Spirulina
Arthrospira platensis (formerly Spirulina platensis; also classified as Limnospira)
A protein-rich blue-green algae with small, inconsistent effects on cholesterol and blood pressure.
Evidence tier
Preliminary
Research weight
Citations
16 verified / 16
Classification
Gut & Immune
❝
What the evidence says. Early or small human trials; promising but not yet conclusive.
What is Spirulina?
Spirulina (Arthrospira platensis (formerly Spirulina platensis; also classified as Limnospira)) is a gut and immune supplement used for modest lipid improvements: meta-analyses report lower ldl, total cholesterol and triglycerides with higher hdl, but trials are small and short and effect sizes vary widely.. NutriDex grades the human evidence as Preliminary. Spirulina is dried biomass of the cyanobacterium Arthrospira platensis, marketed as a protein and antioxidant supplement. Recent meta-analyses of mostly small, short randomized trials suggest it can modestly lower LDL, total cholesterol and triglycerides and produce small blood-pressure reductions, with the largest effects in people who have hypertension or elevated cardiometabolic risk. However, the trials are heterogeneous and the quality of evidence is generally only moderate, and a 2025 adjuvant-therapy review judged the cardiovascular effects small and of uncertain clinical significance. It is a genuinely nutrient-dense food (high-quality protein, B vitamins, iron, and the pigment phycocyanin), but its disease-relevant benefits remain preliminary rather than established. A key practical concern is product quality: poorly sourced spirulina can be contaminated with hepatotoxic microcystins, other cyanotoxins, or heavy metals, so third-party-tested products are important.
Purported Benefits
✓Modest lipid improvements: meta-analyses report lower LDL, total cholesterol and triglycerides with higher HDL, but trials are small and short and effect sizes vary widely.
✓Small reductions in blood pressure (roughly 3-4 mmHg systolic / 2-3 mmHg diastolic), most apparent in people with hypertension, overweight, or baseline BP at or above 120/80.
✓High-quality complete protein (~60-70% by weight) plus B vitamins, iron and antioxidant pigments, making it a useful nutrient-dense food rather than a proven therapeutic.
✓Phycocyanin and other constituents show antioxidant and anti-inflammatory activity in lab and animal models, but human outcome evidence remains preliminary.
✓Note: at least one 2025 umbrella/adjuvant review found the cardiometabolic effects 'small and of uncertain clinical significance,' so benefits should be considered supportive at best, not a substitute for proven therapies.
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Lipid improvements (LDL, TC, triglycerides, HDL)GRADE MAs show lower LDL/TC/TG and higher HDL, but a 2025 adjuvant review found no significant lipid change. | Mixed | ↔ mixed · small | 4 |
| Blood pressure reductionMAs show SBP ~-4 mmHg, DBP ~-3 mmHg, largest in hypertensive/overweight/older adults; GRADE moderate. | Moderate | ↑ benefit · small | 3 |
| Body weight / BMI / body fatGRADE high-certainty MA found weight -1.07 kg and body fat -0.84%, stronger at >=2 g/day beyond 12 weeks. | Moderate | ↑ benefit · small | 2 |
| Fasting glucose in type 2 diabetesMAs show FPG drop (~18 mg/dL) but no effect on HbA1c or postprandial glucose; small short trials. | Preliminary | ↑ benefit · small | 2 |
| Inflammation (CRP)One dose-response MA found CRP -0.55 mg/L with no dose/duration relationship; antioxidant signals marginal. | Preliminary | ↑ benefit · small | 1 |
| Hemoglobin in anemic pregnant womenGRADE-moderate MA found higher Hb, but mainly single-arm pooling with only a non-significant edge over iron. | Preliminary | ↑ benefit · moderate | 1 |
Dosing & Compounds
Typical Dose
Commonly 1-8 g/day (some trials up to ~10 g/day) of dried Arthrospira, in divided doses; cardiometabolic trials typically run 2-12 weeks. No established optimal or long-term safe dose.
Active Compounds
Safety & Cautions
Generally well tolerated short-term; mild GI upset, headache, or allergic-type reactions can occur. The main safety issue is product quality: poorly sourced or wild-harvested spirulina (and blue-green algae blends containing Aphanizomenon/Microcystis) may be contaminated with hepatotoxic microcystins, other cyanotoxins, or heavy metals (arsenic, lead, mercury, cadmium) — choose products independently tested for these. Because spirulina may stimulate immune activity, people with autoimmune diseases (e.g., lupus, MS, rheumatoid arthritis) should be cautious and consult a clinician; it should be avoided by anyone with the metabolic disorder phenylketonuria (PKU) due to its phenylalanine content. It can theoretically add to the effects of blood-pressure-lowering and anticoagulant/antiplatelet medications and may interact with immunosuppressants, so monitor if combined. Safety in pregnancy and breastfeeding is not established (contamination risk in particular), and long-term safety data are lacking; people who are immunocompromised, pregnant, or breastfeeding should avoid it unless cleared by a healthcare provider. Not a substitute for prescribed lipid- or blood-pressure-lowering therapy. Educational only — always check with your doctor or pharmacist before combining Spirulina with any medicine.
Spirulina drug interactions
Known or theoretical interactions between Spirulina and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Spirulina with any medicine.
Monitor
Immunosuppressants
Immune-stimulating activity may theoretically oppose immunosuppressant therapy.
Spirulina can enhance cytokine and immune-cell activity, counteracting immunosuppression. Spirulina as a biological response modifier (review)
Key Studies ★ 16 studies
Meta-analysis
Shiri 2025
✓ PubMed
RCT meta-analysis (searched through Jan 2025) reported spirulina improved lipid profile (lower TG, TC, LDL-C; higher HDL-C), reduced SBP/DBP, lowered weight/BMI, and improved glycaemic and inflammatory cardiovascular risk markers.
Systematic review
Cardiometabolic SR 2025
✓ Full text
Systematic review/meta-analysis of 23 studies (n=1,035) in overweight/obese adults found spirulina (alone or with exercise) significantly reduced LDL-C, total cholesterol, and triglycerides, with no significant change in fasting glucose or insulin.
Meta-analysis
Ghanbari et al. 2021 (systematic review & meta-analysis, 7 clinical + 27 preclinical)
✓ PubMed
Pooled clinical data showed Arthrospira (Spirulina) significantly reduced fasting blood sugar (-1.77), total cholesterol (-2.54), and triglycerides (-3.71) and raised HDL-C (+2.27), but did not significantly change HbA1c or LDL-C; FBS reductions were strongest at <2 g/day doses and <2 months.
GRADE-assessed systematic review and dose-response meta-analysis of RCTs
20 RCTs, 23 arms, 1,076 participants
✓ PubMed
Spirulina supplementation significantly reduced LDL-C, total cholesterol and triglycerides (each SMD about -0.6) and modestly raised HDL-C (SMD +0.3) versus control.
GRADE-assessed systematic review and meta-analysis of RCTs
RCTs in adults (meta-analysis)
✓ PubMed
Spirulina reduced systolic BP by about 4.41 mmHg and diastolic BP by about 2.84 mmHg, with larger effects in hypertensive, overweight, older (>50 y) participants and trials longer than 8 weeks; GRADE moderate quality.
Systematic review and meta-analysis of RCTs
5 RCTs, 230 subjects
✓ Full text
Spirulina (1-8 g/day, 2-12 weeks) significantly lowered systolic BP by about 4.59 mmHg and diastolic BP by about 7.02 mmHg, with effects concentrated in hypertensive patients.
Systematic review and meta-analysis of RCTs (Nutrients)
9 spirulina RCTs (101-299 participants per outcome)
✓ Full text
As a cardiovascular adjuvant, spirulina produced only a small significant reduction in diastolic BP (SMD -0.42) and no significant lipid changes, with authors concluding the effect is small and of uncertain clinical significance.
meta-analysis
17 RCTs, 888 adults (GRADE-assessed, dose-response)
✓ PubMed
Spirulina supplementation significantly reduced body weight (WMD -1.07 kg) and body fat percentage (WMD -0.84%) with GRADE high certainty, and BMI (WMD -0.40 kg/m2, moderate certainty), with stronger effects at doses >=2 g/day and durations >12 weeks in obese individuals.
meta-analysis
8 studies (9 arms), type 2 diabetes patients
✓ PubMed
In type 2 diabetes, spirulina (0.8-8 g/day for 45-90 days) significantly lowered fasting blood glucose by about 17.9 mg/dl plus triglycerides and total cholesterol, but had no significant effect on HbA1c or postprandial blood glucose.
meta-analysis
7 RCTs, 283 subjects, 10 effect sizes (dose-response)
✓ Full text
Spirulina supplementation significantly reduced serum C-reactive protein (WMD -0.55 mg/L; 95% CI -0.90 to -0.21; p=0.002), with no significant linear or non-linear dose- or duration-response relationship.
meta-analysis
9 controlled trials, 415 subjects
✓ PubMed
As an antioxidant adjuvant, spirulina produced only marginally significant increases in total antioxidant capacity (SMD 0.49; p=0.05) and superoxide dismutase activity (SMD 0.72; p=0.06), and no significant change in glutathione peroxidase (SMD 0.27; p=0.29).
meta-analysis
4 studies, 1,070 anemic pregnant women (GRADE moderate)
✓ Full text
Spirulina supplementation significantly raised hemoglobin in anemic pregnant women (single-arm pooled MD +1.81 g/dL; 95% CI 0.24-3.39; p=0.024), with a non-significant trend toward higher hemoglobin than standard iron (MD +1.45 g/dL; p=0.088).
meta-analysis
23 studies (28 trials), 1,035 overweight/obese adults
✓ Full text
Combining spirulina with exercise improved lipids more than exercise alone, significantly increasing HDL-C (Hedges g +1.08) and lowering LDL-C (g -0.81), while spirulina alone reduced total cholesterol, triglycerides, LDL-C and diastolic BP but did not improve glucose control.
guideline
NIH LiverTox drug-induced liver injury database
✓ Full text
NIH LiverTox classifies spirulina as having a generally favorable safety profile but implicated in rare cases of clinically apparent, usually self-limiting liver injury (mild enzyme elevations to hepatitis), with no reports of acute liver failure and possible confounding from contamination or co-ingested herbs.
rct
RCT, 150 allergic rhinitis patients (129 analyzed)
✓ PubMed
In a 6-month double-blind placebo-controlled trial, spirulina 2 g/day significantly improved nasal discharge, sneezing, nasal congestion and itching versus placebo (all p<0.001).
Contamination/safety surveillance study (Toxins)
623 dried + 105 culture samples from 95 producers (2013-2021)
✓ PubMed
Over 99% of French spirulina samples stayed below the 1 ppm MC-LR regulatory limit for microcystins, but 14 cyanobacterial contaminant taxa were detected, underscoring that contamination risk depends on production quality.