Spirulina: The Super Food

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What is Spirulina?

Spirulina is a type of blue-green algae (specifically a photosynthetic cyanobacterium) that is rich in protein, vitamins, minerals, lipids and phytochemicals. Spirulina is a human and animal food or nutritional supplement made primarily from two species of cyanobacteria: Arthrospira platensis and Arthrospira maxima. The name, spirulina, derives from the spiral or helical nature of its filaments. The maxima and platensis species were once classified in the genus Spirulina. There is now agreement that they are in fact Arthrospira; nevertheless, and somewhat confusingly, the older term Spirulina remains in use for historical reasons. There are several cultivated species such as S. fusiformis, S. laxissima, S. subsalsa, S. lonar, and S. labyrinthiformis in addition to the aforementioned maxima and platensis species. The maxima and platensis species are the most widely exploited for nutritional and therapeutic aspects.

Spirulina is a nourishing food concentrate as it is highly rich in protein (60–70%), vitamins (4%), essential fatty acids and antioxidants. Although Spirulina is often marketed as an excellent source of protein, it is no better in this regard than milk or meat, and is approximately 30 times more expensive per gram of protein. However, for persons following a vegetarian or vegan dietary lifestyle, Spirulina is one of the best sources of protein because of all the additional nutritional benefits. Spirulina is a rich source of the essential fatty acids linoleic acid (LA) and alpha-linolenic acid (ALA), as well as numerous other highly important fatty acids including palmitic acid, γ-linolenic acid (GLA), stearidonic acid (SDA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA). The nutritional benefits of EPA and DHA (omega-3 polyunsaturated fatty acids, PUFAs) are discussed in the PUFAs page.

Spirulina contains numerous phytochemicals such as phycobiliproteins, the most important being c-phycocyanin and allophycocyanin. Spirulina contains high amounts of the metabolically important branched-chain amino acids leucine, valine and isoleucine which are critical for muscle protein production in humans. In addition to the branched-chain amino acids Spirulina contains all of the essential amin acids required for human protein production.

Spirulina also contains numerous minerals such as potassium, calcium, chromium, copper, iron, magnesium, manganese, phosphorus, selenium, sodium and zinc. Spirulina also contains numerous vitamins such as B-complex vitamins (B1: thiamine; B2: riboflavin; B3: niacin; B6: pyridoxine), folic acid, vitamin A, vitamin C, vitamin D and vitamin E. However, Spirulina is not considered to be a reliable source of bioavailable vitamin B12. The standard B12 assay, using Lactobacillus leichmannii, shows Spirulina to be a minimal source of bioavailable vitamin B12. Spirulina supplements contain predominantly pseudovitamin B12, which is biologically inactive in humans. Companies which grow and market spirulina have claimed it to be a significant source of B12 on the basis of alternate, unpublished assays, although their claims are not accepted by independent scientific organizations.

Recently, attention has been placed on the antioxidant potential of Spirulina. Indeed, many of the chemical components of Spirulina, such as beta-carotene, zeaxanthin, chlorophyll-a, xanthophyll, echinenone, myxoxanthophyll, canthaxanthin, diatoxanthin, 3'-hydroxyechinenone, beta-cryptoxanthin and oscillaxanthin, plus the phycobiliproteins mentioned above (c-phycocyanin and allophycocyanin) exhibit antioxidant properties. Spirulina exhibits therapeutic functions such as antioxidant, anti-bacterial, antiviral, anticancer, anti-inflammatory, anti-allergic and anti-diabetic and plethora of beneficial functions. Spirulina consumption appears to promote the growth of intestinal micro flora as well.

Spirulina, like any blue-green algae, can be contaminated with toxic substances called microcystins, and can also absorb heavy metals if any are present in the water where it is grown. For these reasons, it is important to buy Spirulina from a trusted source or manufacturer. Cell culture and animal studies suggest Spirulina may boost the immune system, help protect against allergic reactions, and have antiviral and anticancer properties. However, there is no proof that Spirulina has these, or any, benefits in humans. As a dietary supplement Spirulina is available in pill or powder form, or as flakes. Most of the Spirulina consumed in the United States is grown in a laboratory. There are many different spirulina species, only some of which are identified on labels of commercially available products. Spirulina maxima (cultivated in Mexico) and Spirulina platensis (cultivated in California) are the most popular.

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Therapeutic Uses of Spirulina

Spirulina as an Antioxidant

Several studies have demonstrated that Spirulina supplements possess a significant amount of antioxidant activity both in vitro and in vivo. The phenolic compounds responsible for the antioxidant properties of the A. maxima extracts were organic acids (caffeic, chlorogenic, quimic, salicylic, synaptic and trans-cinnnamic) which acted individually and synergistically.  The antioxidant activity of the phycobiliproteins, c-phycocyanin and allophycocyanin, present in Spirulina biomass have also been shown to quite high. An alcohol extract of Spirulina has been shown to inhibit lipid peroxidation more significantly than other chemical antioxidants such as α-tocopherol and β-carotene. The water extract of Spirulina has also been shown to have more antioxidant effect than gallic acid and chlorogenic acid. Phycocyanin from Spriulina also inhibits liver microsomal lipid peroxidation. Hot water extracts of Spirulina demonstrate significant capacity to scavenge hydroxyl radicals (the most highly reactive oxygen radical) but have no effect on superoxide radicals.

Spirulina and Reduction in Diabetes Symptoms

Spirulina has been shown to possess antihyperglycemic and antihyperlipidemic properties in experimental models. In patients with type-2 diabetes, Spirulina supplementation results in lowered fasting blood glucose, postprandial glucose and reduction in the glycosylated hemoglobin (HbA1c). The aqueous extract of A. maxima is highly effective in alleviating the abnormalities of carbohydrate and lipid metabolism observed in laboratory animals fed excess fructose. Treatment of diabetic rats with Spirulina increased hexokinase (increases glucose metabolism) activity and decreased glucose-6-phosphatase activity (liver enzyme involved in glucose synthesis). In studies aimed at measuring the effect of Spirulina on glucose levels in diabetic rodents, the water soluble fraction was found to be effective in lowering serum glucose levels at fasting as well as in response to glucose loading. S. maxima exhibits hypolipidemic effects, especially on triacylglycerols (TAG) and  LDL. The elevation of total cholesterol, LDL and VLDL cholesterol and phospholipids that is seen in the blood of experimental animals fed a high cholesterol diet is significantly reduced when the experimental diet is supplemented with 16% Spirulina. The fall in HDL cholesterol caused by the high cholesterol diet is also prevented in mice fed with Spirulina. Adipohepatosis induced by a high fat and high cholesterol diet is also rapidly reduced when mice are shifted from the high fat, high cholesterol diet to a standard chow supplemented with Spirulina. Liver levels of TAG and phospholipids are also observed to decline when rats are fed a diet supplemented with 5% Spirulina.

Modulation of Inflammation by Spirulina

Spirulina has been shown to have potent effects at the level of modulating the immune system. In studies on mice, hamsters, chickens, turkeys, cats and fish, Spirulina consistently improved immune system function. Spirulina not only stimulates the immune system, it actually enhances the body’s ability to generate new blood cells. The spleen and thymus glands show enhanced function, macrophages, T-cells and natural killer (NK) cells exhibit enhanced activity following Spirulina administration. Feeding of even small amounts of Spirulina to mice results in immunomodulatory actions. The c-phycocyanin extract of Spirulina exhibits some of the highest antiinflammatory activity in experimental models. The anti-inflammatory effects of c-phycocyanin appears to be a result of c-phycocyanin inhibiting the formation of leukotriene B4 (LTB4), a potent pro-inflammatory metabolite of arachidonic acid (for information on arachidonic acid metabolites and inflammation visit the Eicosanoids page at The Medical Biochemistry Page). C-phycocyanin is a free radical scavenger and has significant hepatoprotective effects.

Anti-cancer Activities of Spirulina

Spirulina may offer some degree of protection against certain forms of cancer through its effect on the immune system. In addition, Spirulina may exert anticancer activity through a direct effect on the repair of DNA, as well as through antioxidant protection from reactive oxygen species (ROS) generated during normal or abnormal metabolism and from toxic substances in the environment. One human study on the effect of Spirulina on chemoprevention of cancer involved oral leukoplakia (a precancerous lesion). Discontinuation of Spirulina supplementation, resulted in recurrent lesions in almost half of the subjects in the study. Ingestion of an extract of Spirulina has been shown to inhibit chemically induced carcinogenesis in hamster buccal pouches. Several studies have attributed the anti-cancer effect of Spirulina to its carotenoids since β-carotene had previously been shown to have an effect similar to that of an algal extract. More recent studies have shown that the calcium spirulan (Ca-Sp; a sulfated polysaccharide of blue-green alga) of Spirulina is responsible for inhibition of tumor invasion and metastasis. Both the in vivo and in vitro effects of Ca-Sp suggest that the intravenous administration of Ca-Sp reduces the lung metastasis of melanoma cells by inhibiting the tumor invasion of the basement membrane. Of major interest to ongoing research in inflammation as well as breast cancer is the finding that c-phycocyanin selectively inhibits cyclooxygenase-2 (COX-2), but has no effect on COX-1. The COX enzymes, which are involved in prostaglandin synthesis, are over expressed in many breast cancer cells. The inhibition of COX-2 by Spirulina has been shown to result in reduced tumor growth and inhibition of angiogenesis.

Spirulina as a Probiotic Stimulant

Spirulina acts as a functional food feeding beneficial intestinal flora, especially Lactobacillus and Bifidus. Maintaining a healthy population of these bacteria in the intestine reduces potential problems from opportunistic pathogens like E.coli and Candida albicans. In studies on rats, a diet supplemented with 5% Spirulina for 100 days resulted in an increase in the weight of the caecum, an increase in the amount of Lactobacillus, and an increase in the amount of vitamin B1 inside the caecum. The increased B1 did not come from the Spirulina, thus the increase was due to improved overall B1 absorption. This particular study suggests that eating Spirulina results in increases Lactobacillus and in turn may increase efficient absorption of vitamin B1 and other vitamins from the entire diet. Additional studues have demonstrated that Spirulina in the diet exerts a stimulatory effect on lactic acid bacteria including Lactobacillus lactis, Streptococcus thermophilus, L. casei, L. acidophilus and L. bulgaricus. Spirulina also exhibits potent antibacterial activities against pathogenic bacteria. Administration of Spirulina via injection to laboratory animals results in heightened clearance of E.coli and Staphylococcus aureus, both pathogenic bacteria. In addition 30 minutes after injection the bacterial counts were almost negligible in the blood. This heightened bacterial clearance is attributed to the immunomodulating effects of Spirulina.

Anti-viral Activities of Spirulina

Spirulina has been shown to have important anti-viral activity. When administered at a low concentration it results in reduced viral replication whereas, at higher concentrations it blocks replication. Of significance to use in humans is that Spirulina extracts are nontoxic to human cells at concentrations that result in inhibition of viral replication indicating that the extracts do not interfere with DNA replication in human tissues. A water soluble extract of Spirulina has been shown to inhibit viral cell-penetration and replication of the Herpes Simplex Virus Type 1 (HSV-1) in cultured HeLa cells in a dose dependent manner. The Spirulina extract inhibits viral protein synthesis without suppressing host cell functions. When Spirulina fed hamsters are challenged with the HSV-1 they have prolonged survival times and higher overall rates of survival. The anti-viral activity is attributed to Ca-Sp, which has been shown to inhibit replication of many enveloped viruses by inhibition of viral penetration into target cells without host toxicity. Ca-Sp has been shown to exhibit activity against human cytomegalovirus, measles virus, mumps virus, influenza A virus, human immunodeficiency virus (HIV-1) as well as HSV-1.

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Supporting Research

Kulshreshtha A, Zacharia AJ, Jarouliya U, Bhadauriya P, Prasad GB and Bisen PS. 2008. Spirulina in health care management. Curr. Pharm. Biotechnol. 9(5):400-405.

Deng R and Chow TJ. 2010. Hypolipidemic, antioxidant, and antiinflammatory activities of microalgae Spirulina. Cardiovasc Ther. 28(4):e33-45

Karkos PD, Leong SC, Karkos CD, Sivaji N and Assimakopoulos DA. 2011. Spirulina in Clinical Practice: Evidence-Based Human Applications. Evid. Based Complement. Alternat. Med.

Lee, EH, Park, J-E, Choi, Y-J, Huh, K-B and Kim, W-Y. 2008 A randomized study to establish the effects of spirulina in type 2 diabetes mellitus patients. Nutrition Research and Practice 2(4):295-300

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Last modified: September 7, 2020