Spirulina refers to various species of blue-green algae found naturally in lakes and grown commercially. It is used as a food colouring and is taken orally as a nutritional supplement in tablet, capsule or dried powder form. It is claimed to have immune-stimulating effects and to be beneficial in a wide range of diseases including cardiovascular disease, diabetes, viral infections and cancer.
Studies located included an RCT conducted in China assessing effects on immune function and myelosuppression which reported beneficial effects but not details of the chemotherapy used. A trial in India assessed effects on prevention of oral cancer in a group of tobacco chewers. Several preliminary studies in healthy individuals assessing effects on various biomarkers also reported positive effects but were very small.
Anti-tumour treatment
Tumour burden or response: No trials were identified.
Supportive cancer care
Myelosuppression and immune function: One RCT in 100 patients with various malignant tumours found that spirulina reduced myelosuppression and improved immune function after chemotherapy. This resulted in less chemotherapy modification but regimens used were not reported.
Cancer prevention
Oral cancer: One placebo-controlled trial in India in 1995 suggested beneficial effects of Spirulina dietary supplements but these results have not been replicated since.
Various biomarkers: Pilot studies report effects including enhanced natural killer cell activity, T-cell proliferation or interferon production but studies were very small (< 12 patients) so the results can only be considered as preliminary.
Few adverse effects have been reported with spirulina products and it is generally well-tolerated. Some blue-algae products have been found to be contaminated with hepatotoxic microcystins which can cause serious adverse effects above tolerable levels. Reliable evidence on safety in pregnancy and breast-feeding is not available.
Citation
Karen Pilkington, CAM Cancer Collaboration. Spirulina (blue-green algae) [online document], Apr 28, 2023.
Document history
Next update due April 2026.
Last updated in April 2023 by Karen Pilkington.
Summary first published in April 2013, authored by Karen Pilkington.
Description and background
Spirulina is a microscopic, filamentous, blue-green algae used as a nutritional supplement. Its name derived from the fact that the filaments are spiral (Khan 2005a; Karkos 2011).
Spirulina was originally harvested from lakes in parts of Africa and Mexico, dried and used as a food (Ciferrri 1987). It was reportedly used during the Aztec civilisation (Karkos 2011). It still forms an important part of the diet in several parts of the world as a source of protein and because it lacks cellulose cell walls so is easily digested (Karkos 2011). It gained prominence more recently after it was used as a dietary supplement for astronauts on space missions (Clark 2005).
Commercially, spirulina species are now generally grown under controlled conditions (NMD 2022). In North America, the two most popular species, Spirulina maxima and Spirulina platensis, are cultivated in Mexico and California respectively (Drugs 2022). It is also cultivated in Thailand, India, Japan and China (Khan 2005a).
Spirulina was not among those supplements reported in European surveys on the use of complementary medicine by breast, colorectal or lung cancer patients Molassiotis 2005a; Molassiotis 2005b; Molassiotis 2006). Therefore, the prevalence of use in Europe is unclear. It is widely used by cancer populations in South East Asia with surveys revealing it is one of the most frequently used supplements (Hamidah 2019; Shaharudin 2011).
Scientific and other names
Scientific names:
Spirulina maxima; Spirulina platensis, Spirulina maxima, Spirulina pacifica (also known as Arthrospira platensis, Arthrospira maxima); Brand and common names: Blue Green Algae, Cyanobacteria, SBGA, Spiralyne, Spirulina Blue-Green Algae, Spiruline (Karkos 2011).
Ingredient and quality issues
The constituents of spirulina include protein (50-70%) including all essential amino-acids, essential fatty acids, polysaccharides, B vitamins particularly vitamin B12, beta-carotene and minerals particularly iron (Khan 2005a, Karkos 2011; NMD 2022).
Alleged indications
Blue-green algae as a group are used as nutritional supplements due their high protein and vitamin and iron content (NMD 2022). They are also used for promoting weight loss. Spirulina has been used as a general immunostimulant and it has been suggested that it could be taken to prevent and treat cancer and viral infections (MSKCC 2020).
A wide range of other uses have been proposed: these include the treatment of anxiety and depression, attention deficit hyperactivity disorder, cardiovascular disease including raised cholesterol levels, diabetes, fatigue, premenstrual syndrome (PMS), and the promotion of digestion and bowel health (NMD 2022). A review published in 2011 concluded that multiple studies on the efficacy of spirulina in several diseases had been conducted and it may have anticancer, antiviral and anti-allergic effects (Karkos 2011).
Application and dosage
Spirulina is taken orally, as capsules, tablets, powder or as flakes either dried or freeze-dried form (Drugs 2022). Varied doses have been used in clinical studies; a dose of 1g per day was used to treat oral leukoplakia (Mathew 1995) while 400mg/day of an enriched spirulina extract was used to enhance natural killer cell activity in healthy subjects (Nielsen 2010). Standard doses of 2 to 3g per day have been recommended by manufacturers for a range of conditions (Drugs 2022). Doses of up to 10 grams daily for up to 6 months have been used for various conditions (NMD 2022).
Mechanisms of action
Spirulina can be used simply as a protein supplements but it is also considered to have specific effects on the immune system although the potential mechanism of action on the immune system is not fully understood. Preliminary studies in healthy humans suggest that spirulina increases the production of the cytokines, tumour necrosis factor, interleukin (IL)-2, and interferon, and causes CD4+ T-helper cell proliferation (Hirahashi 2002; Lobner 2008).
It also appears to increase the activity and cytotoxicity of natural killer cells (Nielsen 2010). Animal studies have demonstrated chemoprotective effects when spirulina is given with various cytotoxic drugs (Bhattacharya 2012; Khan 2005b; Mohan 2006). Several animal studies have investigated the potential of spirulina to have a protective effect against toxicity related to various cytotoxic agents, such as doxorubicin-induced cardiotoxicity (Khan 2005b) and cisplatin-induced nephrotoxicity (Bhattacharya 2012; Mohan 2006). Beneficial effects have been reported although it is unclear if these findings will translate into clinical use.
Legal issues
Spirulina is widely available as a food and is found as an additive (food colouring) in many foodstuffs. A survey in 2007 revealed that the legal situation regarding spirulina varied across the 27 member states of the European Union, with many countries allowing use as a food supplement, but several restricting or prohibiting use as a food supplement or medicinal use (EAS 2020).
One systematic review of the potential anticancer effects of Arthrospira sp. included only vitro studies and in vivo studies in mice and rats (de Silva 2021). Other studies located included an RCT conducted in China assessing effects on immune function and myelosuppression which reported beneficial effects but not details of the chemotherapy used (Ge 2019). A trial in India assessed effects on prevention of oral cancer in a group of tobacco chewers. Several preliminary studies in healthy individuals assessing effects on various biomarkers also reported positive effects but were very small.
Anti-tumour treatment
Tumour burden or response: No trials were identified.
Supportive cancer care
Myelosuppression and immune function: One RCT in 100 patients with various malignant tumours found that spirulina reduced myelosuppression and improved immune function after chemotherapy. This resulted in less chemotherapy modification but regimens used were not reported.
Cancer prevention
Oral cancer: One placebo-controlled trial in India in 1995 suggested beneficial effects of Spirulina dietary supplements but these results have not been replicated since.
Various biomarkers: Three pilot studies report effects including enhanced natural killer cell activity, T-cell proliferation or interferon production but studies were very small (< 12 patients) so the results can only be considered as preliminary.
Description of included studies
Supportive cancer care
Spirulina (Arthrospira sp.) consumed during the first two cycles of four cycles of chemotherapy was compared against no such supplement in 100 patients with various solid tumours (Ge 2019). The patients were aged between 18 and 70 with a stage II/III/IV malignant tumour, with or without grade I/II bone marrow suppression after receiving chemotherapy and no prior radiotherapy. Spirulina was obtained from InM Wushenzhao Ecological Development Co., Ltd. and 3 capsules of 100 mg each administered 3 times daily with meals.
Myelosuppression and immune function were assessed after each cycle of chemotherapy, and adverse events throughout the study. Significantly lower rates of severe myelosuppression (P=0.034) and less modification of the chemotherapy regimen was necessary (P=0.012) in patients assigned spirulina. After four cycles of chemotherapy, the IgM level and number of CD8(+) T cells increased in the treatment group but decreased in the control group (P=0.004 for IgM; P=0.022 for CD8(+) T cells). The trial was randomised but few details are reported on the allocation process or why unequal numbers were recruited to the two groups. Chemotherapy regimens were not described although the latter were reported as well-matched. No mention is made of attrition during the study.
Cancer prevention
A clinical trial of 1g/day of Spirulina fusiformis for chemoprevention of oral cancer was reported in 1995 (Mathew 1995). The trial was conducted over the course of 12 months in pan tobacco chewers in Kerala, India who were suffering from oral leucoplakia (a pre-cancerous condition). Complete regression of lesions was observed in 45% (20 of 44 subjects) whose diet was supplemented with spirulina.
This compared favourably with those receiving placebo: only 3 of 43 (7%) showed a complete regression in lesions (p < 0.0001). The response appeared to be greater in those with homogeneous lesions. Increased serum concentrations of retinol or beta-carotene were not observed nor was toxicity reported. Sixty people received the spirulina but it appears that the control group was a group who had been randomised to the placebo arm of another study and there were some differences between groups at baseline.
Assessment of response was carried out by a physician and a dentist who were unaware of the allocated treatment group but it is unclear to what extent the spirulina and placebo capsules were well-matched. Only the results from those completing the study were included (44 and 43 respectively) in the final analysis. Muscular pain and headaches were reported by 7 and 5 patients taking spirulina and no adverse events were reported by those in the placebo group.
A spirulina product, which apparently has ‘enhanced activity’, was used in a pilot study in the USA in 10 healthy individuals After 7 days of the supplement (400mg per day), increased cytotoxic activity of natural killer cells was observed (Nielsen 2010). A separate placebo-controlled study was also conducted by the same authors. This study involved 11 healthy Danish participants who were randomised to receive 200mg spirulina, 400mg spirulina or placebo daily each for one week with 3.5 week washout periods between treatments Enhanced natural killer cell activity was again reported after 7 days treatment (Nielsen 2010).
Increased T-cell proliferation and interferon production has also been reported in studies in humans (Hirashi 2002; Lobner 2008). These studies all suffer from very small numbers of participants (maximum of 12) and were conducted in healthy subjects, therefore the results can only be considered as preliminary.
Adverse events
Few adverse effects are caused by good quality blue-green algae products (NMD 2022). Contamination has been reported of some spirulina products which will affect the products’ safety (see Warnings). Most frequent adverse effects are those affecting the gastrointestinal system (NMD 2022). A review of safety by the US Pharmacopeia Dietary Supplements Information Expert Committee considered a total of 31 adverse events reported in relation to spirulina (Marles 2011).
Side effects reported in clinical trials include gastro-intestinal problems such as diarrhoea and flatulence (NMD 2022). Headaches and general muscular aches were reported by some patients in one trial although it uncertain whether these were due to spirulina (Mathew 1995). One case of anaphylaxis (Petrus 2010) and one of acute rhabdomyolysis have also been reported (Mazokopakis 2008). The latter resolved after discontinuation of the supplement. Other individual cases of adverse effects including severe rashes, mild gum bleeding and bruising, raised liver functions tests and allergic reactions (Natural Medicines 2022).
Contraindications
There is a lack of reliable information on safety in pregnancy or breast-feeding (NMD 2022). Long-term use of Spirulina supplements by the mother was found to be related to hypercalcaemia in a newborn baby who developed generalised seizures (Moulis 2012).
Interactions
There is a theoretical interaction between blue-green algae and immunosuppressant drugs due to the possible immune-stimulating effects of the algae (NMD 2022). A theoretical risk also exists of an increased risk of bleeding with anticoagulants and anti-platelet agents and of hypoglycaemia in diabetes.
Warnings
Blue-green algae products have been found to be contaminated with potent toxins known as microcystins (NMD 2022; MSKCC 2020). Contamination may be more likely for algae grown in natural settings rather than under controlled conditions as is usually the case for commercially available spirulina products (NMD 2020). Microcystins can cause hepatotoxicity, nephrotoxicity and neurotoxicity (MSKCC 2020) which may be fatal, particularly in children who are more sensitive to the toxic effects (NMD 2022).
Symptoms of poisoning including abdominal pain and distention, nausea, vomiting, weakness, excessive thirst, rapid and weak pulse and shock, generally occur between 30 minutes and 24 hours after ingestion (NMD 2022). Toxicology studies in 2012 found some blue-algae products available in Germany and Italy to be contaminated but the affected products were those containing a species other than spirulina Heussner 2012; Vichi 2012). The WHO has set a tolerable daily intake of microcystins in adults of 0.04 microgram/kg (WHO 2020).
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