Spirulina

1.1. History

Spirulina is a colloquial term for a large number of Cyanobacteria in the Spirulinaceae family.^[1] The most commonly used spirulina species in dietary supplements are S. maxima and S. platensis.^[1] Cyanobacteria, including spirulina, are often referred to as blue-green algae despite being prokaryotic (algae are eukaryotic).

Spirulina has been part of the human diet since at least the 16th century, when French researchers documented the consumption of sun-dried spirulina (called “Dihe”) by the native African population in modern-day Republic of Chad.^[2] There is also evidence of Spirulina being harvested and traded by the Aztecs in Central America during this time.^[2]

Spirulina refers to a group of cyanobacteria, the two most common being S. maxima and S. Platensis. It has been part of the human diet since at least the 16th century.

1.2. Sources

Spirulina can grow anywhere conditions allow, but is most concentrated in Lake Texcoco of Mexico, Lakes Chad and Niger of Central Africa, and along the Great Rift Valley of East Africa.^[3] It thrives in high-salt (>30 g/L), alkaline (pH 9–11) waters where survival of other microorganisms is difficult or impossible.^[4] Spirulina relies exclusively on photosynthesis to survive.

Most commercial production systems are based on shallow raceways in which spirulina cultures are mixed by a paddle wheel.^[3] The United States of America has several of the largest intensive farms in the world, based in Hawaii and California. Other countries of major production are China, India, Thailand, Vietnam, and Taiwan.

Spirulina production has eight main stages: filtration and cleaning, preconcentration, concentration, neutralization, disintegration, dehydration, packing, and storage. These processes act to concentrate spirulina, remove its salt and water content, and prepare it for distribution.^[3]

Quality control for food-standard spirulina includes microbiological standard tests, chemical composition tests, and tests for contaminants like heavy metals, pesticides, and extraneous materials (insect fragments, rodent hair, etc.).^[3]

Spirulina thrives is high-salt, alkaline waters where growth for many other microorganisms is difficult. Although spirulina can be found growing in the wild, it is most commonly farmed to ensure better quality control.

1.3. Properties

On a dry-weight basis, spirulina is 60–77% protein, 9–15% lipids, and 10–19% carbohydrates, with variation depending on spirulina species and growing conditions (e.g., pond versus lab-grown).^[2] The protein content is of relatively high quality for a plant-based protein, having a biological value of 75% and a digestibility of 83%.^[2]

A portion of spirulina’s protein content comprises a protein-bound photosynthetic pigment called C-Phycocyanin, which has demonstrated anti-inflammatory, antioxidant, antitumor, and immunostimulating properties.^[5] These effects are owed, in part, to the phycocyanobilin constituent of C-Phycocyanin, which is a close analogue of human bilirubin that functions to inhibit NADPH oxidase activity.^[6] 

C-Phycocyanin comprises about 20% of spirulina’s dry weight when spirulina is freeze-dried or sun-dried, but only about 4% of dry weight when oven-dried.^[7] Phycocyanobilin makes up about 5% of C-Phycocyanin, or up to 1% the dry weight of spirulina.^[8] 

Spirulina also contains immunostimulatory bioactive carbohydrates, called Immulina, at 0.5–2.0% dry weight,^[9] and γ-Linolenic acid (C18:3, ω6, GLA) at about 20% of the total fatty acid content (18–30 mg/g dry weight).^[10] 

Spirulina is a source of several minerals, including iron (0.38–0.54 mg/g), calcium (1.48–1.8 mg/g), magnesium (2.7–3.98 mg/g), zinc (0.056–0.058 mg/g), manganese (0.024–0.033 mg/g), and copper (5–10 µg/g).^[11] Spirulina also contains vitamin B12 (0.56 µg/g) and pseudovitamin B12 (7-adenyl cyanocobamide; 2.74 µg/g),^[12] the latter of which is not readily usable by humans and has a binding affinity to intrinsic factor that is about one-third that of true vitamin B12.^[13]

Finally, spirulina is a source of various carotenoids, including zeaxanthin (0.12–1.27 mg/g), β-carotene (0.02–2.3 mg/g), and chlorophyll a (2.6–10.8 mg/g).^[14] The consumption of spirulina is positively correlated with vitamin A status in native African women,^[15] and its β-carotene appears to be twice as bioavailable as that found in spinach (4.5:1 versus 9:1 ratio of β-carotene to retinol conversion).^[16] Similarly, consuming 4–5 grams of spirulina is capable of increasing zeaxanthin status.^[17] 

Spirulina is a high-protein food product rich in several bioactive compounds and micronutrients. It’s most well-known bioactive compound is C-Phycocyanin, which comprises about 20% of spirulina’s dry weight.

1.4. Biological Activity

Spirulina’s spotlight role in clinical medicine is believed to be owed to its phycocyanobilin content, a compound structurally similar to unconjugated (free) bilirubin.^[6] Free bilirubin is a known inhibitor of NADPH oxidase in the low nanomolar concentrations of normal physiology.^[18] Phycocyanobilin also inhibits NADPH oxidase.^[6]

NADPH oxidase is a free radical-generating enzyme complex activated by inflammatory cytokines and infections.^[19] NADPH oxidase activation is vital for innate immunity, but excess signalling can contribute to the oxidative stress load underlying many disease states,^[20] such as type-2 diabetes.^[21] 

People who have genetically elevated free bilirubin levels, a clinically benign autosomal recessive disorder called Gilbert’s syndrome,^[22][23] display lower rates of death from any cause (-50%) compared to the general population,^[24] as well as lower levels of oxidative stress^[25] and cardiovascular morbidity and mortality.^[26][27] 

In animals, using drugs to increase production of free bilirubin, termed “Iatrogenic Gilbert syndrome'',^[28] and administering free bilirubin directly have demonstrated benefits towards obesity, metabolic syndrome, and type-2 diabetes.^[29] Several drugs have also been explored for health benefits through directly inhibiting NADPH oxidase.^[30] 

Spirulina’s health effects are believed to be owed primarily to its phycocyanobilin content, which is structurally similar to bilirubin and, like bilirubin, acts to inhibit NADPH oxidase. The inhibition of NADPH oxidase reduces oxidative stress and may be an underlying factor in the health benefits associated with Gilbert’s syndrome, a condition characterized by high levels of free bilirubin.

2.1. Toxicity

The Dietary Supplements Information Expert Committee of the United States Pharmacopeia reviewed the safety of spirulina in 2011.^[1] The committee unanimously voted for a Class A safety assignment for spirulina, meaning that available evidence did not indicate it to pose a serious health risk when properly formulated and used.

Rather, the committee noted that the primary concern with spirulina was the potential for contamination with other cyanobacteria that produce hepatotoxic and carcinogenic microcystins, as well as potential contamination with heavy metals such as mercury, cadmium, lead, and arsenic.^[1] Microcystins are not produced by spirulina.

Studies in mice with unadulterated spirulina reported no adverse effects of consuming 30% of the diet from spirulina for 13 weeks,^[31] or from consuming 5% of the diet as spirulina for six months.^[32] 

Evidence suggests that spirulina does not pose a health risk, although it may be contaminated with things that do.

2.2. Side Effects and Adverse Events

A double-blind, randomized placebo-controlled trial in adults with chronic pain reported no adverse events associated with supplementing with 2.5 grams per day of a C-phycocyanin-rich spirulina extract (40% C-phycocyanin by weight; 1 g/d) over two weeks.^[33] Tests included those of blood chemistry, heart function, blood pressure, and platelet function.

One case study has documented an allergic reaction to spirulina believed to be owed to its C-Phycocyanin component.^[34] The allergic reaction began within six hours of consuming 2.5 grams of spirulina, in a 14-year-old adolescent.

A case study has documented an allergic reaction to spirulina, but there appear to be no known other adverse events

2.3. Degradation, Adulteration, Contamination

Spirulina may be contaminated with toxic microcystins produced by other bacteria (not spirulina) growing in spirulina’s vicinity.^[1] The safe consumption level for microcystins is set at 0.04 µg/kg/d.^[35]

An early analysis of 15 commercial spirulina supplements reported that average microcystin concentrations were 0.15 µg/g (range: 0.06–0.32 µg/g) in 1998 and 0.52 µg/g (range: 0.0–2.12 µg/g) in 1999.^[36] Accordingly, an 80 kg (176 lb) adult could safely consume up to 6–21 grams of spirulina (3.2 µg of microcystins) based on the two reported average contamination levels.

Quality control standards appear to have improved more recently, however, as a 2017 analysis of 14 commercial spirulina supplements reported that only 3 had detectable levels of microcystins (0.21, 0.24, and 0.84 µg/g).^[37] Other recent analyses also reported that spirulina supplements from U.S.,^[38] German,^[39] and Italian^[40] markets were free of detectable levels of microcystins.

Another contamination issue with spirulina is the accumulation of heavy metals, because spirulina has a unique ability to to chelate and neutralize toxic heavy metals, such as removing arsenic from food, water, and the environment.^[1]

An analysis of 25 spirulina supplements manufactured in seven different countries (U.S., Canada, U.K., New Zealand, Japan, India, and Australia) reported that mercury and platinum concentrations were below detectable limits in most every sample.^[41] Another analysis of 11 spirulina supplements from around the world found that mercury (0.02–0.11 µg/g) and cadmium (0.01–0.17 µg/g) were well below safety limits and that no lead or arsenic could be detected.^[42]

This latter study also reported that pesticide contamination of spirulina was low in 3 of the 11 samples and not detected in the others, and that mycotoxins or acrylamide were undetected.^[42]

Spirulina may be contaminated with hepatotoxic and carcinogenic microcystins, as well as potential with heavy metals such as mercury, cadmium, lead, and arsenic. Recent testing of commercial supplements suggests that microcystins, mycotoxins, heavy metals, and pesticides are largely a non issue.

3.1. Mineral Detoxification

Cyanobacteria tends to be an accumulator (biosorbent) of heavy minerals ex vivo^[43][44][45] due to ion-exchange binding^[46] 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^[47] which has been noted elsewhere^[48]); bioactives in the hexane extract appear more potent than the alcoholic extract.^[47][48]

Spirulina (250-500mg/kg) has shown efficacy in preventing mineral toxicity form occurring in pregnant rats' offsprings when the mothers were given fluoride^[49] 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).^[50] Protective effects in pregnant rats on their pups have been noted with cadmium as well.^[51]

In male rats, 300mg/kg can attenuate mercury accumulation in the testes (which is thought to partially contribute to antioxidative effects)^[52] and protection against mercury has been noted elsewhere in kidneys (800mg/kg spirulina in mice).^[53] The other species of cyanobacteria known as spirulina fusiformis (also a source of C-Phycocyanin^[54]) appears to also possess testicular protective effects against mercury^[55] and to reduce serum biomarkers of mercury toxicity^[56] (similar to spirulina itself^[57])

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^[50] 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^[58] and seems somewhat comparable to an equal dose of Liv-52 (Ayurveda combination formula) at reducing both cadmium^[59] and lead^[60] toxic effects, although they were not additive.^[59][60]

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.^[61] 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.^[61] 

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

3.2. 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.^[62] CYP1A2 and CYP2E1 are also downregulated, but this is associated with reductions in mRNA and protein levels.^[62]

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.^[62]

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

3.3. 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.^[63] 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.^[63] 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)^[63] and has been reported elsewhere in non-carcinogenic tissue^[64] and regular macrophages treated with the pro-oxidant 2-acetylaminofluorene.^[65]

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.^[66]

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

A double-blind, randomized placebo-controlled trial in adults with chronic joint pain reported significant reductions in pain at rest and when active when supplementing with 2.5 grams per day of a C-phycocyanin-rich spirulina extract (40% C-phycocyanin by weight; 1 g/d) over two weeks.^[33]

One small study suggests that spirulina reduces joint pain in people with chronic joint pain.

5.1. 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^[6] 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

5.2. 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.^[8]

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

5.3. 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)

5.4. 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

5.5. 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

6.1. Cardiac Function

A double-blind, randomized placebo-controlled trial in adults with chronic pain reported no significant effect on heart function (EKG) of supplementing with 2.5 grams per day of a C-phycocyanin-rich spirulina extract (40% C-phycocyanin by weight; 1 g/d) over two weeks.^[33]

Spirulina doesn’t appear to affect heart function.

6.2. Hemodynamics

A meta-analysis of 4 studies reported that spirulina supplementation significantly reduced diastolic blood pressure (-7 mmHg) and tended to reduce systolic blood pressure (-3.5 mmHg) compared to control.^[102] 

Rodent studies suggest that spirulina’s hypotensive effects may be owed to direct endothelium-dependent vasodilation from nitric oxide production,^[103] as well as altering the balance of cyclooxygenase products such that the arachidonic acid metabolite prostacyclin is favored over thromboxane.^[104] Also in rodents, combining spirulina with strength training may potentiate the hypotensive effects of spirulina.^[105] 

A double-blind, randomized placebo-controlled trial in adults with chronic pain, using 2.5 grams per day of a C-phycocyanin-rich spirulina extract (40% C-phycocyanin by weight; 1 g/d) over two weeks, reported no significant difference from placebo for changes in platelet aggregation, platelet P-selectin expression, or blood clotting factors (activated partial thromboplastin time, thrombin time, and fibrinogen activity).^[33] 

Mechanistically, however, C-phycocyanin appears to have a concentration-dependent effect on platelets, reducing their aggregation and clotting ability by inhibiting intracellular Ca²⁺ mobilization and thromboxane A2 formation.^[106] 

Spirulina significantly reduces blood pressure in a meta-analysis of mostly unhealthy populations due to promoting vasodilation and nitric oxide production. Despite having the biological ability to interfere with platelet function, a controlled trial in adults suggest it doesn’t.

6.3. Lipid and Cholesterol Absorption

A study in young runners found that taking 5 grams of spirulina per day for two weeks significantly lowered post-meal triglyceride levels compared to baseline (-20%).^[107] Reductions in post-meal serum triglycerides were seen at 1.5, 3, and 4.5 hours following the meal, occured in 62% of participants, and were most pronounced in participants aged 10–12 years (-30%).

A study in rats has reported that spirulina and its C-phycocyanin content inhibit both jejunal cholesterol absorption and ileal bile acid reabsorption.^[108] 

Spirulina appears to inhibit the absorption of lipids.

6.4. Blood Lipids and Lipoproteins

A meta-analysis of 12 studies with 807 participants reported that spirulina supplementation significantly affected LDL-C (-33 mg/dL), triglycerides (-39 mg/dL), vLDL-C (-8 mg/dL), and HDL-C (+6 mg/dL) compared to placebo (n=7) or no intervention (n=5).^[102]

Studies lasted an average of 2–12 weeks (average: 12 weeks), administered 1–19 grams of spirulina per day (average: 2 grams), and involved mostly unhealthy populations (e.g., type 2 diabetes, hypertension, and heart disease patients). Subgroup analyses suggested that blood lipid benefits were statistically significant only in trials lasted 12 weeks or longer and using 2 grams or more of spirulina.

An earlier meta-analysis of 7 studies with 522 participants found similar significant effects on LDL-C (-41 mg/dL), triglycerides (-44 mg/dL), and HDL-C (+6 mg/dL) compared to control.^[109] 

Spirulina significantly lowers LDL-C, vLDL-C, and triglycerides, while raising HDL-C, in meta-analyses of mostly unhealthy populations.

7.1. Insulin Sensitivity

In obese adults with treated hypertension, 2 g/d of spirulina for three months significantly increases insulin sensitivity (via the euglycemic-hyperinsulinemic clamp) compared to placebo.^[110] Insulin sensitivity increased by 34% in the spirulina group and declined by 12% in the placebo group.

Spirulina has also shown promise as adjunct therapy to highly active antiretroviral therapy (HAART) in patients with HIV,^[111] since HAART is associated with insulin resistance.^[112] In HIV patients, supplementing with 19 g/d of spirulina increased glucose disposal (+56%) and insulin sensitivity (+165%) compared to control.^[111]

Spirulina may increase insulin sensitivity in obese adults and patients with HIV undergoing standard care.

7.2. Blood Glucose and Insulin

A meta-analysis of eight studies reported that spirulina supplementation significantly lowered fasting blood glucose by an average of 5 mg/dL.^[102] No subgroup analysis was performed. Studies involved adults with type 2 diabetes (n=3), HIV (n=2), hypertension (n=1), and obesity alone (n=2); used 1–19 grams per day (median: 2 grams); and lasted 2–24 weeks (median: 12 weeks).

Spirulina may reduce fasting glucose by a clinically insignificant amount.

7.3. Glycation

A meta-analysis of three studies reported that spirulina supplementation did not significantly lower HbA1c.^[102] 

Spirulina may not affect HbA1c.

7.4. Diabetes

A study involving 25 elderly adults with type 2 diabetes reported that supplementation with 2 grams of spirulina per day for two months significantly reduced fasting blood glucose (-19 mg/dL or -12%), 2-hour postprandial glucose (-16 mg/dL or -6%), and HbA1c (-1.0%; from 9% down to 8%) compared to baseline, whereas these glycemic parameters remained unchanged in the control group.^[113] No statistical analysis was performed between groups.

Another study of people with type 2 diabetes reported significant reductions in fasting and postprandial glucose levels with the use of either 1 g/d or 2 g/d of spirulina, whereas no improvements were seen in the control group.^[114] However, statistical differences between groups were not performed.

However, a third study using 8 g/d of spirulina over 12 weeks reported no benefits for fasting glucose or HbA1c compared to control.^[115] 

Spirulina may also benefit people with type 2 diabetes through inhibiting NADPH oxidase, which mediates the lipotoxicity of pancreatic beta-cells (that secrete insulin).^[21] 

Spirulina may help people with type 2 diabetes improve their glycemic control, but research is lacking.

8.1. Mechanisms

In a mouse model of metabolic syndrome, spirulina has been noted to reduce adipose tissue macrophage infiltration^[116] (macrophages in visceral fat tend to deposit themselves and secrete inflammatory cytokines^[117] which may exacerbate symptoms of metabolic syndrome^[118]) which appears to be a consequence of NADPH oxidase inhibition.^[118]

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

8.2. Interventions

100mg/kg Phycocyanin has been noted to reduce body weight in KKAy mice (genetically obese, hyperglycemic, and insulin resistant^[119]) associated with a reduction in food consumption over 21 days.^[120] 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).^[116]

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

9.1. 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,^[121] while the mechanisms of Spirulina-mediated immune potentiation appear to be mediated through TLR2 receptors, of which lipoproteins are agonists of;^[122] 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.^[123]

Inhibition of NF-kB has been noted elsewhere in both macrophages and splenocytes at 100μg/mL of the lipid extract.^[124]

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,^[9] which may draw confusion as this is also a patented name for a Spirulina product.^[121][125] 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.^[126]

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^[127][128]) and incubation with activated macrophages (via LPS) with C-phycocyanin can result in macrophage apoptosis via COX-2 inhibition (which is induced by LPS).^[129] The inhibitory potential of C-phycocyanin is potent with an IC₅₀ value of 180nM,^[130] 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.^[130] 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).^[130] The inhibitory potential of Phycocyanin is reduced to 9.7uM when the molecule itself is reduced (after accepting electrons, its anti-oxidant mechanism).^[130]

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).^[131]

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.^[132]

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

9.2. 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.^[121] Enhanced NK cell cytotoxicity (function) has been noted elsewhere with a Spirulina hot water extract.^[133]

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.^[134] 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.^[134]

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.^[134] Although TLR3-TICAM-1 can induce natural killer cell activation,^[135] TICAM-1^-/- mice do not appear to reduce the efficacy of Spirulina.^[134]

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

9.3. 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.^[136]

Lower doses (25-100mg/kg) are associated with significantly attenuated MPO induction (by alloxan), but not abolishment.^[137]

9.4. 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.^[138] 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.^[138] 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^[139] 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.^[139] 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.^[140] Protective effects were seen via histology, with 400mg/kg outperforming 100mg/kg and the reference drug being most effective.^[140]

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)

9.5. 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.^[141] 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.^[141] 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.^[142]

9.6. 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.^[143] TNF-α also trended to decline in both groups, and MCP-1 in females.^[143] 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.^[121][133]

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.^[137]

10.1. 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.^[144] 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).^[144]

10.2. 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.^[145] MDA, plasma Vitamin C, and intrinsic anti-oxidant enzymes were assessed.^[145]

11.1. 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.^[52]

11.2. 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.^[116]

12.1. 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.^[146] 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).^[146]

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.^[147]

12.2. 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,^[134] although other studies note reduction in tumor size and do not draw a link between said observation and NK cells.^[148]

12.3. 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.^[149]

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

12.4. 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.^[150]

12.5. 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,^[151] which tends to be increased in colon cancer cells.^[127] Many studies pair C-Phycocyanin with Piroxicam, which is a nonselective COX1/2 inhibitor, and the benefits appear additive.^{[128][152][153]}

Daily injections of 200mg/kg C-Phycocyanin can normalize Akt/PI3k activation and concurrently raise PTEN and GSK-3β activation,^[128] 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%)^[153] and reduced the amount of abberant crypt foci (indicative of polyp formation) by 65% in isolation, and 75% with Piroxicam.^[153] 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).^[152]

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.^[128]

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

13.1. 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.^[154] No significant differences were observed in the Actin protein component.^[154]

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

13.2. 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.^[155] 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

13.3. 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.^[156] 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%).^[156] 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.^[156] The only other study to measure lactate was at complete rest, and noted a non-significant trend to increase in runners.^[107]

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%).^[157]

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

13.4. 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.^[158]

14.1. 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.^[159]

15.1. 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.^[160] Protective effects on the liver from toxins have also been established against D-galactosamine and Acetominophen with 3-9% dietary Spirulina in rats.^[161]

15.2. 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.^[162] 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%.^[163]

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.^[160] 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.^[136]

15.3. 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.^[164] This hypothesis is based on suppression of stellate cell proliferation by activation of the ERb receptor (via one of the soy isoflavones Genistein^[165] and in part estrogen itself^[166]) 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.^[167][168]

15.4. Steatohepatitis (Fatty Liver)

Spirulina has the ability to reduce fatty liver (steatohepatitis) in various animal models, including fructose-induced obese rats,^[162], MSG-induced obese rats (where cerebral injections of MSG into newborn rats induces fatty liver via overeating^[169]),^[116] choline-deficient high fat diet injected with a pro-oxidant (2-6g/kg Spirulina).^[136]

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,^[116] 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),^[170]

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.^[171]

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%.^[172] 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).^[172]

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

15.5. 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.^[173]

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.^[174] 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.^[174] Responders had low baseline viremia. Another study on HIV failed to notice any benefit to abnormal liver enzymes associated with Spirulina^[175] 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%).^[176] 

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

15.6. 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.^[177] Platelets were unchanged over 12 weeks, and white blood cells increased significantly at 6 weeks in time; high variability noted in this study.^[177]

Spirulina may aid anemic symptoms, but evidence is preliminary

16.1. 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.^[178] 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.^[178]

16.2. 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^[179]), cisplatin (50mg/kg C-Phycocyanin),^[180][181] cyclophosphamide (1,000mg/kg of spirulina),^[182] 4-nitroquinoline-1-oxide (500mg/kg Spirulina),^[183] and Gentamycin.^[184] 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.^[185]

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

16.3. Lungs

The fibrotic effects of paraquat toxicity can be alleviated with 50mg/kg C-Phycocyanin in rats.^[186]

16.4. 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.^[52] 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%).^[52]

17.1. 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.^[147] Both were effective in reducing pathology associated with aflatoxin infection as well, with minor differences and little additive effects.^[147]

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

17.2. NT-020

NT-020 is a combination of polyphenols from blueberry, green tea catechins, carnosine (from beta-alanine) and Vitamin D^[187][188] 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^[189][190] in a synergistic manner itself^[187] with all bioactives being somewhat active (hypothesized to be secondary to reducing oxidative stress^[187]).

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)