and raises HDL: meta-analysis of 20 trials involving 1,076 participants (2023), consistent with a meta-analysis of 7 trials (2016)
- Lowers systolic and diastolic blood pressure: meta-analysis of 5 trials involving 230 people (1 to 8 g per day), a clearer effect in hypertensive individuals; the 2025 meta-analysis confirms this, especially beyond 8 weeks and after 50 years of age
- In 40 overweight hypertensive individuals, 2 g per day for three months lowered systolic pressure and weight, and improved vessel function (placebo-controlled trial)
- In type 2 diabetics, reduces fasting blood glucose and improves blood lipids (meta-analysis of 8 trials); 8 g per day for 12 weeks lowered triglycerides in 37 patients
- Helps slightly with weight loss during dieting: in 52 overweight individuals, 2 g per day with a hypocaloric diet for 12 weeks reduced weight, waist circumference, and fat mass; the meta-analysis of 5 trials finds a decrease in weight especially in obese individuals
- In 80 elderly individuals with mild memory impairments, 1 g per day of a Spirulina maxima extract for 12 weeks improved visual learning, visual working memory, and vocabulary (placebo-controlled trial)
Precautions
The United States Pharmacopeia safety evaluation, which reviewed 31 adverse event reports, classifies Spirulina maxima and S. platensis as Class A, allowing their use as a dietary supplement ingredient; in the 12-week memory trial, no adverse effects were reported. Limitations: most trials involve overweight, hypertensive, diabetic, or elderly individuals, and meta-analyses on weight (5 trials) and blood pressure (5 trials, 230 people) remain small. Regarding oxidative stress and inflammation, the meta-analysis of 11 studies finds only marginal decreases, and the increase in interleukin-2 disappears upon sensitivity analysis. On the sports side, the review of 13 studies sees no performance improvement in strength athletes and deems the evidence on recovery limited and inconsistent; the positive performance trial involves only 9 men, and the muscle damage trial in 24 men finds nothing.
Recommended dosage
1 to 8 g per day in trials: 2 g for weight and blood pressure, 6 to 8 g for blood lipids and exercise capacity
How to take it
- Blood lipids: 8 g per day for 12 weeks in 37 diabetics and for 16 weeks in 78 elderly individuals; in the 2016 meta-analysis, the effect depends on duration, not dose.
- Blood pressure and weight: 2 g per day for 12 weeks in both trials involving overweight individuals; the 2025 meta-analysis observes a clearer effect beyond 8 weeks.
- Duration: on BMI, the 2021 meta-analysis only finds an effect after at least 12 weeks.
- Memory: 1 g per day of a Spirulina maxima extract for 12 weeks, in a single trial.
- Sports: 6 g per day for 4 weeks in 9 moderately trained men, 5.7 g per day for 7 weeks in 17 rugby players.
- What does not always work: in 24 trained men, 6 g per day did not change muscle soreness, muscle performance, or markers of damage after muscle-damaging exercise.
- Timing of intake: no study in this sheet compares morning and evening, nor intake during or between meals.
Did you know?
On cholesterol and triglycerides, the effect of spirulina depends on the duration of intake, not the dose: this is what the meta-analysis of 7 controlled trials finds.
What the studies say
This updated systematic review and meta-analysis concludes that Spirulina consumption decreases systolic and diastolic blood pressure in adults. The effects are more marked in individuals with high blood pressure, hypertensives, overweight individuals, those over 50 years old, and after more than 8 weeks of supplementation. Spirulina could be used in clinical practice for blood pressure management.
Shiri H, Yasbolaghi Sharahi J, Alizadeh Sani M, Mousavi SMJ, Nematollahi MH, Soleimani AA, Amri J, Panahi G. — Phytotherapy research : PTR (2025) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more