Spirulina

    Written by:
    Wyatt Brown, Katie Jantz

    Fact-checked

    by:

    Nick Milazzo
    Last Updated: March 5, 2024

    Spirulina, commonly known as “blue-green algae”, is a nontoxic cyanobacterium that is rich in various nutrients and bioactive pigments and polyphenols. Spirulina contains many antioxidant compounds and could have beneficial cardiometabolic effects.

    What is spirulina?

    Spirulina (Arthrospira) is a non-toxic blue-green microalgae whose name is inspired by its spiral shape. Spirulina naturally thrives in warm, high-salt, alkaline (high pH) lakes. While it was originally believed to be a plant due to its photosynthetic capabilities, spirulina is now recognized as a type of cyanobacteria.[4] For commercial use, spirulina is usually cultivated in controlled environments and subsequently dried and pulverized.[5] There are several species of spirulina, but Arthrospira platensis is the one most frequently used in research and dietary supplements.[6]

    Spirulina is often touted as a “superfood” thanks to its impressive nutritional content, which includes proteins, essential amino acids, polyunsaturated fatty acids, vitamins, minerals, and various other bioactive compounds like carotenoids, chlorophyll, and phycocyanin. Accordingly, it has been used in a variety of contexts, ranging from undernourished populations to astronauts on space missions.[4][7]

    How has spirulina been used traditionally?

    What are spirulina’s main benefits?

    In vitro and animal research have suggested far-reaching benefits of spirulina, including antioxidant, anti-inflammatory, neuroprotective, anti-cancer, anti-viral, immune-modulating, hypoglycemic (blood-sugar-lowering), and cardioprotective properties.[1] However, only a few of these effects have been observed in human clinical trials.

    Clinical trials suggest that people who supplement with spirulina may see small but positive effects on various aspects of their cardiometabolic health, including improved lipid profiles,[1][8] decreased blood pressure (particularly in those with high blood pressure),[9] small reductions in body weight,[10][11] and decreased fasting glucose.[8][12]

    Spirulina is often touted as a potent antioxidant and anti-inflammatory supplement. While this certainly is the case in pre-clinical research, human clinical trials have been mixed. Spirulina might increase total antioxidant capacity and superoxide dismutase activity, but no clear effects on inflammation have been found.[13][14]

    Is spirulina a good supplement for someone following a plant-based diet?Does spirulina improve exercise performance or recovery?Does spirulina improve allergies?Does spirulina affect the risk or progression of cancer?Does spirulina affect the gut microbiome?Does spirulina improve anemia?Does spirulina improve nonalcoholic fatty liver disease?

    What are spirulina’s main drawbacks?

    Spirulina is generally considered to be safe and well-tolerated. The most commonly reported side effects include gastrointestinal upset (e.g., abdominal cramps, diarrhea, nausea, vomiting), fatigue, dizziness, headache, and skin irritation (e.g., itching, rash).[15]

    There have been several case reports of more severe side effects with spirulina supplementation. These include rhabdomyolysis (a severe type of muscle breakdown),[16] anaphylaxis (a life-threatening allergic reaction),[17][18] liver toxicity,[19] and the initiation or exacerbation of autoimmune skin conditions.[20][21]

    Although this has not been thoroughly investigated, spirulina may inhibit some cytochrome P450 enzymes, namely CYP1A2 and CYP2E1, which could lead to drug interactions.[22]

    Manufacturing practices and growth environments can influence the quality and safety of spirulina supplements. First, spirulina can accumulate heavy metals from its environment, raising the concern of contamination.[23] One study that checked 25 brands of spirulina for mercury, nickel, and platinum found that none contained these heavy metals beyond acceptable levels,[24] but choosing a spirulina supplement that is tested for heavy metals should still be a consideration. Second, contamination with other species of cyanobacteria could introduce potentially toxic compounds like microcystins.[25]

    How does spirulina work?

    Spirulina contains an abundance of bioactive compounds, including pigments, polyphenols, peptides, fatty acids, complex carbohydrates, vitamins, and minerals, which makes its mechanism of action fairly complicated and still incompletely understood. Phycocyanin, a blue-colored pigment that is structurally similar to bilirubin, is the most abundant protein in spirulina and is suggested to be the major active compound.[26]

    The antioxidant and anti-inflammatory properties of spirulina are the most thoroughly studied and likely arise from a variety of compounds including phycocyanin, carotenoids, chlorophyll, and vitamin E. Spirulina may increase the activity of antioxidant enzymes (e.g., superoxide dismutase), prevent lipid peroxidation, reduce NF-κB activity, and inhibit enzymes involved in the generation of reactive oxygen species and inflammatory compounds — nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and cyclooxygenase-2 (COX-2), respectively.[26][14][27]

    Spirulina may enhance cardiometabolic health through various mechanisms. It could potentially lower blood pressure by increasing nitric oxide production, thereby inhibiting angiotensin I converting enzyme, and/or simply due to its high potassium content (~18 mg per gram).[9][4] Moreover, spirulina may influence lipid metabolism, reduce the digestion and absorption of dietary fats and carbohydrates, promote cholesterol excretion, increase satiety, and stimulate insulin secretion.[28][29][1][30]

    What are other names for Spirulina?

    Note that Spirulina is also known as:

    • Arthrospira maxima
    • Arthrospira platensis
    • Arthrospira fusiformis
    • Arthrospira

    Spirulina should not be confused with:

    Dosage information

    Spirulina is usually dosed in the range of 2 to 10 grams daily in whole powder or capsule form. Extracts are sometimes used, but they are less thoroughly studied and do not contain the full array of compounds found in dried spirulina.

    Higher doses of spirulina, in the range of 4 to 10 grams daily, appear to be most effective for improving lipid profiles and possibly for reducing fatigue during endurance exercise.[1][2]

    A lower dose of 2 grams daily may help reduce symptoms of allergic rhinitis.[3]

    Frequently asked questions

    What is spirulina?

    Spirulina (Arthrospira) is a non-toxic blue-green microalgae whose name is inspired by its spiral shape. Spirulina naturally thrives in warm, high-salt, alkaline (high pH) lakes. While it was originally believed to be a plant due to its photosynthetic capabilities, spirulina is now recognized as a type of cyanobacteria.[4] For commercial use, spirulina is usually cultivated in controlled environments and subsequently dried and pulverized.[5] There are several species of spirulina, but Arthrospira platensis is the one most frequently used in research and dietary supplements.[6]

    Spirulina is often touted as a “superfood” thanks to its impressive nutritional content, which includes proteins, essential amino acids, polyunsaturated fatty acids, vitamins, minerals, and various other bioactive compounds like carotenoids, chlorophyll, and phycocyanin. Accordingly, it has been used in a variety of contexts, ranging from undernourished populations to astronauts on space missions.[4][7]

    How has spirulina been used traditionally?

    Records show that spirulina was used traditionally as a food by the Aztecs in Mexico and has been used by the Kanembu people of North Africa since at least the 16th century. In Africa, spirulina — locally called dihé — is harvested from various alkaline lakes surrounding Lake Chad. Similarly, in Mexico before the Spanish conquest, spirulina — locally called tecuitlatl — was harvested from Lake Texcoco, where it grew abundantly. In both cases, the spirulina is gathered from the lakes and left to try in the sun, after which it can be broken into small pieces to be sold as food.[26][31][32]

    What are spirulina’s main benefits?

    In vitro and animal research have suggested far-reaching benefits of spirulina, including antioxidant, anti-inflammatory, neuroprotective, anti-cancer, anti-viral, immune-modulating, hypoglycemic (blood-sugar-lowering), and cardioprotective properties.[1] However, only a few of these effects have been observed in human clinical trials.

    Clinical trials suggest that people who supplement with spirulina may see small but positive effects on various aspects of their cardiometabolic health, including improved lipid profiles,[1][8] decreased blood pressure (particularly in those with high blood pressure),[9] small reductions in body weight,[10][11] and decreased fasting glucose.[8][12]

    Spirulina is often touted as a potent antioxidant and anti-inflammatory supplement. While this certainly is the case in pre-clinical research, human clinical trials have been mixed. Spirulina might increase total antioxidant capacity and superoxide dismutase activity, but no clear effects on inflammation have been found.[13][14]

    Is spirulina a good supplement for someone following a plant-based diet?

    Spirulina is sometimes promoted for people following a plant-based diet because of its protein and vitamin B12 content. While it may have a role in this context, the value is often overstated.

    Based on its dry weight, spirulina is about 60 to 75% protein (~65 g per 100 g dried spirulina) and contains all of the essential amino acids.[33] This is notable for a protein source that is not animal-based, but spirulina is usually only dosed up to 10 grams daily, which would provide 7.5 grams of protein at best. While this might help someone reach their protein goals, it only fulfills a fraction of daily protein requirements.

    On average, a 10-gram dose of spirulina might contain around 20 micrograms of vitamin B12.[4] However, the majority of vitamin B12 in spirulina is actually a type of pseudovitamin B12 that is not readily usable by the human body.[34] One study found that 83% of the vitamin B12 in spirulina was in the pseudovitamin form, which would reduce the usable amount of vitamin B12 in a 10-gram dose from 20 micrograms to 3.4 micrograms. While 3.4 micrograms is a much smaller dose than that normally found in vitamin B12 supplements, it technically does meet the Recommended Daily Allowances (RDAs) for all age and sex groups.[35]

    Does spirulina improve exercise performance or recovery?

    Spirulina may have some beneficial effects on exercise performance, but current evidence is mixed and inconclusive.

    Preliminary research suggests that spirulina may have a positive effect on endurance training (e.g., running, cycling) by lowering fatigue and increasing power output, possibly through reductions in oxidative stress and increases in hemoglobin levels and oxygen uptake.[36][37][38][2]

    In terms of recovery, the majority of research suggests that spirulina has no impact on post-exercise muscle recovery, including delayed onset muscle soreness.[2] However, in athletes with an insufficient intake of dietary antioxidants, spirulina may reduce muscle oxidative damage and accelerate recovery.[38][2]

    While the antioxidant effects of spirulina in clinical trials are generally mixed, it’s also important to consider that antioxidant supplementation during or after exercise may blunt the body's natural responses required for muscle adaptation and growth.[39]

    Does spirulina improve allergies?

    Spirulina has shown some promise for reducing symptoms of allergic rhinitis, but research is still at an early stage.

    A few studies have found that compared to a placebo, spirulina reduced symptoms of allergic rhinitis.[40][41] Interestingly, a randomized controlled trial found that spirulina supplementation given daily for two months was as effective as cetirizine — a commonly-used allergy medication — at reducing symptoms of nasal itching and sneezing and more effective than cetirizine at reducing rhinorrhea (runny nose) and nasal congestion.[3]

    This effect may be due to how spirulina interacts with the immune system. More specifically, spirulina may reduce levels of interleukin 4 and prevent the release of histamine from mast cells.[42][3][43][44]

    Does spirulina affect the risk or progression of cancer?

    Spirulina has demonstrated anticancer properties in in vitro and animal studies, but human clinical trials are scarce.

    Spirulina contains several compounds that have individually been found to have anticancer properties, and of these, phycocyanin appears to have the greatest potential. Phycocyanin extracted from spirulina has been shown in pre-clinical research to induce cell death (apoptosis) in a variety of cancer cell lines and prevent the formation of new blood vessels (angiogenesis), effectively inhibiting the proliferation of cancer cells.[45]

    Additionally, some research suggests that spirulina may enhance natural killer cell activity, which could have an antitumor effect.[46][47] Several clinical trials suggest that spirulina supplementation may reverse precancerous lesions in the mouth.[48][49][50][51]

    Does spirulina affect the gut microbiome?

    Spirulina contains compounds with antibacterial properties, as well as complex carbohydrates and polyphenols capable of stimulating the growth of certain microbes. Preclinical research suggests that spirulina may inhibit the growth of some potentially pathogenic microorganisms (e.g., Escherichia coli, Staphylococcus aureus, Candida albicans) while supporting the growth of microorganisms generally thought to be beneficial (e.g., those in the Lactobacillus and Bifidobacteria genera).[6]

    While this suggests that spirulina has the potential to beneficially impact the gut microbiome, there is currently no research exploring this in humans.

    Does spirulina improve anemia?

    Spirulina supplementation has been shown in a variety of populations to improve markers of iron deficiency anemia, including increased levels of hemoglobin, a higher red blood cell count, and an increased hematocrit.[52][53][54][37][55]

    This effect could relate to spirulina’s highly bioavailable iron (although there are only ~5 mg of iron per 10 grams of dried spirulina),[4] but the predominant protein in spirulina, phycocyanin, may also stimulate red blood cell production.[56]

    There currently isn’t enough research to suggest that spirulina might be a replacement for standard anemia treatments such as iron supplementation. Additionally, the nutritional content of spirulina can vary depending on the cultivation and processing techniques used, which could alter its effectiveness for anemia.[27]

    Does spirulina improve nonalcoholic fatty liver disease?

    In animal studies, spirulina has demonstrated promise for the management or prevention of nonalcoholic fatty liver disease (NAFLD), but more research in humans is needed to confirm this effect.

    In mice, spirulina has demonstrated the ability to both prevent and reduce the incidence of fatty liver in mouse models of NAFLD, although these studies have generally used much higher doses of spirulina than are recommended for humans.[57][58][59] In people with NAFLD, both a series of case studies including three people and an uncontrolled study including fifteen people found that spirulina supplementation significantly reduced liver enzymes. Nevertheless, ultrasound assessments didn’t consistently find improvements in NAFLD.[60][61]

    What are spirulina’s main drawbacks?

    Spirulina is generally considered to be safe and well-tolerated. The most commonly reported side effects include gastrointestinal upset (e.g., abdominal cramps, diarrhea, nausea, vomiting), fatigue, dizziness, headache, and skin irritation (e.g., itching, rash).[15]

    There have been several case reports of more severe side effects with spirulina supplementation. These include rhabdomyolysis (a severe type of muscle breakdown),[16] anaphylaxis (a life-threatening allergic reaction),[17][18] liver toxicity,[19] and the initiation or exacerbation of autoimmune skin conditions.[20][21]

    Although this has not been thoroughly investigated, spirulina may inhibit some cytochrome P450 enzymes, namely CYP1A2 and CYP2E1, which could lead to drug interactions.[22]

    Manufacturing practices and growth environments can influence the quality and safety of spirulina supplements. First, spirulina can accumulate heavy metals from its environment, raising the concern of contamination.[23] One study that checked 25 brands of spirulina for mercury, nickel, and platinum found that none contained these heavy metals beyond acceptable levels,[24] but choosing a spirulina supplement that is tested for heavy metals should still be a consideration. Second, contamination with other species of cyanobacteria could introduce potentially toxic compounds like microcystins.[25]

    How does spirulina work?

    Spirulina contains an abundance of bioactive compounds, including pigments, polyphenols, peptides, fatty acids, complex carbohydrates, vitamins, and minerals, which makes its mechanism of action fairly complicated and still incompletely understood. Phycocyanin, a blue-colored pigment that is structurally similar to bilirubin, is the most abundant protein in spirulina and is suggested to be the major active compound.[26]

    The antioxidant and anti-inflammatory properties of spirulina are the most thoroughly studied and likely arise from a variety of compounds including phycocyanin, carotenoids, chlorophyll, and vitamin E. Spirulina may increase the activity of antioxidant enzymes (e.g., superoxide dismutase), prevent lipid peroxidation, reduce NF-κB activity, and inhibit enzymes involved in the generation of reactive oxygen species and inflammatory compounds — nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and cyclooxygenase-2 (COX-2), respectively.[26][14][27]

    Spirulina may enhance cardiometabolic health through various mechanisms. It could potentially lower blood pressure by increasing nitric oxide production, thereby inhibiting angiotensin I converting enzyme, and/or simply due to its high potassium content (~18 mg per gram).[9][4] Moreover, spirulina may influence lipid metabolism, reduce the digestion and absorption of dietary fats and carbohydrates, promote cholesterol excretion, increase satiety, and stimulate insulin secretion.[28][29][1][30]

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