Spirulina

1.1. Sources

'Spirulina' is a colloquial term used to refer to a blend of two bacteria, Arthospira Platensis and Arthospira Maxima. Sometimes these bacteria are called Spirulina Platensis and Spirulina Maxima, accordingly. The common name 'Spirulina' is derived from 'Spiral', which is in reference to its classical morphology being spiral shaped (although linear shaped Arthospira has been noted).^[1] Spirulina is also commonly called a 'blue-green' algae due to its color and its sources.

Nutritionally, Spirulina is technically a vegan source of complete protein^[2] that can be up to 70% protein by weight^[3] although some interventions use Spirulina with a 55% protein content.^[4][5] The amino acid composition of Spirulina is 'complete' (giving adequate amounts of all essential amino acids) but is relatively lower in cysteine, methionine, and lysine when compared to animal products.^[6][3]

Spirulina is a term used to refer to the two Arthospira bacteria that are non-toxic and eaten as protein-rich food products

1.2. Composition

Spirulina contains:

• Protein, which tends to fluctuate around 65-70% dry weight (at highest estimates)^[7]

• Of these proteins, the Phycobiliproteins (antenna-like proteins involved in light harvesting) named allophycocyanin, C-phycocyanin and phycoerythrin^[8] with phycocyanin comprising about half of Phycobiliprotein weight^[9] and Phycocyanin per se comprising up to 20% of Spirulina dry weight^[10][11]

• Phycocyanin is a holoprotein made up of smaller proteins, one of which is the bioactive phycocyaninbilin which may comprise between 0.6-1% of Spirulina by total weight.^[12]

• Braun lipoproteins, lipoproteins found in bacterial cell walls; may confer immunological benefits^[13]

• Some polypeptide structures such as polypeptide Y2^[14]

• Fatty acids such as γ-Linolenic acid (GLA) at up to 20.8mg/g (up to 25% of total fatty acids)^[15][16] Stearic Acid,^[17] Alpha Linoleic Acid, Palmitic Acid, and Linoleic Acid;^[7][18] exact composition varies depending on production.^[19] Total fatty acids tend to fluctuate around 6% by dry weight^[7]

• Heptadecane^[20]

• Carbohydrate, which tends to fluctuate around 14% of dry weight

• Of these carbohydrates, some immune system activating polysacchardes (Immulina) at 0.5-2% total dry weight (7-14% total carbohydrate)^[21] and Sodium Spirulin^[22]

• Trace minerals^[18] including Iron (50-150mg/100g), Calcium (600–1,200mg/100g), Magnesium (200-600mg/100g), and Selenium (50-200mcg/100g)^[23]

• Mostly pseudovitamin B12, or 7-adenyl cyanocobamide (87%) which is unable to be used by humans; a low and mostly irrelevant (13%) B12 content.^[24][25] For vegan B12 sources, Chlorella or Nori are more suitable

• β-carotene (pro-vitamin A)^[26] and some other carotenoids such as Zeaxanthin^[27] or 7-hydroxyretinoic acid and isomers^[28] with 200-400mg/100g total carotenoids^[23]

• Vitamin C (2-4mg/100g)^[23]

Spirulina is a protein-rich food product (approximately 55-70% dry weight), with a relatively low carbohydrate content of around 15% dry weight. It is a source of complete vegan protein. It also contains phycocyanin-containing phycobiliproteins which are thought to be some of spirulina's active ingredients. In addition, spirulina also contains several trace minerals, vitamins, and pro- and pseudo-vitamins.

1.3. Structure and Properties

The main active ingredient of Spirulina are commonly seen as the Phycocyanobilin proteins, with C-phycocyanin being the most commonly touted meta-component and consists of smaller protein components such as Phycocyanibilin. These structures resemble the body's endogenous bilirubin molecule. The bilin groups are also the source of the anti-oxidative effects of Phycocyanobilin proteins.^[29] Most anti-oxidant effects of Spirulina per se (excluding enzyme interactions in vivo) are due to the Phycocyanin component, as isolating different fragments and comparing them against each other on a weight basis shows that anti-oxidant potential of an extract correlates well with its Phycocyanin component.^[30]

Spirulina is 55-70% overall protein by total weight and split into three 'meta' proteins (allophycocyanin, C-phycocyanin and phycoerythrin). C-Phycocyanin is about 20% of the total weight and contains the main bioactive of phycocyanobilin, which is 1% of spirulina by total weight. Phycocyanobilin can be reduced to phycocyanorubin via the enzyme biliverdin reductase

Polysaccharides (not pictured) of the carbohydrate fragment and the carotenoids and gamma-linoleic acid may also be bioactive, but are seen as not the main bioactive

1.4. Gilbert's Syndrome

Gilbert's Syndrome (GS) is a familial hyperbilirubinemia (high serum bilirubin levels; greater than 17µmol/L)^[31] likely secondary to reduced activity of the enzyme bilirubin glucuronosyltransferase^[32][33] to around 25% of baseline activity.^[34] It is not the only form of hyperbilirubinemia, and is an autosomal recessive disorder^[31] affecting 3-12% of the population.^[33][35][36] GS is relevant as while it is a 'syndrome' it is seen as medically benign^[37] and elevated bilirubin appears to be protective against diseases of aging due to the antioxidant properties of bile acids^[38][39] while persons with GS are half as likely to die than normal controls (24 deaths per 10,000 person years in GS relative to 50 in control over a 9 year study periods);^[40] Spirulina is thought to mimic GS as both of them exert their antioxidant properties via inhibition of NADPH oxidase.^[41]

Of interest, when comparing persons with GS relative to controls at baseline (prior to the 9 year study period) those with GS had significantly lower BMIs (4.3% less than control), less risk for cardiovascular diseases (43%), diabetes, and mental illness (11.6% relative to 24.2%).^[40]

Gilbert's Syndrome (GS) is a genetic condition characterized by higher than average bilirubin levels, but, possibly due to the antioxidant properties of bilirubin, the syndrome is associated with health benefits and lower rates of death. Spirulina inhibits the same enzyme that bilirubin does to exert antioxidant effects, and it is hypothesized that Gilbert's Syndrome would have similar benefits to supplemental spirulina

2.1. Mineral Detoxification

Cyanobacteria tends to be an accumulator (biosorbent) of heavy minerals ex vivo^[42][43][44] due to ion-exchange binding^[45] and when applied directly to tissues with heavy metal accumulation can significantly reduce heavy metal toxicity (100mcg of spirulina hexane extract removing 89.7% of arsenic^[46] which has been noted elsewhere^[47]); bioactives in the hexane extract appear more potent than the alcoholic extract.^[46][47]

Spirulina (250-500mg/kg) has shown efficacy in preventing mineral toxicity form occurring in pregnant rats' offsprings when the mothers were given fluoride^[48] and has been noted to reduce lead accumulation in the neural tissue of rat pups from 753-828% of baseline (lead group) to 379-421% with 2% Spirulina in the diet (relative to no lead group).^[49] Protective effects in pregnant rats on their pups have been noted with cadmium as well.^[50]

In male rats, 300mg/kg can attenuate mercury accumulation in the testes (which is thought to partially contribute to antioxidative effects)^[51] and protection against mercury has been noted elsewhere in kidneys (800mg/kg spirulina in mice).^[52] The other species of cyanobacteria known as spirulina fusiformis (also a source of C-Phycocyanin^[53]) appears to also possess testicular protective effects against mercury^[54] and to reduce serum biomarkers of mercury toxicity^[55] (similar to spirulina itself^[56])

Spirulina is one of the few molecules in existence that has a body of evidence to support 'detoxifying' actions as it pertains to heavy metals, and has demonstrated this efficacy in animal models against a wide variety of minerals, including cadmium and mercury, and has been shown to be safe for pregnant rats in order to reduce the effects of mineral toxicity on rat pups

Relative to other agents, spirulina (2% of the diet) is approximately twice as effective as 5% dandelion extract in reducing lead accumulation in rat pups^[49] and when 300mg/kg spirulina is compared against 400mg/kg Panax ginseng in cadmium induced testicular toxicity the effects are comparable on all accounts except spirulina increasing superoxide dismutase to a greater level^[57] and seems somewhat comparable to an equal dose of Liv-52 (Ayurveda combination formula) at reducing both cadmium^[58] and lead^[59] toxic effects, although they were not additive.^[58][59]

Relative to other agents that may reduce the biochemical harms of excess heavy metals, spirulina appears to be either greater or comparable to the other drugs

One blinded intervention has been conducted where Spirulina (250mg) paired with Zinc at 2mg was able to reduce arsenic levels in the body after persons were exposed to arsenic via drinking water.^[60] Persons living in India and who were consuming arsenic via drinking water installed a filter and then were divided into placebo or Spirulina after two weeks for 14 weeks, urinary arsenic levels at baseline were 72.1+/-14.5, and 78.4+/-19.1μg/L for placebo and Spirulina respectively, decreased 72.4-74.5% after the filters in both groups, and increased to 138+/-43.6 μg/L in the Spirulina group after 4 weeks. Hair arsenic levels were 3.08+/-1.29 and 3.27+/-1.16 μg/g at baseline, and decreased 3% in placebo and 47.1% in Spirulina.^[60] 

These mineral detoxifying effects have been confirmed in humans once, as pertaining to arsenic

2.2. Phase I Enzyme Interactions

Oral administration of spirulina to rats over the course of five weeks appears to be able to suppress CYP2C6 enzymatic activity in a manner that is not associated with a reduction in mRNA nor protein levels.^[61] CYP1A2 and CYP2E1 are also downregulated, but this is associated with reductions in mRNA and protein levels.^[61]

Spirulina over five weeks to rats also appears to upregulate the mRNA expression and protein content (as well as overall activity) of the CYP2B1 and CYP3A1 enzymes.^[61]

Spirulina appears to be capable of modifying a few proteins in phase I metabolism

2.3. Drug-Drug Interactions

The proteinaceous C-Phycocyanin appears to be able to inhibit the MultiDrug Resistance Receptor 1 (MDR1) in human hepatocellular carcinoma cells. Although this one study noted an IC₅₀ of 50uM for C-Phycocyanin and 5uM for Doxorubicin, while in the presence of 25uM C-Phycocyanin the IC₅₀ of Doxorubicin was improved five-fold to 1uM and overall proliferation reduced further.^[62] C-Phycocyanin appeared to enter the cell (seen via fluorescence) and inhibit MDR1 at the transcriptional and translational level, which increased cellular accumulation of Doxorubicin and reduced both mRNA and protein content of MDR1.^[62] The mechanisms appears to be mixed via COX-2 inhibition, as it reduced PGE2 levels (which increase MDR1) which may be secondary to reducing NF-kB and AP-1 activity via NAPDH oxidase inhibition (anti-oxidant effects)^[62] and has been reported elsewhere in non-carcinogenic tissue^[63] and regular macrophages treated with the pro-oxidant 2-acetylaminofluorene.^[64]

Other studies looking at the combination of Doxorubicin and C-phycocyanin note that the latter can prevent cardiotoxicity from the former without inhibiting its apoptotic effects on ovarian cancer cells.^[65]

Spirulina may aid the kinetics of some anti-cancer drugs by mixed anti-oxidant and anti-inflammatory mechanisms, as oxidation tends to increase the amount of the MDR1 receptor, which 'boots' drugs from the cell and phycocyanin prevents this ejection

3.1. Mechanisms

Spirulina appears to be an NADPH complex inhibitor similar to bilirubin (the catabolite of heme which is an endogenous NADPH inhibitor; Phycocyanobilin from Spirulina has a similar structure^[66] and is reduced to phycocyanorubin via the same enzyme (biliverdin reductase^[67]). Beyond inhibition, spirulina has been implicated in reducing the expression of the NADPH complex (22-34% reduction in the expression of the p22phox subunit of NADPH oxidase^[68]).

Spirulina's main mechanisms of action as an NADPH oxidase inhibitor and suppressor appears to have roles in neurology

A doubling of the CX3C chemokine receptor 1 (several names including fractalkine, CX3CR1, and GPR13) has been noted to be doubled in the microglia of rats relative to placebo.^[69] It is thought this may play a role as, when the receptor is activated, less synthesis of proinflammatory cytokines (IL-1β and TNF-α) occurs^[70] and this has also been shown to reduce microglia activation and reduce pathology of Parkinson's disease.^[71]

Spirulina may increase the activity of the CX3CR1 receptor, and this appears to occur as a per se mechanism and may be independent of NADPH oxidase inhibition

3.2. Neuroprotection and Cognitive Decline

Oral doses of 100mg/kg C-Phycocyanin to rats has been associated with acute protection against kainate-induced neurotoxicity in the rat hippocampus, significantly reducing microglia and astrocyte activation when measured a week after kainate injections.^[72] These observed results may be secondary to kainate-induced toxicity being mediated through the pro-oxidative NADPH oxidase activation and membrane translocation^[73] and the C-Phycocyanin component Phycocyanobilin inhibiting activation of this complex.^[74]

Spirulina appears to be neuroprotective against excitotoxicity, possibly secondary to NADPH oxidase inhibition

Neuroprotection has also been observed in response to MPTP injections (a toxin mimicking Parkinson's Disease), where 150-200mg/kg oral Spirulina significantly attenuated dopaminergic losses in response to the toxin^[75] and a similar dopaminergic toxin (6-ODHA or 6-hydroxydopamine) also appears to have its neurotoxicity reduced following 28 days of 0.1% spirulina in the diet, which outperformed 2% blueberries (anthocyanin source) for protecting from neurodegeneration in the injection site when measured at 1 week post injection (opposite trend at 4 weeks).^[76]

Toxic responses to MPTP also appear to be mediated via NADPH complex activation^[77][78][79] as does the toxic response to 6-hydroxydopamine,^[80] although induction of fractalkine does also confer protective effects against 6-hydroxydopamine.^[71]

In regards to dopaminergic (dopamine related) toxins, spirulina appears to be highly protective following oral ingestion of reasonable dosages by dual mechanisms (fractalkine induction and NADPH oxidase inhibition). Spirulina appears to be very promising for reducing the risk of developing Parkinson's Disease due to these effects

Haloperidol-induced symptoms of tardive dyskinesia in rats are also reduced with 180mg/kg spirulina daily alongside continued haloperidol injections, and doses as low as 45mg/kg when injections were ceased prior to spirulina ingestion.^[81] Haloperidol has also been noted to work via excessive oxidation^[82] that is produced from NADPH oxidase activation^[83] and thus is tied into the main mechanism of spirulina.

Haloperidol toxicity is also protected against from spirulina due to NADPH oxidase inhibition

Spirulina at 45-180mg/kg oral intake for one week prior to ischemia/reperfusion (experimental stroke) is able to exert dose-dependent protective effects with the higher dose halving infarct size and fully normalizing parameters of lipid peroxidation and antioxidant enzymes. ^[84] These protective effects have been noted elsewhere with spirulina at 0.33% of the diet where it was more protective than the reference drug (2% blueberries as source of anthocyanins)^[85] and 200mg/kg of isolated C-Phycocyanin for one week in gerbils prior to ischemia/reperfusion has also confirmed absolute reduction of lipid peroxidation and reduced infarct size to 4.3% of ischemic control (50mg/kg was able to reduce infarct size to 17.2% of control, also being highly effective) and normalized the neurological score after surgery when measured 24 hours later.^[86]

Spirulina is able to exert protection against strokes, with 200mg/kg of isolated C-phycocyanin conferring almost absolute protection from stroke. These remarkable protective effects need to be replicated in higher mammals to draw conclusions but are incredibly promising

Iron neurotoxicity (via pro-oxidation) has also been demonstrated to be attenuated with Spirulina's C-Phycocyanin component in a SH-SY5Y neuroblastoma cell line, and using LDH leakage as indicator of cellular death Phycocyanin was able to reduce cell death from 69.10+/-2.14% in Iron-control to 28.70+/-2.56% at 500ug/mL.^[87] 1000mcg/mL Spirulina (very high concentration) was demonstrated to per se induce cytotoxicity in this study.^[87] This mechanism may not be related to NADPH oxidase inhibition, as spirulina is known to be a mineral chelator.

Spirulina appears to have neuroprotective effects against mineral toxicity, which may not be related to NADPH oxidase inhibition as spirulina is an effective mineral chelator (see the Pharmacology section and Mineral Detoxification)

Due to the above neuroprotective properties tied into NADPH, it is hypothesized that this enzyme plays a central role in inflammatory and oxidative neurodegenerative diseases.^[12]

Spirulina has been found to nonsignificantly increase neuronal density (indicative of neurogenesis) at 0.1% of the diet despite being infected with α-synuclein,^[69] a component of the protein aggregates seen in Alzheimer's and Parkinson's disease and sometimes used as a research toxin when injected.^[88] The protection (assessed by TH and NeuN immunostaining) appeared to be significant in the substantia nigra,^[69] an area of the brain where neurodegeneration is thought to be causative of Parkinson's.^[89][90] Spirulina has also been investigated ex vivo for blocking the synthesis of beta-amyloid protein aggregates, and spirulina (EC₅₀ of 3.76mcg/mL) outperformed all other tested food extracts including ginger (36.8mcg/mL), cinnamon (47.9mcg/mL), blueberries (160.6mcg/mL) and turmeric (168mcg/mL, diluted source of curcumin)^[91] but underperformed relative to some isolated molecules such as 1,2,3,4,6-penta-O-galloyl-b-D-glucopyranose(PGG) from Paeonia suffruticosa (2.7nM), EGCG (green tea catechins) at 10.9nM, resveratrol at 40.6nM, and S-diclofenac at 10nM as comparator.^[91]

One study has noted that β-amyloid pigmentation (in aged but not diseased rats of the SAMP8 line) was restored to levels similar to the non-aged mouse with 50-200mg/kg, with 200mg/kg being more effective at reducing lipid peroxidation and improving catalase activity.^[92]

It is thought that microglia activation is the mechanism, as via OX-6 staining there is a reduction in microglia activation with spirulina^[69] which is known to be a mechanism of α-synuclein induced neurotoxicity^[93] and is dependent on NADPH oxidase activation.^[94] This prevention of microglia activation has been traced back to the phycocyanobilin components in vitro^[95] and reaches near absolute levels at 400mg/kg in rats (estimated human dose of 64mg/kg).^[96]

Spirulina appears to have mechanisms to prevent accumulation of beta-amyloid pigmentation and alpha-synuclein (noted ex vivo) and is able to prevent these proteins from inducing inflammatory and neurotoxic effects (confirmed in rats following oral ingestion). Due to this, spirulina may have use as both therapy and prevention for Alzheimer's and Parkinson's, which requires further human evidence, but is very promising based on the animal evidence

Spirulina at low intake (5mg in rats) has been noted to attenuate the age-related increase of TNF-α^[97] and in normalizing the age-related decline in memory function as assessed by the accelerated aging mouse line of SAMP8, where activity and body weight following 50-200mg/kg was normalized with the regular mouse control.^[92]

The reduced rate of neurodegeneration may also apply to healthy cognitive aging, and due to less neurodegeneration, continual usage of spirulina may improve cognition in older people

3.3. Neurogenesis

Spirulina, in the diet at 0.1% in rats, appears to protect stem cells in the brain from having their proliferation reduced by inflammation (as assessed by LPS injections, likely related to Fractalkine induction or NADPH oxidase inhibition) and was shown in vitro to enhance stem cell proliferation at 0.62ng/mL and 125ng/mL.^[98] The promotion of stem cell neurogenesis appears to be secondary to reducing the suppressive effects of TNF-α on proliferation, possible via Fractalkine induction.^[98]

Other studies noting neuronal density over time may note some increases, including a non-significant trend to increase with 0.1% Spirulina in the diet for 4 months (rats) despite neurotoxic α-synuclein infection (in NeuN stained cells, loss was seen with TH staining).^[69]

Limited evidence suggests that spirulina can promote regeneration of neurons via stem cells, which is secondary to reducing inflammation in the brain (which preserves normal regeneration rates) and has been demonstrated to occur in vivo at 0.1% of the rat diet (a very feasible human dose)

3.4. Motor Neurons

The reduced rate of neurodegeneration seen from spirulina (secondary to suppressing glial cell activation in response to toxic stressors) has been noted to improve motor function as assessed by sciatic function index (400mg/kg outperforming 800mg/kg in rats)^[96] and another study using the mouse model of Amyotrophic lateral sclerosis (ALS; the mouse model is the SOD1 mouse line) noted that 10 weeks of 0.1% spirulina was able to greatly attenuate the rate of motor neuron decay when compared to control.^[99] These results have been stated to be preliminary and requiring replication.^[100] 

The reduced rate of neurodegeneration may apply to motor neurons as well, which would promote function and muscular control during aging and disease processes (and may also underlie the effects on power output that have been noted with spirulina). This claim requires more evidence, however

3.5. Depression

At least one study has been conducted with spirulina in a Forced Swim Test in rats, although this study used spirulina hydrolyzed by malted barley in one group.^[101] Spirulina and Hydrolyzed spirulina were both significantly more effective than control at the anti-depressive model of the Forced Swim Test, but the control drug of 10mg/kg fluoxetine grealty outperformed Spirulina.^[101]

Preliminary evidence suggests that spirulina could have anti-depressant actions, but they appear to be quite weak

4.1. Absorption

Spirulina has greater bile acid binding properties than casein (comparator) and appears to reduce cholesterol solubility in micelles.^[102] Ex vivo, the uptake of cholesterol into Caco-2 cells appears to be reduced with spirulina, and ingestion of 10% spirulina in the diet for 10 days in rats fed a high cholesterol diet did not alter liver cholesterol but increased fecal cholesterol excretion by 20.8-23%.^[102]

Spirulina appears to increase the amount of cholesterol defecated out, which is secondary to preventing its absorption in the intestines. It appears to be a moderate degree of potency, not overly remarkable, but still greater than many other supplement options

A study in young and otherwise healthy persons has noted that the postprandial spike in triglycerides following ingestion of a high fat meal is attenuated when eaten alongside 5g spirulina (up to 42% at 4.5 hours after the meal).^[103] This reduction in triglycerides appeared to affect youth more than older persons, with a 30% reduction in AUC seen in persons aged 10-12yrs while those above 13 years of age did not note any benefit.^[103]

There appear to be mechanisms for triglyceride absorption inhibition, but these are oddly age-dependent and the preliminary evidence suggests that they might be unreliable.

4.2. Lipoproteins and Triglycerides

Animal models note that 0.33g/kg spirulina for 30 days in a rat model of fructose-induced metabolic syndrome is able to reduce LDL-C (79%), total cholesterol (33-36%), and vLDL-C (23%) while increasing HDL-C (55%) and still appeared to be effective when the fructose insult was not stopped, although the benefits were attenuated to 39% (LDL-C), 28% (vLDL-C), and 43% (HDL-C);^[104] relative to the comparator (Metformin at 500mg/kg), spirulina nonsignificantly underperformed.^[104] These benefits have also been noted in otherwise healthy mice fed a high cholesterol diet, with 10 days of supplementation increasing HDL-C by 26% while LDL-C plus vLDL-C was reduced (21%) and total cholesterol unchanged^[102] and longer supplementation (5% of the diet in type I diabetic mice for 30 days) has been noted to normalize LDL-C and HDL-C.^[105] It is thought that these improvements in lipoproteins are secondary to the liver (hence using fructose obesity as a research model)^[104] and as such the benefits of spirulina appear to be additive with physical training.^[106]

The aforementioned fructose study also noted a reduction in triglycerides by 39-51% (reduced to 28-34% with continued drinking of fructose) which was similar to Metformin (43%)^[104] but has been noted to not be augmented by physical exercise.^[106] One study has suggested that the reduction in LDL-C is dependent on triglycerides, but that HDL-C was independent^[107] although another notes the opposite.^[108]

In research animals, spirulina appears to very effectively reduce vLDL and LDL cholesterol (sometimes seen as bad) and quite potently increase HDL-C with pretty strong effects on triglycerides as well. Although the preliminary research at this moment in time suggests that it is as potent as Metformin, these effects may be dependent on fixing a fatty liver

For human studies, one using 8g spirulina for four months (otherwise healthy korean subjects aged 60-87yrs) noted that cholesterol and LDL-C were reduced by 7.9% and 11.5% in females but all cardiometabolic parameters in men (as well as HDL-C and triglycerides) were not significantly affected, although there was an increase in superoxide dismutase activity and IL-2 and reduction of TBARS.^[5] Another study in older persons with hypercholesterolemia (40-60yrs with 4g spirulina for three months) noted a halving of LDL-C with a small but significant increase in HDL-C^[109] and a lower dose (1g spirulina daily for 12 weeks) in dyslipidemic patients reported reductions in triglycerides (16.3%), LDL-C (10.1%), and total cholesterol (8.9%) with a nonsignificant trend to increase HDL-C (3.5%).^[110]

Other studies include one using an open-label design and otherwise healthy adults noted a 15% increase in HDL-C with 4,500mg spirulina for six weeks while total cholesterol and LDL-C decreased (16.6% and 10%) with a reduction in triglycerides (24%)^[108] and a study in healthy active youth (5g for 15 days) has noted a reduction in fasting triglycerides (20.2%) independent of changes in total cholesterol and HDL-C.^[103] One other study notes 'beneficial changes' without giving the data required to quantify.^[107]

1,000mg spirulina for one month in youth with nephrotic syndrome (kidney disorder characterized with an increase in blood lipids^[111]) noted reductions in total cholesterol (35.5%), LDL-C (41.9%), vLDL-C (29.7%), triglycerides (29.7%) and a nonsignificant decrease in HDL-C (14.8%; the ratio was beneficially altered, however).^[112]

Spirulina appears to improve the lipoprotein profile in humans, following standard supplemental doses, and although the evidence is not vast enough to come to a conclusion, it does appear that spirulina is quite potent at improving cardiometabolic risk factors when baseline stats are not desirable (ie. in diseased people)

4.3. Cardiac Tissue

C-Phycocyanin form the protein fragment of Spirulina, at a concentration of for up to 48 hours, noted that cardiomyocyte death induced by doxorubicin was reduced with C-Phycocyanin at 10ug/mL in isolation being more effective than Spirulina at five-fold the concentration (50ug/mL), and was thought to be secondary to reducing Doxorubicin-induced oxidation and subsequent mitochondrial damage.^[65] Interestingly, the anti-tumor activities of Doxorubisin (in ovarian cancer cells) was not inhibited by the same concentrations of C-phycocyanin and Spirulina^[65] and these results suggesting lack of inhibition have been replicated elsewhere.^[113]

These protective effects have been noted in vivo in rats fed Spirulina at 250mg/kg bodyweight (moderate dose), where mortality from Doxorubisin reached 53% in control and was reduced to 26% with Spirulina.^[113]

Another indirect mechanism of cardioprotection may be through Spirulina's anti-oxidant effects, as the anti-oxidant effects of Phycocyanin have been implicated in reducing superoxide radical formation in cardiac tissue by 46-76% in rodents fed a Spirulina enriched water extract.^[68]

Spirulina may be cardioprotective, in terms of the heart tissue itself

4.4. Platelets

Spirulina appears to inhibit platelet aggregation via its C-Phycocyanin component, as concentrations of 0.5-1nM (very low) appear to inhibit aggregation induced by collagen and U46619 with an IC₅₀ value of 4 and 7.5nM; this lower dose was ineffective at potently inhibiting thrombin and arachidonic acid induced clotting, but a higher concentration of 2uM was able to inhibit aggregation by these two agents by 78% and 92%, respectively.^[114] A later study suggested the IC₅₀ value of AA-induced aggregation was 10ug/mL,^[115] and all inhibition appeared to be reversible, and the mechanisms appears to be mediated via preventing Ca²⁺ release in platelets^[114] and possibly related to preventing thromboxane A2 formation.^[115]

4.5. Blood Pressure and Flow

Mechanistically, Spirulina appears to possess anti-hypertensive peptides in the protein fragment that inhibit the ACE enzyme. In Spirulina, this peptide is a chain of Isoleucine-Glycine-Proline (Ile-Gly-Pro) and dubbed IQP.^[116] IQP possess an IC₅₀ of 5.77 ± 0.09 μmol/L and is a noncompetitive inhibitor,^[117] and either injections of 10mg/kg acutely^[117] or week-long treatment with 10mg/kg in rats with this peptide in isolation appears to be not significantly different than an equal dose (10mg/kg) captopril, an ACE inhibiting drug.^[116]

A study conducted in obese rats with 5% of the diet as spirulina noted that, when induced by phenylephrine (to induce hypertension) that blood vessels were more relaxed than control rats.^[107] These benefits appear to exist for fructose-induced obesity (which hyperrespond to phenylephrine induced constriction) and vasomotor reactivity is reduced to levels of lean controls^[118] and this was later replicated with a raw ethanolic extract of Spirulina.^[119] A later study investigating mechanisms noted a concentration-dependent increase with Spirulina's effects, where contraction of the aortic rings with endothelium was 23.88+/-6.6% of its normal amount with 1mg/mL Spirulina when measured in vitro and without endothelium it was reduced to 67.14+/-15.45%.^[120] Incubation with Indomethacin (selective COX1 inhibitor) and L-NAME again reduced the ability of Spirulina to prevent constriction of the aortic ring,^[120] and the authors concluded that Spirulina enhanced either the production or release of NO from the endothelium of phenylephrine-induced aortic rings.^[120]

This appears to be mediated by cyclooxygenase (COX1 in particular), as inhibition with indomethacin abolished the effect; although nitric oxide release was implicated in part with Spirulina.^[107]

In rats, spirulina appears to reliably decrease blood pressure, possibly via its ACE inhibitory peptides, but other mechanisms appear to be at play that reduce the contractility of the blood vessels

In humans, a decrease in blood pressure has been observed after 4 weeks of treatment with 4.5g Spirulina; this study was not catered for persons with hypertension, but it appears many of the subjects fell into hypertensive categories at baseline; exact measurements not given.^[107]

5.1. Mechanisms

Possible mechanisms for the interactions between Spirulina and glucose metabolism as via components acting as an NAPDH oxidase complex inhibitor,^[67] where NAPDH oxidase mediates lipotoxicity of pancreatic beta-cells (that secrete insulin).^[41] 

Secondary to inhibiting NADPH, which links toxin responses to pancreatic β-cell destruction, spirulina is thought to be able to prevent toxin-induced destruction of β-cells, which is involved in the etiology of diabetes

5.2. Diabetes Risk

Spirulina (10mg/kg) over 30 days is able to reduce blood glucose that is elevated by alloxan (a β-cell toxin) from 250mg/dL to 160.45mg/dL (64% of baseline, 183% of control)^[121] and preloading isolated phycocyanin (100-200mg/kg) for 2 weeks prior to and 4 weeks after alloxan was able to statistically normalize blood glucose (at day 28, seemed to be less effective one week after alloxan injection).^[122]

Other studies have noted that an average of 0.33g/kg spirulina daily to fructose-fed rats for 30 days was able to reduce the subsequent blood glucose by 54-60% (no dose-response noted) which was equally potent as Metformin at 500mg/kg (46%).^[104] KKAy mice (genetically obese, hyperglycemic, and insulin resistant^[123]) given 100mg/kg phycocyanin for 3 weeks and then given an oral glucose tolerance test noted a 51% reduction in the glucose spike after phycocyanin treatment; fasting blood glucose was also reduced and insulin sensitivity improved, and phycocyanin outperformed the reference drug of 2mg/kg pioglitazone.^[124]

In diabetic models (toxin induced, diet induced, and genetically induced) spirulina appears to be highly protective and rehabilitative

Some rat evidence suggests a reduction of blood glucose in otherwise healthy rats (87.56 to 74.80 mg/dL; 14.6% reduction) associated with an increase in serum insulin^[121] although other studies have failed to note such a decrease.^[122]

There is mixed animal evidence to assess whether or not spirulina influences blood glucose in otherwise healthy subjects

5.3. Insulin Resistance

A study in 25 persons with type II diabetes 67.2+/-11.5yrs old with 2g Spirulina daily for 2 months while maintaining regular diets and exercise regimens noted that fasting blood glucose decreased to 88% of baseline while control had no changes, and postprandial glucose decreased to 92% of baseline.^[125] While HbA1c remained static at 8.7+/-1.5 in control, it decreased from 9.0 to 8.0 after 2 months of 2g Spirulina ingestion; this study also noted a modest 1.4% increase in HDL-C and a 13% reduction in triglycerides with nonsignificant trends to improve LDL-C and vLDL-C.^[125]

Spirulina has also shown promise as adjunct therapy. HIV is associated with insulin resistance (and other abnormalities) due to highly active antiretroviral therapy (HAART),^[126] and at least one study has been conducted to see if Spirulina would be good adjunct therapy to reduce insulin resistance.^[127] In these persons with insulin resistance, 19g of Spirulina (powder) over 2 months was associated with an increased rate of glucose diposition (−2.63%/min relative to control's −1.68%/min) and the improvement in insulin sensitivity was measured at 224.7% in Spirulina and 60% in control, and these benefits appeared to affect all subjects with no non-response.^[127] This study noted less adherence to the Spirulina treatment due to the taste, which was not masked and reduced pill consumption to 65% of given pills.^[127] This study ultimately concluded that Spirulina, relative to soy beans (control) had a 1.45 greater chance of improving insulin sensitivity.

Both studies note improvements in glycemic profiles, although one measured fasting blood glucose and HbA1c while the other measured insulin sensitivity

5.4. Adjunct Therapy

At least one animal study has suggested that rosiglitazone-induced bone losses (observed in humans in observational studies^[128]) can be attenuated with coingestion of Spirulina, where 500mg/kg bodyweight Spirulina alongside 10mg/kg bodyweight Rosiglitazone nonsignificnatly outperformed Rosiglitazone alone on reducing blood sugar and body weight, and attenuated bone losses although it could not outright prevent.^[129] Spirulina in isolation was about half as effective as rosiglitazone in reducing blood sugar.^[129]

6.1. Mechanisms

In a mouse model of metabolic syndrome, spirulina has been noted to reduce adipose tissue macrophage infiltration^[130] (macrophages in visceral fat tend to deposit themselves and secrete inflammatory cytokines^[131] which may exacerbate symptoms of metabolic syndrome^[132]) which appears to be a consequence of NADPH oxidase inhibition.^[132]

Secondary to NADPH oxidase inhibition and suppressing macrophage accumulation in body fat, spirulina may play a role in augmenting fat loss in people with metabolic syndrome. This mechanism is rehabilitative, and would serve no purpose in an otherwise healthy individual

6.2. Interventions

100mg/kg Phycocyanin has been noted to reduce body weight in KKAy mice (genetically obese, hyperglycemic, and insulin resistant^[123]) associated with a reduction in food consumption over 21 days.^[124] This has been noted elsewhere where the weight reducing effects of spirulina (in mice with metabolic syndrome) was reduced 7.1% relative to metabolic syndrome control (but still 41% heavier than healthy control).^[130]

In genetically obese rodents, spirulina does appear to be able to exert anti-obese effects to a small degree. It does not appear to be overly potent on this parameter

7.1. Mechanisms

Braun lipoproteins, lipoproteins found in bacterial cell walls, may mediate aspects of the immunological aspects of Spirulina. One study found the modified amino acid 2,3-dihydroxypropylcysteine via HPLC indicative of the presence of Braun proteins,^[13] while the mechanisms of Spirulina-mediated immune potentiation appear to be mediated through TLR2 receptors, of which lipoproteins are agonists of;^[133] giving biological plausibility. TLR2 was found to mediate the effects of Spirulina as cells expressed TLR2 showed NF-kB activation in response to Spirulina and those expressing MD-2 and TLR4 failed to do so, although this study attributed the observed effects to polysaccharides.^[134]

Inhibition of NF-kB has been noted elsewhere in both macrophages and splenocytes at 100μg/mL of the lipid extract.^[135]

The polysaccharide components are also known to activate the immune system (similar to polysaccharides from Panax Ginseng and Ganoderma Lucidum), this polysaccharide has been named Immulina or Immolina,^[21] which may draw confusion as this is also a patented name for a Spirulina product.^[13][136] This polysaccharide, at concentrations between 1ng/mL to 100ug/mL, increased the mRNA levels of various tested chemokines (IL-8, MCP-1, MIP-1a, IP-10), and doses as low as 1ng/mL induced mRNA of TNF-α and 100ng/mL to induce IL-1β; the induction of these mRNAs was lesser than LPS, and Immolina did not influence cell viability or differentiation.^[137]

Some mechanisms related to the immune system are due to compounds acting as ligands to immune cell receptors and activating these cells. The low concentrations needed suggest that these mechanisms are active in vivo

Conversely to the pro-inflammatory aspects above, the biliprotein C-Phycocyanin acts as a selective COX-2 inhibitor (which is associated to some of its benefits against colon cancer^[138][139]) and incubation with activated macrophages (via LPS) with C-phycocyanin can result in macrophage apoptosis via COX-2 inhibition (which is induced by LPS).^[140] The inhibitory potential of C-phycocyanin is potent with an IC₅₀ value of 180nM,^[141] and it can technically inhibit COX-1 as well but the IC₅₀ value is higher at 4.47uM, and has the ratio of COX1/COX2 inhibition is 0.04 and thus selective.^[141] On a molar basis, C-phycocyanin was more inhibitory of COX2 than celecoxib (IC₅₀ 260nM) and Refecoxib (IC₅₀ 400nM) although the latter two drugs were more selective (0.015 and lesser than 0.0013).^[141] The inhibitory potential of Phycocyanin is reduced to 9.7uM when the molecule itself is reduced (after accepting electrons, its anti-oxidant mechanism).^[141]

Secondary to COX-2 inhibition and possibly other anti-inflammatory actions (iNOS inhibition), 20-50mg/kg injections of Phycocyanin appears to significantly and acutely (one injection) reduce circulating chemokines such as PGE2 and TNF-α that are stimulated in response to pro-inflammatory stimuli, and pain-relieving effects are also observed (but 50mg/kg Phycocyanin is outperformed slightly by Ibuprofen at the same dose).^[142]

Despite these predominately anti-inflammatory (and possibly immunosuppressant) activites noted above, isolated Phycocyanin has been noted to enhance adaptive immunity in mice. This study noted that oral ingestion of Spirulina for 6 weeks was able to, after mice were primed with the antigen (molecule that adaptive immunity 'locks on' to) that an increased amount of total and antigen-specific Immunoglobulin A (IgA) while suppressing allergenic IgE secretion.^[143]

The anti-oxidant effects of NADPH oxidase inhibition (seen mostly in the neurology section and liver section) also appear to influence anti-inflammatory effects because of the selective COX-2 inhibitor compound

7.2. Natural Killer Cells

Two pilot studies (unblinded) using Spirulina at 400mg daily (but with a higher concentration of Braun lipoproteins, those found in gram-negative bacteria cell walls) noted that Natural Killer (NK) cell activity increased by 40% as assessed by tumor killing ability (one study) and mRNA production of NK cells increased by 37-55% (200mg and 400mg, respectively) after a week of supplementation; this study did recieve a grant from the company supplying the Spirulina, however.^[13] Enhanced NK cell cytotoxicity (function) has been noted elsewhere with a Spirulina hot water extract.^[144]

A handful of studies on the subject do suggest that spirulina can increase natural killer (NK) cell activity in the body after a relatively low-dose ingestion

In animals, the increase in NK cell activity appears to be mediated via Myeloid differentiation primary response gene (MyD88) which is in the TLR4 activation pathway, as abolishing this protein abolishes the NK activation seen with Spirulina.^[145] Spirulina was also synergistic with a MyD88 inducer in this study, despite the inducer not having any ability to boost NK activity per se, and this study noted that with 0.1% Spirulina hot water extract added to food that NK activity increased in 2 weeks.^[145]

The induction of NK cell activity may be non-selective mediated via toll-like receptors, as abolishment of either TLR2 or TLR4 does not diminish the NK enhancing activity of Spirulina but double-abolishment does.^[145] Although TLR3-TICAM-1 can induce natural killer cell activation,^[146] TICAM-1^-/- mice do not appear to reduce the efficacy of Spirulina.^[145]

Spirulina appears to work via a TLR2/4 pathway that is dependent on MyD88

7.3. Neutrophils

Some studies measure serum Myeloperoxidase (MPO) as a biomarker of Neutrophil activation, and find dose-dependent reductions in serum MPO with near abolishment of oxidative stress-induced MPO increases at 6g/kg Spirulina in rats.^[147]

Lower doses (25-100mg/kg) are associated with significantly attenuated MPO induction (by alloxan), but not abolishment.^[148]

7.4. Arthritis

200mg/kg and 400mg/kg Spirulina daily to rats injected with collagen (to induce arthritis) and then fed Spirulina over the course of 45 days showed normalized joint histopathology (visual inspection under microscope) and normalized biochemical markers such as lipid peroxidation.^[149] The rats fed 400mg/kg, after visual inspection, appeared to be not significantly different than control rats while 200mg/kg still possessed some visual arthritic symptoms.^[149] This higher dose has also been associated with normalizing motor function in response to collagen injections, although this mechanism was thought to be secondary to suppressing glial cell activation (an anti-inflammatory effect).^[96]

This anti-arthritic effect has been noted elsewhere with 800mg/kg oral intake Spirulina (chosen as preliminary testing suggested it was more potent than 200, 400, and 600mg/kg) noted that Spirulina was able to reverse the pro-arthritic trend of a test drug in as little was a week^[150] and acted to almost completely normalize β-Glucuronidase and β-galactosidase in the liver, spleen, and plasma to control levels which not changing these parameters in a Spirulina fed control.^[150] Another study using a zymosin-induced arthritic model using 100 and 400mg/kg Spirulina orally noted that the expected increase in β-Glucuronidase was inhibited 78.7% and 89.2%, respectively. When using 10mg/kg Triamcinolone as a reference drug, it inhibited 94.1% and was seen as nonsignificantly more potent than 400mg/kg Spirulina.^[151] Protective effects were seen via histology, with 400mg/kg outperforming 100mg/kg and the reference drug being most effective.^[151]

Preliminary evidence in animals suggests that spirulina is a potent anti-arthritic agent, and at least two studies suggest that toxin-induced arthritis is almost normalized in lab rats. It appears to be of similar or slightly lesser potency than Triamcinolone (pharmaceutical corticosteroid)

7.5. Allergies

2g of Spirulina for half a year (6 months) in adults (30.1+/-6.69) with allergic rhinitus (nasal allergies) was associated with a highly significant improvement in subjective symptoms such as reduced frequency of nasal discharge, nasal congestion, and nasal itching and sneezing.^[152] On a rating scale of 1-10 with how satisfied participants were with the treatment, spirulina rated on average 7.21+/-1.01 (how satisfied) and 7.44+/-0.89 (how effective) while placebo rated 3.40+/-1.71 and 3.54+/-1.37, respectively.^[152] Similar beneficial results have been reported elsewhere, where 1-2g of Spirulina over 12 weeks noted that immune cells isolated from the persons ingesting 2g daily had suppressed secretion of the pro-inflammatory cytokine IL-4 in response to an antigen.^[153]

7.6. Interventions

One study on elderly (60-87yrs; n=78) noted that 8g of Spirulina daily for 16 weeks (4 months) was associated with an increase in IL-2 (144% in men, 146% in females) and alterations in IL-6 (down to 73.4% of control in men, up to 176% in females), the altered ratio being seen as anti-inflammatory.^[5] TNF-α also trended to decline in both groups, and MCP-1 in females.^[5] This currently is the only study to measure baseline cytokines (biomarkers of inflammation), with other human interventions of moderate quality all suggesting an improvement of natural killer cell activity.^[13][144]

There is currently limited evidence in humans when examining all parameters, but spirulina shows some early trends of increasing natural killer cell activity while concurrently lowering systemic inflammation

In rats, reductions of TNF-α have been noted at doses as low as 25mg/kg bodyweight basic Spirulina extract.^[148]

8.1. General

Spirulina, in general, can protect cells from death via its anti-oxidative properties if the death to the cell was caused by oxidative means; general anti-oxidant properties.^[154] In a comparative study against Vitamin C, it was noted that Spirulina was able to reduce free-radical induced death by 2-5 fold, but was less effective than vitamin C at the same concentrations tested (125, 250mcg/mL).^[154]

8.2. Interventions

A comparative study between Spirulina and Wheat Grass (Triticum aestivum) at 500mg twice daily for 30 days demonstrated that both compounds had anti-oxidative capacities, but the changes were greater with Wheat Grass and failed to reach significance with Spirulina.^[155] MDA, plasma Vitamin C, and intrinsic anti-oxidant enzymes were assessed.^[155]

9.1. Testosterone

In a rat model of testicular toxicity, Spirulina is able to preserve testosterone levels despite oxidative toxins while the group given Spirulina without the toxin (mercury) did not experience an increase in testosterone.^[51]

9.2. Leptin

A study in obese mice (secondary to fatty liver) noted that Spirulina was able to decrease circulating leptin levels closer to lean control levels when compared to obese control and obese rats given 0.02% pioglitazone.^[130]

10.1. General Mutagenicity

In a rat model of cyclophosphamide-induced mutagenicity Spirulina at 200, 400, and 800mg/kg for 2 weeks prior to 5 consecutive days of cyclophosphamide was tested and the anti-mutagenic/anti-genotoxic effects investigated.^[156] The increase in implantation losses in pregnant mice was significantly reduced at all doses and normalized the sperm abnormalities seen with the toxin (sperm count, motility, shape).^[156]

In studies that measure DNA fragmentation in healthy cells in response to toxins (a process seen as carcinogenic), Spirulina at 50mg/kg is able to reduce a 31.2% increase in DNA fragmentation by aflatoxin to 8.8% in the liver and reduced a 10.2% increase to 0.9% in the testes; this study noted that Spirulina reduced DNA fragmentation by 1.3% in the liver when no toxin was ingested, and the protective effects were nonsignificantly additive with whey protein.^[157]

10.2. Immunological Interactions

Spirulina appears to have the capacity to reduce tumor size or otherwise retard tumor growth rates secondary to increasing Natural Killer cell activity,^[145] although other studies note reduction in tumor size and do not draw a link between said observation and NK cells.^[158]

10.3. Oral

One intervention in Kerala India measuring oral leukoplakia in tobacco users noted that 1g Spirulina daily for a year was associated with complete regression of lesions in the oral cavity in 45% of persons in this group, relative to 7% in placebo; upon cessation of supplementing Spirulina, 9 of the 20 responders developed the lesions the following year without Spirulina.^[159]

Low dose spirulina (1g) has been noted to decrease the rate of oral lesions in tobacco users, although it did not confer complete protection to all participants

10.4. Melanoma

One in vitro study investigating the polysaccharide of Spirulina known as Calcium Spirulin noted that B16-BL6 Melanoma cells had 50% reduced invasion (Matrigel/fibronectin-coated filters) at 10mcg/mL concentration, and reduced migration to laminin (but not fibronectin) filters in a dose-dependent manner; similar effects were noted with colonic M3.1 and fibrosarcoma HT-1080 cells.^[160]

10.5. Colon

C-phycocyanin (from the protein fragment of Spirulina) is associated with protecting from colon cancer in part due to its ability to inhibit excessive production of COX-2 in colon cells,^[161] which tends to be increased in colon cancer cells.^[138] Many studies pair C-Phycocyanin with Piroxicam, which is a nonselective COX1/2 inhibitor, and the benefits appear additive.^{[139][162][163]}

Daily injections of 200mg/kg C-Phycocyanin can normalize Akt/PI3k activation and concurrently raise PTEN and GSK-3β activation,^[139] which is additive with the NSAID inhibitor Piroxicam, where 4mg/kg Piroxicam and 200mg/kg C-Pycocyanin inhibited 92.33% of colonic inflammation in response to the toxin dimethylhyadrazine (DMH), with C-Phycocyanin itself inhibiting 72.33% of inflammation (more effective than 4mg/kg Piroxicam at 62.33% and 5mg/kg Indomethacin at 67%)^[163] and reduced the amount of abberant crypt foci (indicative of polyp formation) by 65% in isolation, and 75% with Piroxicam.^[163] This same dose of C-Phycocyanin (200mg/kg) also reduced DMH lesion incidence from 100% to 66% over 6 weeks of treatment, acted to normalize histological changes, and was found to increase the amount of apoptotic cells from approximately 7% to 30% (data derived from graph, similar potency to 4mg/kg Piroxicam and combination is additive).^[162]

In studies measuring cell colonies, less aggregation is noted following both C-Phycocyanin and Piroxicam (Spirulina nonsignificantly more effecitive, reducing the DMH control of 57.49% to 16.53%) and both antiinflammatories increase cell count in early (from 3.34% in DMH control to 20.43% with C-Phycocyanin) or late (2.45% to 33.66%) stage apoptosis.^[139]

C-Phycocyanin is able to exert a large protective degree against 1,2-dimethylhyadrazine induced carcinogenesis, which is slightly (sometimes nonsignificantly) more effective than 4mg/kg Piroxicam when 200mg/kg C-Phycocyanin is used, additive with Piroxicam

11.1. Muscle Hypertrophy

A study conducted in young rats (30 day old pups) comparing a diet with 17% Spirulina (64% protein by weight) against 17% casein protein (84% protein by weight) as the sole protein source over the course of 60 days noted that although total muscle weight, size, and DNA content were similar in both groups that Spirulina had 44% higher levels of the contractile protein Myosin, suggestive of increased protein synthesis rates relative to casein.^[164] No significant differences were observed in the Actin protein component.^[164]

Though too preliminary to guess how it would work in humans, there appears to be a more hypertrophic effects from the spirulina protein source in young rat pups when compared to casein protein

11.2. Power Output

One study on untrained university students as well as trained (3 years of activity or greater) noted that Spirulina, taken at 2g daily for 8 weeks, found increased peak force output in both the trained and untrained subjects that used Spirulina alongside training (relative to placebo combined with training) but no significant influence was seen on muscular endurance as assessed by 60 second isometric.^[165] Dietary analysis' were not conducted in this study.

Only one human study was conducted in power output, which showed improvement, but a lack of dietary analysis precludes any conclusions that could be drawn from this

11.3. Endurance and Time to Exhaustion

A study conducted in healthy youth (20-21yrs) noted that 3 weeks of supplementation with Spirulina at 7.5g daily (2.5g taken with a meal thrice a day; 53.3% protein and 33.3% carbohydrate) was associated with an increased time to exhaustion as assessed by treadmill running.^[4] While placebo improved their times by 23 seconds at follow-up (3.2% improvement) Spirulina was associated with an increase of 52 seconds (7.3%).^[4] This study also noted significantly less lactate dehydrogenase (79.3% of control) and more lactate (138% of control) when blood was taken 30 minutes after exercise, although a high interindividual range existed.^[4] The only other study to measure lactate was at complete rest, and noted a non-significant trend to increase in runners.^[103]

These results have been replicated, as 6g of Spirulina for 4 weeks was associated with an improved time to exhaustion (131% of control) after subjects were pre-exhausted with a 2 hour run; this study was conducted in moderately trained athletic men, and this was thought to be secondary to the increase in fat oxidation (+10.9%) preserving carbohydrate storages (glucose oxidation decreased by 10.3%).^[166]

Spirulina has repeatedly shown to improve endurance exercise performance at practical doses in human subjects that are otherwise healthy

11.4. Chronic Fatigue

In a series of case studies with Spirulina (4) where each patient was their own cross-over ontrol, it was suggested that Spirulina at 3g daily for 4 weeks did not possess the ability to aid in idiopathic (without disease state) chronic fatigue.^[167]

12.1. Interventions

A study in rats in which said ovariectomized rats (a model to mimic menopause) fed Spirulina at 80mg/kg, 800mg/kg or 4g/kg bodyweight with 0.2% calcium (by weight in diet) and compared to a Spirulina free diet noted that no differences in body weight existed (despite increases in food intake with Spirulina) and Spirulina was associated with a decrease in bone mineral density under estrogen deficient conditions.^[168]

13.1. Mechanisms (Hepatoprotection)

The anti-oxidative effects of Spirulina at 1g/kg oral ingestion for 5 days prior to a cisplatin injection was able to attenuate damage to the liver (histological examination) and combining Spirulina with 500mg/kg Vitamin C appeared to abolish cisplatin-induced liver damage.^[169] Protective effects on the liver from toxins have also been established against D-galactosamine and Acetominophen with 3-9% dietary Spirulina in rats.^[170]

13.2. Liver Enzymes

One rodent study on fructose-induced insulin resistance noted that Spirulina at low doses (0.33g/kg in rats) was associated with decreased SGOT (-33.42%) and SGPT (-24.78%) levels in serum, their increase of which indicates hepatocellular necrosis and membrane damage and their reduction indicative of less liver cell damage.^[104] Reductions in SGOT and SGPT have been noted in humans, but after 2 or 4g Spirulina for 3 months they were from 21.1 to 16.7 (-20.9%) with 2g and 19.4 to 15.5 (-20.1%) with 4g and both were not statistically significant in these otherwise healthy persons with elevated cholesterol, as placebo also saw a decrease of 18.8%.^[109]

Spirulina attenuated the increase in liver enzymes (ALP, AST, ALT) in response to Cisplatin injections while the combination of Spirulina (1g/kg) and Vitamin C (500mg/kg) effectively normalized levels of liver enzymes.^[169] These particular enzymes have also been noted to be reduced following oxidative damage paired with a high fat diet, where 2-6g Spirulina dose-dependently reduced both ALT and AST.^[147]

13.3. Fibrosis

It has been hypothesized that Spirulina, via NADPH oxidase inhibition, could inhibit proliferation of stellate cells and serve as a therapeutic alternative in instances of liver fibrosis.^[171] This hypothesis is based on suppression of stellate cell proliferation by activation of the ERb receptor (via one of the soy isoflavones Genistein^[172] and in part estrogen itself^[173]) working vicariously through suppressing NADPH oxidase activity, as well as DPI (a research chemical that inhibits NADPH activity) has also been shown to reduce stellate cell proliferation.^[174][175]

13.4. Steatohepatitis (Fatty Liver)

Spirulina has the ability to reduce fatty liver (steatohepatitis) in various animal models, including fructose-induced obese rats,^[104], MSG-induced obese rats (where cerebral injections of MSG into newborn rats induces fatty liver via overeating^[176]),^[130] choline-deficient high fat diet injected with a pro-oxidant (2-6g/kg Spirulina).^[147]

Studies that compare Spirulina to reference drugs or practises note that Spirulina (5% of feed intake) being more effective than 0.02% pioglitazone at reducing hepatic triglyceride content and cholesterol,^[130] 17% Spirulina (very high dose) being more effective than minor cardiovascular exercise at improving lipid profiles with additive benefits to lowering cholesterol (similar reductions in liver fat between groups at 43-46% of control),^[106]

Spirulina may also act in a preventative manner, where the increase in liver fat in response to a high fat, cholesterol, and alcohol diet with additional statin drugs was halved with Spirulina supplementation.^[177]

In rats, spirulina shows rehabilitative and preventative mechanisms to reduce liver fat buildup. The effect seems potent

These mechanisms have been tested in humans, and in a series of case studies where three persons were treated with 4.5g Spirulina for 3 months each and later assessed by ultrasound found an average decrease in ALT by 41%, including the third case where the pathological level of ALT was reduced 34%.^[178] Triglycerides, total cholesterol, LDL-C, and the cholesterol:HDL-C ratio all decreased on average by 19%, 16%, 22% and 18%; respectively. This was thought to be secondary to universal improvements in the levels of fatty liver seen via ultrasound (biopsies not taken).^[178]

Spirulina may be able to reduce fatty liver build-up as induced by the diet and appears to be quite potent at doing so independent of lifestyle changes (and even with combined statin and alcohol usage in rats), with limited human evidence showing just as promising results. It appears to be quite moderately potent, but quite reliable

13.5. Virology

Components of Spirulina appear to hold relatively general anti-viral effects in vitro, with relative affinity for the herpes simplex virus with an EC₅₀ of 0.069mg/mL.^[179]

In a trial of persons with chronic hepatitis C infection, Spirulina was compared against Silymarin (isolated from Milk Thistle) and both treatments had a degree of efficacy at inducing a sustained virological response (suppression of the virus to undetectable levels); Spirulina trended to be better than Silymarin but was not statistically significant.^[180] In this 6 month trial, 4 persons (13.3%) achieved a sustained virological response while 2 others (6.7%) had partial benefits and the other 80% not responding; Silymarin only had one sustained virological response (3.4%) and the rest did not response.^[180] Responders had low baseline viremia. Another study on HIV failed to notice any benefit to abnormal liver enzymes associated with Spirulina^[181] and a third pilot study combining Spirulina with Undaria Pinnatifida (common source of fucoxanthin) noted that with the HIV/AIDS virus that quality of life improved after 3 weeks of either supplement of combination therapy (of 2.5g Undaria and 3g Spirulina), and a sole subject (case study) used treatment for a year and reduced his virologic load while increasing CD4+ immune cell count from 474 to 714 CD4/uL (+50%).^[182] 

The anti-viral effects of spirulina appear to be active after human consumption despite spirulina's non-toxicity at tested doses of up to 5g, and may confer some symptom relief associated with viral disorders over the short term or act in opposition of the virus over the longer period. There is not enough evidence to suggest reliability of treatment

Although spirulina appears to be one of the more potent supplements for improving virological status (based on preliminary evidence at least), this does not appear to be a topic where nutritional supplementation holds much potency

13.6. Anemia

One study has been conducted in older persons with a history of anemia taking 3g of Spirulina daily for 12 weeks failed to note an increase in red blood cell count yet increased mean corpuscular hemoglobin (MCH), MCV, and MCHC in men and increased in MCH in women.^[183] Platelets were unchanged over 12 weeks, and white blood cells increased significantly at 6 weeks in time; high variability noted in this study.^[183]

Spirulina may aid anemic symptoms, but evidence is preliminary

14.1. Thymus

Thymus atrophy can be induced by Tributyltin via pro-oxidative means, which can be almost abolished when the C-phycocyanin from Spirulina is pre-loaded (this study, however, used injections) of 70mg/kg bodyweight.^[184] Although control had reduced size to 30% of untreated control, coingestion of the toxin and C-phycocyanin had 90% control size, and the protection was hypothesized to be secondary to the antioxidative abilities of C-phycocyanin.^[184]

14.2. Kidneys

C-Phycocyanin and/or Spirulina are able to protect the kidneys from from various toxic insults including mercury chloride (reducing grade 4 histology damage to 'minor' damage at 100mg/kg C-Phycocyanin^[9]), cisplatin (50mg/kg C-Phycocyanin),^[185][186] cyclophosphamide (1,000mg/kg of spirulina),^[187] 4-nitroquinoline-1-oxide (500mg/kg Spirulina),^[23] and Gentamycin.^[188] These renal toxins exert their damage via oxidative stress.

C-Phycocyanin appears to be highly protective of the kidneys via various toxin-induced stressors, with combined anti-inflammatory and anti-oxidative mechanisms

Heptadecane (volatile) has also been implicated in preserving renal function in isolation at 2-4mg/kg in rats, where the increase in reactive oxygen species (ROS; inherent in vivo and induced by t-BHP in vitro) and NF-kB activity seen with aging were normalized in a dose-dependent manner, and in vitro the oxidation-induced NF-kB activity was slightly attenuated at 1-20µM.^[20]

Heptadecane may also be a bioactive of interest, but appears to be less potent than C-Phycocyanin

14.3. Lungs

The fibrotic effects of paraquat toxicity can be alleviated with 50mg/kg C-Phycocyanin in rats.^[189]

14.4. Testes

The oxidative damage to the testes induced by mercury has been noted to reduce serum and testicular lipid peroxidation at 300mg/kg spirulina intake, which was associated with less (35%) mercury accumulation in the testes.^[51] This study also noted that, relative to untreated control, the group given Spirulina in isolation experienced increases in oxidative enzymes (6.3% SOD and 9.2% GSH) with reductions in blood lipid peroxidation (14.8%).^[51]

15.1. Whey Protein

The combination of Spirulina and Whey Protein concentrate was because due to both being complete protein sources, Spirulina is relatively low in the amino acid Cysteine whereas many of Whey Protein's benefits are secondary to being a high source of Cysteine. In a study where 2.5mg/kg Spirulina and 300mg/kg Whey Protein were consumed either in isolation or combined for 30 days, it was found that Whey Protein was nonsignificantly better at reducing lipid peroxidation in the liver and testes and the combination conferred no additional benefits while the combination conferred non-significant benefits to improving glutathione status in these organs.^[157] Both were effective in reducing pathology associated with aflatoxin infection as well, with minor differences and little additive effects.^[157]

A whey-spirulina mix may be a good combination to round out dietary amino acids, but it is less than additive in regards to anti-oxidation in the liver

15.2. NT-020

NT-020 is a combination of polyphenols from blueberry, green tea catechins, carnosine (from beta-alanine) and Vitamin D^[190][191] and this combination supplement appears to be synergistic with spirulina in enhancing stem cell proliferation (CD34+ derived bone marrow cells). Although the exact molecule(s) mediating the synergism are not known, it was calculated at being 50% greater than the additive benefits.^[98] The mechanism of synergism appeared to be via spirulina suppressing TNF-α induced suppression of stem cell proliferation, while some other agent was able to induce stem cell proliferation (and worked better when TNF-α could not act).^[98] NT-020 overall is known to do this^[192][193] in a synergistic manner itself^[190] with all bioactives being somewhat active (hypothesized to be secondary to reducing oxidative stress^[190]).

Spirulina is able to suppress the actions of a negative regulator of stem cell proliferation, which allows the nutraceutical combination of NT-020 to induce stem cell proliferation. Due to this and all bioactives of NT-020 being active, spirulina is likely synergistic with all individuals components (blueberries, carnosine, green tea, and vitamin D)

16.1. General

When tested in animals, doses up to 5% of the diet as Spirulina (by weight) for periods of up to 6 months are not associated with any salient toxicological effects, and in this study no detected microcystin contamination existed up to 20-50ng/g^[194] and a 13 week study using 30% of the diet as spirulina^[195] or 5000mg/kg isolated Phycocyanin (approximately equivalent to 25g/kg spirulina)^[122] have both failed to exert any toxic effects. A slight increase (2.5%) of ALT has been noted with a related bacterial strain (Nostoc commune).^[196]

A safety evaluation was conducted by the United States Pharmacopoeia (USP)^[197] and reviewing Pubmed literature from 1966 to October 2009 as well as FDA adverse-event reports (78 total, 38 confounded with ephedra and others confounded with toxic bacteria; only 5 reported cases of liver damage and 8 other adverse events) concluded that Spirulina has no sufficient evidence to suggest harm associated with it and designated a Class A safety assignment to both Spirulina Maxima and Platensis.^[197] The possibility of microcontamination from microcystins causing the reported cases of liver damage was noted, as well as calls for research in more populations.^[197]

It was noted^[197] that a critical issue with Spirulina safety is that its source coexists with bacteria and is itself a cyanobacteria. The cyanobacteria genera Spirlina comes from appears to be free of known toxins, but related genera (Aphanizomenon and Microcystis) are known to have toxic species and may co-exist with Spirulina in production,^[198] the production of these strains being somewhat unpredictable and requiring quality control after the fact.^[197] Microcystins may also be produced, which are produced from other blue-green algae (not spirulina) that are protein phosphatase inhibitors, and have been shown to induce liver damage and the prototypical microcystin has an LD₅₀ value of 5mg/kg.^[199]

There is currently no evidence to suggest general harm associated with spirulina per se, but possible contaminations of spirulina with other non-spirulina blue-green algae (which appear similar by the naked eye) that may produce toxic metabolites. This is an issue of quality control

16.2. Case Studies

One case study exists between rhabdomyolysis and Spirulina.^[200] This case involves a 28 year old man taking 3g Spirulina (Hawaiin Spirulina from Solgar Vitamin and Herb) daily for a month, with no other drug usage or illnesses. Symptoms ceased after a short stay in hospital and cessation of the supplement, and it was deemed Spirulina was likely the cause; this is currently the only reported Rhabdo case associated with Spirulina.^[200] These authors also hypothesized possible production of a neurotoxin from Spirulina (BMAA, β-N-methylamino-L-alanine) which is produced in some Cyanobacteria such as Nostoc but could not establish this; no current literature suspects BMAA contamination in Spirulina.

Another case study associated with two bacteria strains (Spirulina Platensis and A. flos-aquae) were implicated in a case of dermatomyositis in a 45 year old woman using these bacteria alongside red pepper extract (capsaicin) and methylsulfonylmethane (MSM). Causation could not be placed on Spirulina yet clinical signs were associated with usage, cessation, and reconsumption of the product and the patient suffered from a genetic susceptibility to immunostimulants (which is in line with Spirulina's biological activities).^[201] It is plausible that Spirulina caused these symptoms, but cannot be proven.

Finally, a third case study noted liver toxicity associated with Spirulina.^[202] In this case, a 52 year Japanese man with a history of hypertension and high blood lipids (and past usage of statin drugs) that experienced elevated liver enzymes after 5 weeks of usage of Spirulina; this case is problematic as statins drugs may cause hepatotoxicity in rare cases and Spirulina was ceased (and symptoms disappeared) at the same time all drugs were ceased; causation cannot be placed.^[202]

There are three case studies on spirulina, two of which may suffer from product contamination, while the last may have legitimate biological plausiblity for spirulina inducing immune system hyperactivity. Causation has not been assigned to the spirulina bacteria yet, but the specific products used in two studies appear to be connected

16.3. Allergies

Despite Spirulina normally being beneficial for allergies, at least one reported case involving a 14 year old boy consuming a standard dose of Spirulina noted that an allergic response occurred 6 hours after consumption, and causation appears to have been placed in this case on the C-phycocyanin component.^[203]