Spirulina (dietary supplement)
Spirulina is the dried biomass of cyanobacteria (blue-green algae) that can be consumed by humans and animals. The three species are Arthrospira platensis, A. fusiformis, and A. maxima.
Cultivated worldwide, "spirulina" is used as a dietary supplement or whole food.<ref name="medline-plus">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is also used as a feed supplement in the aquaculture, aquarium, and poultry industries.<ref name="vonshak">Vonshak, A. (ed.). Spirulina platensis (Arthrospira): Physiology, Cell-biology and Biotechnology. London: Taylor & Francis, 1997.Template:ISBN</ref>
Use of the term
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Arthospira species are free-floating, filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-handed helix. They occur naturally in tropical and subtropical lakes with high pH and high concentrations of carbonate and bicarbonate.<ref name="FAO Spirulina Review" /> A. platensis occurs in Africa, Asia, and South America, whereas A. maxima is confined to Central America.<ref name="vonshak"/> Most cultivated spirulina is produced in open-channel raceway ponds, with paddle wheels used to agitate the water.<ref name="FAO Spirulina Review" />
Spirulina thrives at a pH around 8.5 and above and a temperature around Template:Convert. They are autotrophic, and do not need a living energy or organic carbon source.
Potential species differences
The species A. maxima and A. platensis were once classified in the genus Spirulina. The common name, spirulina, refers to the dried biomass of A. platensis,<ref>Template:Cite book</ref> which belongs to photosynthetic bacteria that cover the groups Cyanobacteria and Prochlorophyta. Scientifically, a distinction exists between spirulina and the genus Arthrospira, for which the two species were originally proposed. Species of Arthrospira have been isolated from alkaline brackish and saline waters in tropical and subtropical regions. Among the various species included in the genus Arthrospira, A. platensis is the most widely distributed and is mainly found in Africa, but also in Asia. The term "spirulina" (without italicizing and usually without capitalization) remains in use for historical reasons.<ref name="vonshak"/>
Historical use
Spirulina was a food source for the Aztecs and other Mesoamericans until the 16th century; the harvest from Lake Texcoco in Mexico and subsequent sale as cakes were described by one of Cortés's soldiers.<ref>Diaz Del Castillo, B. The Discovery and Conquest of Mexico, 1517–1521. London: Routledge, 1928, p. 300.</ref><ref name="OsborneKahn2005">Template:Cite book</ref> The Aztecs called it tecuitlatl.<ref name="FAO Spirulina Review">Template:Cite FTP</ref>
Spirulina was found in abundance at Lake Texcoco by French researchers in the 1960s, but no reference to its use by the Aztecs as a daily food source was made after the 16th century, probably because of the draining of the surrounding lakes for agriculture and urban development.<ref name="FAO Spirulina Review" /> The topic of tecuitlatl, which was discovered in 1520, was not mentioned again until 1940, when the Belgian phycologist Pierre Dangeard mentioned a cake called dihe consumed by the Kanembu tribe, who harvest it from Lake Chad in the African nation of Chad. Dangeard studied the dihe samples and found it to be a dried puree of the spring form of the blue-green algae from the lake. The dihe is used to make broths for meals, and also sold in markets. The spirulina is harvested from small lakes and ponds around Lake Chad.<ref>Template:Cite journal</ref>
During 1964 and 1965, the botanist Jean Leonard confirmed that dihe is made up of spirulina, and later studied a bloom of algae in a sodium hydroxide production facility. As a result, the first systematic and detailed study of the growth requirements and physiology of spirulina was performed as a basis for establishing large-scale production in the 1970s.<ref name="vonshak" /><ref name=":0" /> Template:Nutritionalvalue
Nutrition
Dried spirulina is 5% water, 24% carbohydrates, 8% fat, and 57% (protein (table). In a reference amount of Template:Cvt, dried spirulina powder supplies Template:Convert and is a rich source (20% or more of the Daily Value, DV) of numerous essential nutrients, particularly B vitamins (thiamin, riboflavin, and niacin, and dietary minerals, such as iron and manganese (table).
The lipid content of spirulina is 8% by weight providing the fatty acids, gamma-linolenic acid,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> linoleic acid, stearidonic acid,<ref>Template:Cite journal</ref> eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid.<ref name="biomass">Template:Cite journal</ref> In contrast to those 2003 estimates (of DHA and EPA each at 2 to 3% of total fatty acids), 2015 research indicated that spirulina products "contained no detectable omega-3 fatty acids" (less than 0.1%, including DHA and EPA).<ref>Template:Cite journal</ref>
Vitamin B12
Spirulina contains no vitamin B12 naturally, and spirulina supplements are not considered a reliable source of vitamin B12, as they contain predominantly pseudovitamin B12 (Coα-[α-(7-adenyl)]-Coβ-cyanocobamide),<ref>Template:Cite journal</ref> which is biologically inactive in humans.<ref name="watanabe-review"/><ref name=ADA2009/> In a 2009 position paper on vegetarian diets, the American Dietetic Association stated that spirulina is not a reliable source of active vitamin B12.<ref name="ADA2009">Template:Cite journal</ref> The medical literature similarly advises that spirulina is unsuitable as a source of B12.<ref name="watanabe-review">Template:Cite journal</ref><ref>Template:Cite journal</ref>
Animals and aquaculture
Various studies on spirulina as an alternative feed for animal and aquaculture have been done.<ref name=":0" /> Spirulina can be fed up to 10% for poultry<ref>Template:Cite journal</ref> and less than 4% for quail.<ref>Template:Cite journal</ref> An increase in spirulina content up to Template:Cvt for 16 days in 21-day-old broiler male chicks resulted in yellow and red coloration of flesh, possibly due to the accumulation of the yellow pigment zeaxanthin.<ref>Template:Cite journal</ref> Pigs<ref>Template:Cite journal</ref> and rabbits<ref>Template:Cite journalTemplate:Dead link</ref> can receive up to 10% of the feed and increase in the spirulina content in cattle resulted in increase in milk yield and weight.<ref name=":1">Template:Cite journal</ref> Spirulina has been established<ref name=":0" /> as an alternative feedstock and immune booster for bigmouth buffalo,<ref name=":1" /> milk fish,<ref>Template:Cite journal</ref> cultured striped jack,<ref>Template:Cite journal</ref> carp,<ref>Template:Cite book</ref><ref>Template:Cite journal</ref> red sea bream,<ref>Template:Cite journal</ref> tilapia,<ref>Template:Cite journal</ref> catfish,<ref>Template:Cite thesis</ref> yellow tail,<ref>Template:Cite journal</ref> zebrafish,<ref>Template:Cite journal</ref> shrimp,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> and abalone,<ref>Template:Cite journal</ref> and up to 2% spirulina per day in aquaculture feed can be safely recommended.<ref name=":0" />
Research
According to the U.S. National Institutes of Health, scientific evidence is insufficient to recommend spirulina supplementation for any human condition, and more research is needed to clarify whether consumption yields any benefits.<ref name=medline-plus/> Administration of spirulina has been investigated as a way to control glucose in people with diabetes, but the European Food Safety Authority rejected those claims in 2013.<ref>Template:Cite journal</ref> Spirulina has been studied as a potential nutritional supplement for adults and children affected by HIV, but there was no conclusive effect on risk of death, body weight, or immune response.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Spirulina was investigated to address food security and malnutrition, and as dietary support in long-term space flight or Mars missions.<ref name="riley">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Risks
Spirulina may have adverse interactions when taken with prescription drugs, particularly those affecting the immune system and blood clotting.<ref name=medline-plus/>
Safety and toxicology
A number of cyanobacteria, of which spirulina is one, produce toxins such as microcystins.<ref name="lactmed">Template:Cite journal</ref> Some spirulina supplements have been found to be contaminated with microcystins, albeit at levels below the limit set by the Oregon Health Department.<ref name="gilroy" /> Microcystins can cause gastrointestinal upset, such as diarrhea, flatulence, headache, muscle pain, facial flushing, and sweating.<ref name=medline-plus/><ref name=lactmed/> Chronic exposure may lead to liver damage.<ref name="medline-plus" /> The effects of chronic exposure to even low levels of microcystins are a concern due to the risk of toxicity to several organ systems.<ref name="medline-plus" /><ref name="gilroy" />
These toxic compounds are not produced by spirulina itself,<ref name="belay">Template:Cite book</ref> but can occur if spirulina batches are contaminated with other, toxin-producing, blue-green algae. Because the U.S. considers spirulina a dietary supplement, its government does not regulate its production and enforces no safety standards for its production or purity.<ref name="gilroy">Template:Cite journal</ref> The U.S. National Institutes of Health describes spirulina supplements as "possibly safe", provided they are free of microcystin contamination, but "likely unsafe" (especially for children) if contaminated.<ref name=medline-plus/> Given the lack of regulatory standards in the U.S., some public-health researchers have raised the concern that consumers cannot be certain that spirulina and other blue-green algae supplements are free of contamination.<ref name="gilroy"/> In 2016, a review by Health Canada of available literature found that spirulina products contained varying levels of microcystins. Health Canada restricts microcystin-LR levels in products containing cyanobacteria to 0.02 μg per kilogram of body weight per day in finished products, or a maximum of 1 part per million in raw materials.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Heavy-metal contamination of spirulina supplements has also raised concern. The Chinese State Food and Drug Administration reported that lead, mercury, and arsenic contamination was widespread in spirulina supplements marketed in China.<ref name="wp-china">Template:Cite news</ref> One study reported the presence of lead up to 5.1 ppm in a sample from a commercial supplement.<ref name=":0">Template:Cite journal</ref> Spirulina doses of 10 to 19 grams per day over several months have been used safely.<ref name=medline-plus/>
Safety issues for certain target groups
Like all protein-rich foods, spirulina contains the essential amino acid phenylalanine (2.6–4.1 g/100 g),<ref name="FAO Spirulina Review" /> which should be avoided by people who have phenylketonuria, a rare genetic disorder that prevents the body from metabolizing phenylalanine, which then builds up in the brain, causing damage.<ref>Template:Cite journal</ref>
Microcystins have various potential toxicity, especially to children and pregnant women,<ref name="tap">Template:Cite journal</ref> including liver damage, shock, and death.<ref name=medline-plus/>
In 2024, a literature review on the allergic properties of spirulina was published. It was noted that to date (by July 2023), there have been 5 cases of allergy to spirulina, with 4 out of 5 cases resulting in anaphylaxis according to the classification from the World Allergy Organization's Anaphylaxis Guidance of 2020. Based on their research findings, instances of spirulina allergy are infrequently reported or identified.<ref>Template:Cite journal</ref>
See also
References
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