Spirulina
Evidence Fact Sheet
Spirulina (Arthrospira platensis/maxima) is a nutrient-dense cyanobacterium whose active C-phycocyanin scavenges reactive oxygen species and modulates NF-kB and lipid metabolism. Human meta-analyses studied it for blood pressure, blood lipids, glycemic and inflammatory markers, with mixed findings. GRAS in the US; legal supplement in EU/BR/CN; no authorized health claims.
Also known as: Arthrospira platensis · Arthrospira maxima · C-phycocyanin (key active)
Overview
Spirulina is the dried biomass of the cyanobacteria Arthrospira platensis and A. maxima, marketed as a nutrient-dense plant protein and antioxidant supplement. Its principal active, C-phycocyanin, is proposed to scavenge reactive oxygen species, inhibit NADPH oxidase, and down-regulate NF-kB/COX-2 signaling, with additional reported effects on lipid metabolism and endogenous antioxidant enzymes. Most randomized trials use roughly 1-8 g/day (a 2-4 g/day range covers the majority of studied endpoints), divided with meals over 4-12 week windows. It is FDA GRAS (GRN 127) and a lawful dietary-supplement ingredient under DSHEA, legal as a food/supplement in the EU and listed by ANVISA in Brazil (daily limit <=5.7 g/serving), with a key quality caveat: closed-culture GMP sourcing is needed to avoid microcystin contamination (BR limit <=1 ug/g), and its pseudovitamin-B12 must not be claimed as a B12 source. No market authorizes disease-treatment health claims.
Mechanism of Action
C-phycocyanin scavenges reactive oxygen species and inhibits NADPH oxidase, attenuating oxidative stress in human supplementation studies · Down-regulates NF-kB signaling and COX-2, associated with reduced circulating CRP in pooled analyses · Modulates lipid metabolism (proposed up-regulation of LDL-receptor and reduced intestinal cholesterol absorption), correlating with observed reductions in total and LDL cholesterol · Increases endogenous antioxidant enzyme activity (e.g. SOD) and lowers MDA in randomized trials · Immunomodulatory effects on innate immune cells reported in small early-phase studies (preliminary)
Body systems: Cardiovascular · Immune System · Endocrine & Metabolic · Musculoskeletal · Blood & Hematopoiesis
Evidence-Based Benefits
Each benefit below is anchored to a specific PubMed-indexed study. Effect sizes, sample sizes, and p-values are reported as published; no values are inferred. Honest negatives and null results are kept alongside the positive findings, and disease-research populations are described as such — Spirulina is not characterized as a treatment for any disease.
Blood pressure
Meta-analysis supported- −4.59 mmHgsystolic · 95% CI −8.20 to −0.99
- −7.02 mmHgdiastolic · 95% CI −8.86 to −5.18
- 5 RCTs / 230trials · participants (SBP)
A meta-analysis of randomized controlled trials found spirulina supplementation was associated with modest but statistically significant reductions in both systolic and diastolic blood pressure, with the effect most apparent in hypertensive participants. This is a research finding on a biomarker, not evidence of treating hypertension.
Reported effect: SBP MD −4.59 mmHg (95% CI −8.20 to −0.99); DBP MD −7.02 mmHg (95% CI −8.86 to −5.18); 5 RCTs / 230 subjects (SBP)
“Spirulina intake led to a significant lowering of SBP (MD: −4.59 mmHg, 95% CI: −8.20 to −0.99, I2 = 65%) ... highly significant lowering of DBP in the Spirulina group (MD: −7.02 mmHg, CI: −8.86 to −5.18, I2 = 11%)”
Source: PMID 34578932 · Machowiec 2021 · Nutrients
Blood lipids
Meta-analysis supported- −46.76 mg/dLtotal cholesterol · p<0.001
- −41.32 mg/dLLDL-C · p<0.001
- 7 RCTspooled trials
A meta-analysis of 7 randomized controlled trials reported significant reductions in total cholesterol, LDL-C and triglycerides and a rise in HDL-C with spirulina supplementation. Effect sizes were large but heterogeneous across the small trial set, so the numbers describe pooled study outcomes rather than a clinical lipid-lowering claim.
Reported effect: TC WMD −46.76 mg/dL (95% CI −67.31 to −26.22); LDL-C −41.32 mg/dL; TG −44.23 mg/dL; HDL-C +6.06 mg/dL; 7 RCTs
“Random-effect meta-analysis of data from 7 RCTs showed a significant effect of supplementation with spirulina in reducing plasma concentrations of total cholesterol (WMD: -46.76 mg/dL, 95% CI: -67.31 to -26.22, p < 0.001), LDL-C (WMD: -41.32 mg/dL, 95% CI: -60.62 to -22.03, p < 0.001) and triglycerides (WMD: -44.23 mg/dL, 95% CI: -50.22 to -38.24, p < 0.001), and elevating those of HDL-C (WMD: 6.06 mg/dL, 95% CI: 2.37-9.76, p = 0.001).”
Source: PMID 26433766 · Serban 2016 · Clin Nutr
Blood lipids (dose-response confirmation)
Meta-analysis supported- SMD −0.6LDL-C · P<0.05
- SMD 0.3HDL-C · P<0.05
- 20 studies / 1076studies · participants
A larger, GRADE-assessed dose-response meta-analysis (20 studies, 23 arms, 1076 participants) corroborated the lipid signal, reporting significant standardized reductions in LDL-C, total cholesterol and triglycerides and a smaller increase in HDL-C. It is reported as a standardized effect size on pooled lipid endpoints.
Reported effect: LDL-C SMD −0.6 (95% CI −0.9 to −0.2); TC SMD −0.6; TG SMD −0.6; HDL-C SMD 0.3 (95% CI 0.0 to 0.6); 20 studies / 1076 participants
“20 studies (with 23 arms and 1076 participants) ... LDL-C: significantly reduced (SMD: -0.6, 95% CI: -0.9, -0.2, P<0.05) ... HDL-C: significantly increased (SMD: 0.3, 95% CI: 0.0, 0.6, P<0.05)”
Source: PMID 37263369 · Rahnama 2023 · Pharmacol Res
Glycemic markers (type 2 diabetes)
Null / no benefit Meta-analysis supportedA meta-analysis in people with type 2 diabetes found spirulina was associated with a significant reduction in fasting blood glucose, but reported NO significant effect on HbA1c or post-prandial blood sugar — an honest negative on the longer-term glycemic marker. Findings are biomarker changes in studied populations, not diabetes treatment.
Effect size: not quantified on this page — see the linked study below for the reported figures.
Source: PMID 34178867 · Hatami 2021 · J Diabetes Metab Disord
Inflammation (C-reactive protein)
Meta-analysis supported- −0.55 mg/LCRP · 95% CI −0.90 to −0.21
- p = 0.002pooled significance
- 7 trials / 283trials · subjects
A dose-response meta-analysis found spirulina supplementation significantly lowered serum C-reactive protein, a circulating inflammatory biomarker, versus control. This describes a biomarker change in pooled trials, not an anti-inflammatory disease claim.
Reported effect: CRP WMD −0.55 mg/L (95% CI −0.90 to −0.21; p = 0.002); 7 trials / 283 subjects / 10 effect sizes
“Spirulina supplementation significantly reduced serum CRP levels compared to the control group (WMD: −0.55 mg/L; 95% CI: −0.90 to −0.21; p = 0.002). ... 7 trials with 283 subjects and 10 effect sizes.”
Source: PMID 40330210 · Shahraki Jazinaki 2025 · Food Sci Nutr
Cardiovascular risk factors (mixed/null finding)
Null / no benefit Meta-analysis supported- −0.42diastolic BP · p = 0.04
- −0.17 (p=0.15)total cholesterol · NS
- 9 studiesspirulina arms
A more recent meta-analysis pooling spirulina and chlorella as cardiovascular adjuvants found spirulina significantly lowered diastolic blood pressure but did NOT significantly affect lipid (lipemia) indexes, only a non-significant trend toward lower total cholesterol. This tempers the older large lipid effect sizes and is an honest negative on the lipid endpoint.
Reported effect: DBP −0.42 (95% CI −0.81 to −0.02, p = 0.04); total cholesterol −0.17 (95% CI −0.39 to 0.06, p = 0.15, non-significant); 9 spirulina studies
“Spirulina intake led to a significant reduction in diastolic BP (−0.42, 95% CI: −0.81 to −0.02, p = 0.04) but did not significantly affect lipemia indexes, despite a trend toward a reduction in total cholesterol (−0.17, 95% CI: −0.39 to 0.06, p = 0.15).”
Source: PMID 40289965 · Pinto-Leite 2025 · Nutrients
Dosage (research context · not a recommendation)
1-8 g/day in most RCTs (consensus 2-4 g/day covers the majority of studied benefits); up to 8-10 g/day used in protein-supplementation contexts; typically divided into 2-3 doses with meals; intervention windows 4-12 weeks
Regulatory Status · 4 Markets
- US · FDA
- GRAS (GRN 127, no-objection letter); legal dietary supplement ingredient under DSHEA; structure/function claims only, no authorized health claims
- EU · EFSA
- Long history of consumption, not classified as Novel Food; legal as food and food supplement; NO authorized health claims
- BR · ANVISA
- Listed dietary-supplement ingredient (RDC 243/2018 + IN 28/2018) for A. platensis / A. maxima; daily limit <=5.7 g/serving; microcystin limit <=1 ug/g
Safety
Well tolerated at 2-10 g/day with decades of large-scale use. Common: mild GI upset/nausea at high initial doses; harmless pigment-related discoloration of urine/stool. KEY RISK: microcystin contamination from non-controlled or wild-harvested sources - require GMP closed-culture product with a certificate of analysis (BR limit <=1 ug/g). Contains pseudovitamin-B12 (low human bioavailability) - must NOT be claimed as a vitamin B12 source. Caution: PKU patients (high phenylalanine); autoimmune-disease patients (immune-stimulating effect); theoretical interaction with immunosuppressants and (via vitamin K) anticoagulants.
References
PubMed-indexed citations anchoring the benefit findings above. Effect sizes are reported as published.
- PMID 34578932 · Machowiec 2021 · Nutrients — Blood pressure
- PMID 26433766 · Serban 2016 · Clin Nutr — Blood lipids
- PMID 37263369 · Rahnama 2023 · Pharmacol Res — Blood lipids (dose-response confirmation)
- PMID 34178867 · Hatami 2021 · J Diabetes Metab Disord — Glycemic markers (type 2 diabetes)
- PMID 40330210 · Shahraki Jazinaki 2025 · Food Sci Nutr — Inflammation (C-reactive protein)
- PMID 40289965 · Pinto-Leite 2025 · Nutrients — Cardiovascular risk factors (mixed/null finding)
Frequently Asked Questions
1. What does the human evidence actually show for spirulina?
Meta-analyses of randomized trials report modest reductions in systolic and diastolic blood pressure (e.g. SBP −4.59 mmHg, DBP −7.02 mmHg), reductions in blood lipids, lower fasting blood glucose in type 2 diabetes, and reduced C-reactive protein. These are biomarker changes in studied populations, not evidence of treating any disease.
2. Are there honest negative findings?
Yes. In people with type 2 diabetes, spirulina lowered fasting blood glucose but showed no significant effect on HbA1c or post-prandial blood sugar. And a 2025 meta-analysis found spirulina lowered diastolic blood pressure but did not significantly affect lipid (lipemia) indexes, with only a non-significant trend (−0.17, p=0.15) for total cholesterol — tempering the large lipid effect sizes seen in older pooled trials.
3. How is spirulina dosed in the studies?
Most randomized trials use roughly 1-8 g/day, with a 2-4 g/day range covering the majority of studied endpoints, usually divided with meals over 4-12 week intervention windows. This is the research dose range observed in the literature, not a dosing recommendation — consult a qualified professional for personal use.
4. What are the main quality and safety considerations?
Spirulina is FDA GRAS (GRN 127) and a legal supplement in the US, EU and Brazil, with no authorized disease health claims. The key quality risk is microcystin contamination from non-controlled or wild-harvested sources, so closed-culture GMP product with a certificate of analysis is important (Brazil sets a microcystin limit of <=1 ug/g). Its pseudovitamin-B12 has low human bioavailability and must not be claimed as a vitamin B12 source; caution is noted for PKU and autoimmune conditions.
Last evidence review: 2026-06-27