IngredientsSpirulina algae, also known as Arthrospira platensis, are members of the class of cyanobacteria (also named blue-green algae) that are classified under the phylum of multicellular organisms. Spirulina is a dietary supplement prepared from the biomass of blue-green algae which is rich in protein, vitamins and minerals; "spirulina" refers to a large number of photosynthetic eubacterial species belonging to the phylum Cyanobacteria, primarily Arthrospira platensis and Arthrospira maxima.
While known as blue-green algae, spirulina is a prokaryotic, eubacterial species belonging to the phylum Cyanobacteria. Spirulina genus (cyanobacteria) is a prokaryotic microorganism, which distinguishes it fundamentally from eukaryotic microalgae such as Chlorella. Arthrospira species are free-floating, filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-handed helix; they occur naturally in tropical and subtropical lakes with high pH and high concentrations of carbonate and bicarbonate.
The common name "spirulina" refers to the dried biomass of A. platensis, which belongs to photosynthetic bacteria that cover the groups Cyanobacteria and Prochlorophyta; scientifically, a distinction exists between spirulina and the genus Arthrospira, for which the two species were originally proposed. In 2019 it was found that the cultivated species differ too much from the type species of Arthrospira to be in the genus, necessitating another batch of renaming to Limnospira to reflect biological reality. However, the name "spirulina" and "Arthrospira" remain the most widely used in commercial and scientific literature.
Beyond spirulina, other cyanobacteria also appear in the dietary supplement market. Blue-green algae species including Spirulina sp. and Aphanizomenon flos-aquae are commercially distributed as organic algae dietary supplements. The cyanobacterium Arthrospira is among the most well-known food supplements worldwide known as "Spirulina."
Species of Arthrospira have been isolated from alkaline brackish and saline waters in tropical and subtropical regions; among the various species, A. platensis is the most widely distributed and is mainly found in Africa, but also in Asia. A. platensis occurs in Africa, Asia, and South America, whereas A. maxima is confined to Central America. Besides Lake Texcoco, the largest Arthrospira lakes are in Central Africa around Lake Chad and Lake Niger, and in East Africa along the Great Rift Valley.
Most cultivated spirulina is produced in open-channel raceway ponds, with paddle wheels used to agitate the water. Its current commercial success is linked to its GRAS ("Generally Recognized as Safe") and similar agreements obtained within the different food and safety agencies worldwide. Spirulina now belongs to the substances that are listed by the US Food and Drug Administration under the category Generally Recognized as Safe (GRAS).
Currently, spirulina can be found in health food stores and is sold mainly as a dietary supplement in the form of health drinks or tablets. Studies have used a wide range of dosage forms including capsules, tablets, liquids, and sauces. Arthrospira platensis, also commonly called spirulina, is up to now the most cultivated cyanobacterium as human food, dietary supplement, natural blue dye, and bioactive molecule source for diverse applications.
The species Arthrospira geitleri was consumed during the pre-Columbian period by the Aztecs that lived near Lake Texcoco. Human consumption of A. platensis is known to date at least from the 16th century in America as part of the Aztec diet. Historians believe that the Aztecs harvested spirulina from Lake Texcoco around the 14th–16th centuries; they called it "tecuitlatl," which means "fecal stone" in Nahuatl, and used it as a nutrient-rich food source.
The waters of the lake had the perfect balance of salinity and alkalinity for spirulina to thrive; the Aztecs called it "tecuitlatl" ("stone excrement"). Aztecs skimmed it from lakes in the Valley of Mexico, including Lake Texcoco, with nets or shovels; once harvested, the Aztec sun-dried the algae and cut it into bricks; when preserved this way, it would remain edible for a year; the Aztecs called the algae tecuitlatl and ate it with tortillas or toasted corn. Spirulina was found in abundance at Lake Texcoco by French researchers in the 1960s, but no reference to its use by the Aztecs as a daily food source was made after the 16th century, probably because of the draining of the surrounding lakes for agriculture and urban development.
Danegard (1940) discovered that the Kanembou living around Lake Chad in Chad, Africa, harvested Arthrospira platensis for use as a food called "Dihé." In Africa, especially the area around Lake Chad, spirulina has been used as food by the Kanembu people for centuries; they harvest algae from natural alkaline lakes and dry them into cakes, which are then used in many traditional dishes. In 1940, a French botanist named Pierre Dangeard reported on the Kanembu people of Chad using spirulina as food; however, it was not until the 1960s that scientists began to further study this algae.
The traditional consumption of spirulina harvested in Lake Chad by the Kanembou led to the discovery of the nutritional richness of this cyanobacterium in the 1960s. The exceptional nutritive value of spirulina has led the United Nations Food and Agriculture Organization (FAO) to consider spirulina a food of major interest against malnutrition for food security and the response to emergency food situations.
In human nutrition, Arthrospira is mainly used for its high protein quality and concentration, which can reach 60%–71% of the dry matter. Dried spirulina typically contains 60–70% protein, 15–20% carbohydrates, 5–8% lipids, vitamins, minerals, essential fatty acids, β-carotene, and the rare essential γ-linolenic acid.
The genus Spirulina is one of the most prominent microalgae due to its high production of (I) Long-Chain Polyunsaturated Fatty Acids; (II) Phenolic Compounds; (III) Volatile Compounds; (IV) Sterols; (V) Proteins, Amino Acids, Peptides; (VI) Vitamins; (VII) Polysaccharides; (VIII) Pigments.
Cyano-phycocyanin is one of the active pigments of blue-green algae and is usually isolated from the filamentous cyanobacteria Arthrospira platensis Gomont (spirulina). The bright blue light-harvesting pigment phycocyanin, unique to cyanobacteria, is a known antioxidant and anti-inflammatory compound, in part due to its ability to inhibit the inflammatory enzyme cyclooxygenase-2 (COX-2). The dry biomass of certain strains contains up to 18% of C-PC (C-phycocyanin), while, based on the literature data, the dry biomass of spirulina generally constitutes 10–15% of C-PC.
C-phycocyanin (C-PC) is one of the major biliproteins of spirulina with antioxidant and radical scavenging properties; C-PC, a selective cyclooxygenase-2 inhibitor, induces apoptosis in lipopolysaccharide-stimulated macrophages and is known to exhibit anti-inflammatory and anticancer properties.
The antioxidant, anti-inflammatory, anti-tumour and anti-HCoV-229E activities are associated with the natural C-phycocyanin, a water-soluble blue protein-pigment complex and allophycocyanin, which reside in cyanobacterial cells.
The spirulina cell includes a wide variety of bioactive substances associated with phycocompounds like phenolic compounds, e.g., flavonoids, isoflavonoids, stilbenes, carotenoids especially lycopene, as well as polyterpenes, alkaloids, saponins, and steroids.
Spirulina contains a set of specific molecules — C-phycocyanin, complex polysaccharides such as calcium spirulan and γ-linolenic acid — which have strong prophylactic and therapeutic potential, especially in the fields of cardiovascular diseases, viral infections, cancer prevention and therapy, immune response, as well as diabetes and cholesterol control.
Radachlorin, a representative of chlorine photosensitizer extracted from S. platensis, has presented anticancer activity; and calcium spirulan (Ca-SP), a Ca2+-sulfated polysaccharide, has previously been recognized for its antiviral properties.
Spirulina contains various components that are beneficial for health, such as proteins, vitamins, essential amino acids, minerals, γ-linoleic acid, glycolipids, sulfolipids, and phycobilins (phycocyanin, allophycocyanin, and phycoerythrin). Numerous studies have suggested that zeaxanthin and lutein are crucial for visual health, and spirulina can serve as a rich source of dietary zeaxanthin in humans.
Cyanobacteria (blue-green algae) are an abundant source of structurally diverse and biologically active metabolites, including peptides (e.g., cryptophycins and microcystins), alkaloids (e.g., hapalindoles), and pigments (e.g., C-phycocyanin and scytonemin), many of which demonstrate promising anticancer and antimicrobial properties.
It has been well documented that spirulina exhibits anti-inflammatory properties by inhibiting the release of histamine from mast cells. C-phycocyanin's selective inhibition of COX-2 is regarded as a central anti-inflammatory mechanism. Because of its chemical structure, C-phycocyanin also exhibits antioxidant and free radical scavenging properties, which may contribute, at least in part, to its anti-inflammatory activities.
Research suggests that spirulina may regulate body weight and metabolic health by inhibiting macrophage migration to visceral fat, reducing hepatic fat accumulation, lowering oxidative stress, enhancing insulin sensitivity, and increasing satiety. Spirulina's tripeptides lower blood pressure, while gamma-linolenic acid and glycolipids improve lipid profile.
Data in the literature show that in mammalian cells, phycocyanin modulates AKT and AMPK signalling, ameliorating the senescence of mesenchymal stem cells and protecting against high-glucose and high-fat diet-induced diabetes in mice.
Spirulina can modulate the Th profile in patients with allergic rhinitis by suppressing the differentiation of Th2 cells, mediated in part by inhibiting the production of IL-4.
Cyanobacteria produce various anticancer compounds via mechanisms such as apoptosis induction, angiogenic inhibition, and immune response modulation; cryptophycins identified from Nostoc species act as cytotoxins with a potent capacity to disrupt microtubule assembly and inhibit cancer cell proliferation; curacin A of Lyngbya majuscula was found to interfere with the polymerization of tubulin, thus inhibiting cancer growth. Phycobiliproteins, particularly the phycocyanin extract from Spirulina platensis, hinder oxidative stress-induced tumor development because of their antioxidant and anti-inflammatory activities. These mechanisms have been demonstrated primarily in preclinical (in vitro and animal) settings.
Pooled results showed that spirulina supplements significantly lower total cholesterol, LDL-C, triglycerides, and VLDL-C; clinical trials have investigated the influence of spirulina on metabolic-related risk factors but have yielded conflicting results in humans.
A 2018 meta-analysis identified and analyzed 12 eligible trials. A total of 1,868 records were identified, of which 12 trials with 14 arms were eligible; the amount of spirulina ranged from 1 to 19 g/d, and intervention durations ranged from 2 to 48 weeks. Data synthesis showed that spirulina supplements significantly lowered total cholesterol (WMD = −36.60 mg/dL), LDL-C (WMD = −33.16 mg/dL), triglycerides (WMD = −39.20 mg/dL), VLDL-C (WMD = −8.02 mg/dL), fasting blood glucose (WMD = −5.01 mg/dL), and DBP (WMD = −7.17 mmHg).
A more recent meta-analysis drawing on 20 studies with 23 arms and 1,076 participants, searching until January 2023, reported: pooled results indicated that spirulina intervention significantly reduced LDL-C (SMD: −0.6), TC (SMD: −0.6), and TG (SMD: −0.6) levels while HDL-C levels were significantly increased (SMD: 0.3); the findings show the usefulness of supplementing with spirulina in improving serum levels of TC, TG, LDL-C, and HDL-C.
A 2025 meta-analysis of 35 RCTs confirmed these findings: results from 35 trials show that spirulina intake improved glucose homeostasis (FBG; WMD: −5.51 mg/dl), decreased dyslipidemia (TG; WMD: −14.75 mg/dl, TC: WMD: −11.5 mg/dl, LDL-C; WMD: −7.69 mg/dl, and HDL-C; WMD: 1.9 mg/dl), decreased blood pressure (SBP; WMD: −3.85 mmHg and DBP; WMD: −3.09 mmHg), reduced anthropometric indexes (weight; WMD: −1.78 kg, BMI; WMD: −0.58 kg/m²), and decreased inflammation (TNF-α, IL-6, and hs-CRP).
Evidence strength: Overall, five trials were considered as a low risk of bias, six as a high risk of bias, and one as unclear, indicating that while multiple meta-analyses show consistent directional effects on lipid parameters, the overall evidence base is limited by heterogeneous study designs, small sample sizes, and variable quality.
A GRADE-assessed systematic review and meta-analysis published in 2024 specifically evaluated blood pressure effects: spirulina consumption decreases systolic blood pressure (WMD: −4.41 mmHg, 95% CI: −6.74 to −2.07, I² = 66.1%) and diastolic blood pressure (WMD: −2.84 mmHg, 95% CI: −4.65 to −1.03, I² = 62.3%). Subgroup analysis demonstrated SBP and DBP were still lower in individuals with hypertension, overweight individuals, those aged over 50, and with interventions exceeding 8 weeks; based on GRADE, outcomes have moderate quality.
Spirulina significantly reduces DBP (~2.60 mmHg); a 2 mmHg reduction in DBP decreases hypertension prevalence by 17%, coronary heart disease risk by 6%, and stroke/transient ischemic attack risk by 15%; however, high heterogeneity limits certainty.
Selected studies have been performed in subjects who suffered from type 2 diabetes mellitus, HIV infection, hypertension, ischemic heart disease, and hyperlipidemic nephrotic syndrome. The 2018 meta-analysis confirmed a statistically significant reduction in fasting blood glucose (WMD = −5.01 mg/dL), though of modest absolute magnitude.
Research demonstrates that spirulina, as an adjunct to metformin, outperforms metformin alone in long-term blood glucose and lipid control in T2DM patients, without significant adverse effects or hepatic/renal complications.
Evidence strength: Trial durations varied significantly, from as short as 17 days to as long as one year, with shorter durations possibly insufficient to observe long-term effects; participant characteristics varied, including healthy individuals and those with metabolic syndrome, diabetes, hypertension, and obesity, affecting results' generalizability. The evidence is promising but heterogeneous, with several methodological limitations.
It has been well documented that spirulina exhibits anti-inflammatory properties by inhibiting the release of histamine from mast cells. In a key human clinical study, the impact of a Spirulina-based dietary supplement on patients with allergic rhinitis was evaluated by assessing the production of cytokines (IL-4, IFN-gamma, and IL-2) critical in regulating IgE-mediated allergy; in a randomized double-blinded crossover study versus placebo, allergic individuals were fed daily with either placebo or spirulina, at 1,000 mg or 2,000 mg, for 12 weeks. Spirulina administered at 2,000 mg/day significantly reduced IL-4 levels by 32% from PHA-stimulated cells.
A further double-blind, placebo-controlled study reported: spirulina consumption significantly improved the symptoms and physical findings compared with placebo (P < 0.001) including nasal discharge, sneezing, nasal congestion, and itching.
A systematic review found two clinical trials involving a total of 215 patients; both studies assessed the efficacy of spirulina in improving allergic rhinitis as the primary outcome. The positive effects of spirulina in allergic rhinitis are based on adequate evidence but larger trials are required.
The exceptional nutritive value of spirulina has led the FAO to consider spirulina a food of major interest against malnutrition for food security and the response to emergency food situations.
A prospective study conducted in the Democratic Republic of the Congo enrolled 50 children aged 6–60 months. The intervention group consisted of 16 children who received 10 g of spirulina daily as well as the local diet administered by the nutritional centre, and the control group of 34 children who received only the local diet; both groups were assessed on day zero, day 15, and day 30. After treatment, the weight-for-age Z scores and weight-for-height Z scores increased significantly in the intervention group; at day 15, there was a statistically significant difference between mean corpuscular volume, total proteins, and albumin (p < 0.05) in both groups, in favour of the intervention group.
Spirulina supplementation at a dose of 10 g per day was found to improve the nutritional status as well as to increase the corpuscular hemoglobin and hematocrit levels in malnourished children in the Democratic Republic of the Congo.
In studies involving HIV-positive malnourished populations: Azabji Kenfack and associates in 2011 examined the effect of daily spirulina intake for 12 weeks on 56 malnourished HIV-infected adult patients and concluded that spirulina consumption effectively improved weight and BMI among undernourished HIV sufferers.
A systematic review (CD4+ count in HIV patients) of seven clinical studies concluded that the available evidence indicates that spirulina might be useful to improve the CD4+ T-lymphocyte count in patients with HIV; a more pronounced effect is likely observed for a 10 g daily dose of spirulina for 6 months, while smaller amounts given for shorter periods seem less effective.
Regarding mortality outcomes in HIV, a Cochrane review found: neither supplementary food nor daily supplement of spirulina significantly altered the risk of death compared with no supplement or placebo in malnourished, ART-naïve adult participants in the studies which reported on this outcome.
The antioxidant and/or anti-inflammatory activities of spirulina were demonstrated in a large number of preclinical studies; however, a limited number of clinical trials have been carried out so far to confirm such activities in humans. To date, there are no in vivo human studies specifically on possible antioxidant effects of spirulina. Evidence for antioxidant benefits therefore remains primarily preclinical.
Spirulina's seaweed pigment can reduce obesity, body mass index (BMI), hypertension, hyperglycemia, and dyslipidemia. The 2025 multi-RCT meta-analysis confirmed a small but statistically significant reduction in body weight (WMD: −1.78 kg) and BMI (WMD: −0.58 kg/m²). The review also included both randomized and non-randomized clinical trials, with non-randomized trials being more prone to bias; there was variability in the outcomes measured, complicating direct comparisons.
It is believed that the anticancer effects of spirulina are perhaps derived from β-carotene, a known antioxidant; however, the link between β-carotene level and carcinogenesis cannot be established as the etiology of carcinoma is frequently multifactorial. Evidence for anticancer effects in humans remains very preliminary, with no robust clinical trials establishing therapeutic efficacy.
A systematic review examining antioxidant, anti-inflammatory, and immunomodulatory effects of spirulina in exercise identified several RCTs. Studies found mixed results, with some reporting benefits to redox status following muscle-damaging protocols and small improvements in vertical jump and sprint performance, though the overall evidence base is limited in size and quality.
Studies have used a wide range of dosages (20 mg–6 g) and forms (capsules, tablets, liquids, and sauces), making it difficult to establish a consistent treatment protocol. In the meta-analysis by Serban et al., the amount of spirulina used across trials ranged from 1 to 19 g/d, and intervention durations ranged from 2 to 48 weeks.
Specific doses reported in clinical studies by indication include:
Comprehensive clinical trials examining the safety of spirulina for humans are lacking; despite this, the long history of spirulina consumption by people, together with ample data from animal feeding trials, has led to acceptance of Arthrospira spp. as being safe for human consumption.
Spirulina has been implicated in isolated case reports in causing clinically apparent liver injury, but the role of spirulina as opposed to other herbal components or contaminants has not been shown; liver injury due to spirulina must be very rare if it occurs at all.
Cyanobacterial dietary products in particular have raised serious concerns, as they appeared to be contaminated with toxins e.g. microcystins (MCs), and consumers have repeatedly reported adverse health effects following consumption of these products. Among these classes, MCYSTs were found at concentration levels higher than 5 mg kg⁻¹; cyanotoxins were also detected in nine out of the thirty-five analyzed algal food supplements from the Belgian market, with contaminated products containing total MCYSTs of concentrations between 238.45 and 5645.33 µg kg⁻¹.
Greater attention needs to be given to the safety of spirulina products, particularly the use of open ponds, which are subject to external contamination and may allow the growth of other, toxin-producing species of cyanobacteria. All of the products examined in one study were contaminated with microcystins at a level which could, at least, contribute a significant proportion of the recommended safe intake of the consumer, and in some cases cause the limit to be exceeded even with no other dietary sources.
The French ANSES agency found: most products containing exclusively spirulina (Arthrospira spp.) that have undergone contamination studies do not have a worrying level of cyanotoxins; the data available in the literature cannot be used to reach any conclusion as to the microcystin production potential of Arthrospira spp. itself. Contamination by other cyanotoxin-producing cyanobacteria, however, is possible.
At least 12 different species of cyanobacteria have been proven to produce cyanotoxins. Some commercially available spirulina products have been found to contain additional cyanobacterial OTUs including a few known potentially toxic taxa.
Cyanobacteria tend to bind heavy metals from the environment, making it necessary to ensure the safety of cyanobacterial-derived products for pharmaceutical and nutritional applications. Experiments demonstrate that Spirulina platensis accumulates trace metals more effectively than Chlorella vulgaris — an advantage with regard to trace elements essential to humans but a liability if toxic metals are present.
Lead was detected in several products tested; arsenic and molybdenum were found in other products; in most cases, levels fell within the safety limits set by the European Food Safety Authority (EFSA).
There are potential hazards associated with the usual means of production of spirulina in open ponds; such systems are vulnerable to contamination with bacteria from animals, soil, and lake waters, including potential pathogens. A further cause of serious contamination in microalgal products may arise from the improper culture purity and the co-occurrence of potentially toxic cyanobacteria species such as Microcystis aeruginosa.
While the demand for spirulina dietary supplements continues to grow, product inspection in terms of authenticity and safety remains limited. There is limited understanding of nutritional composition across microalgal species, geographical regions, and seasons, all of which can substantially affect quality and safety value of products based on microalgae.
High-quality spirulina-derived products are necessary to ensure the best clinical safety and avoid contaminants.
Most herb-drug interactions identified in current sources are hypothetical, inferred from animal studies or cellular assays, or based on other indirect means; however, attention to this issue is needed for drugs with a narrow therapeutic index, such as cancer chemotherapeutic agents and warfarin. No specific well-characterized pharmacokinetic drug interactions with spirulina have been established in robust human clinical studies.
Health conditions that Cyanobacteria may help support.
Body systems that Cyanobacteria may help support.
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