Spirulina represents a biomass of cyanobacteria (blue-green algae) that can be consumed by humans and other animals. There are two species, Arthrospira platensis and Arthrospira maxima.
Cultivated worldwide, Arthrospira is used as a dietary supplement or whole food. It is also used as a feed supplement in the aquaculture, aquarium and poultry industries.
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Etymology and ecology
The maxima and plaetensis species were once classified in the genus Spirulina. The common name, Spirulina, refers to the dried biomass of Arthrospira platensis, which belongs to photosynthetic bacteria that cover the groups Cyanobacteria and Prochlorophyta. Scientifically, there is distinction between Spirulina and Arthrospira genus. Species of the genus 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. Arthrospira maxima is believed to be found in California and Mexico. The term Spirulina remains in use for historical reasons.
Arthrospira species are free-floating filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-hand helix. They occur naturally in tropical and subtropical lakes with high pH and high concentrations of carbonate and bicarbonate. A. platensis occurs in Africa, Asia, and South America, whereas A. maxima is confined to Central America. Most cultivated spirulina is produced in open channel raceway ponds, with paddle-wheels used to agitate the water.
Spirulina thrives at a pH around 8.5 and above, which will get more alkaline, and a temperature around 30 °C (86 °F). They are able to make their own food, and do not need a living energy or organic carbon source. In addition, a nutrient feed for growing it is:
- Baking soda- 16 g/L (61 g/US gal)
- Potassium nitrate- 2 g/L (7.6 g/US gal)
- Sea salt- 1 g/L (3.8 g/US gal)
- Potassium phosphate- 0.1 g/L (0.38 g/US gal)
- Iron sulphate- 0.0378 g/L (0.143 g/US gal)
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' soldiers. The Aztecs called it "tecuitlatl".
Spirulina was found in abundance at Lake Texcoco by French researchers in the 1960s, but no reference to its use was made by the Aztecs as a daily food source after the 16th century, probably due to the draining of the surrounding lakes for agriculture and urban development. The topic of the Tecuitlalt, which was earlier discovered in 1520, was not mentioned again until 1940, the French phycologist Pierre Dangeard mentioned about a cake called "dihe", consumed by Kanembu tribe, African Lake Chad, Kanem (Chad, Africa). Dangeard studied the "dihe" samples and found that it is like a puree of spring form blue algae. Spirulina has also been traditionally harvested in Chad. It is dried into dihé, which are used to make broths for meals, and also sold in markets. The spirulina is harvested from small lakes and ponds around Lake Chad.
During 1964 and 1965, the botanist Jean Leonard, during his Belgian Trans-Saharan Expedition, confirmed that dihe is made up of Spirulina and thus chemical analysis was started on Spirulina. During that time, Léonard received a request from Sosa-Texcoco Ltd, Mexico, to study a bloom of algae in their sodium hydroxide production facility. As a result, the first systematic and detailed study of the growth requirements and physiology of Spirulina was performed. This study, which was a part of Ph.D. thesis by Zarrouk (1966) was the basis for establishing the first large-scale production plant of Spirulina. Spirulina, in 1967 was established as a "wonderful food source" by the International Association of Applied Microbiology.
The first large-scale spirulina production plant, run by Sosa Texcoco, was established there in the early 1970s.
Food and nutrition
As an ecologically-sound, nutrient-rich, dietary supplement, spirulina is being investigated to address food security, malnutrition, and as dietary support in long-term space flight or Mars missions. Its interest for food security is for lower land and water needs to produce protein and energy than required for livestock as meat sources.
Dried spirulina contains 5% water, 24% carbohydrates, 8% fat, and about 60% (51-71%) protein (table). It is a complete protein source, containing all essential amino acids.
Provided in its typical supplement form as a dried powder, a 100 gram amount of spirulina supplies 290 Calories and is a rich source (20% or more of the Daily Value, DV) of numerous essential nutrients, particularly B vitamins (thiamin and riboflavin, 207% and 306% DV, respectively) and dietary minerals, such as iron (219% DV) and manganese (90% DV) (table).
The lipid content of spirulina is 8% by weight (table) providing the fatty acids, gamma-linolenic acid, alpha-linolenic acid, linoleic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid.
Spirulina may have adverse interactions when taken with prescription drugs, particularly those affecting the immune system and blood clotting.
Vitamin B12
Spirulina does not contain vitamin B12 naturally (see table), and spirulina supplements are not considered to be a reliable source of vitamin B12, as they contain predominantly pseudovitamin B12, which is biologically inactive in humans. In a 2009 position paper on vegetarian diets, the American Dietetic Association stated that spirulina is not a reliable source of active vitamin B12. The medical literature similarly advises that spirulina is unsuitable as a source of B12.
Risks
Spirulina is a form of cyanobacterium, some of which are known to produce toxins such as microcystins, BMAA, and others. Some spirulina supplements have been found to be contaminated with microcystins, albeit at levels below the limit set by the Oregon Health Department. Microcystins can cause gastrointestinal disturbances and, in the long term, liver damage. The effects of chronic exposure to even very low levels of microcystins are of concern, because of the potential risk of toxicity to several organ systems and possibly cancer.
These toxic compounds are not produced by spirulina itself, but may occur as a result of contamination of spirulina batches with other toxin-producing blue-green algae. Because spirulina is considered a dietary supplement in the U.S., no active, industry-wide regulation of its production occurs and no enforced safety standards exist for its production or purity. 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. 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.
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. One study reported the presence of lead up to 5.1 ppm in a sample from a commercial supplement.
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), 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.
Spirulina contaminated with microcystins has various potential toxicity, especially to children, including liver damage, shock and death.
Animals and aquaculture
Various studies on spirulina as an alternative feed for animal and aquaculture were done. Spirulina can be fed up to 10% for poultry and less than 4% for Quail. Increase in the Spirulina content up to 40g/kg for 16 days in 21-day-old broiler male chicks, resulted in yellow and red coloration of flesh and this may be due to the accumulation of the yellow pigment, zeaxanthin. Pigs, and rabbits can receive up to 10% of the feed and increase in the Spirulina content in cattle resulted in increase in milk yield and weight. Spirulina as an alternative feedstock and immune booster for big mouth buffalo, milk fish, cultured striped jack, carp, red sea bream, tilapia, catfish, yellow tail, zebrafish, shrimps and abalone was established and up to 2% Spirulina per day in aquaculture feed can be safely recommended.
Toxicological studies of the effects of spirulina consumption on humans and animals, including feeding as much as 800 mg/kg, and replacing up to 60% of protein intake with Spirulina, have shown no toxic effects. Fertility, teratogenicity, peri- and postnatal, and multigenerational studies on animals also have found no adverse effects from Spirulina consumption.
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.
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. Spirulina is under research as a potential nutritional supplement for children affected by HIV.
Advocates
In 1974, the World Health Organization described spirulina as "an interesting food for multiple reasons, rich in iron and protein, and is able to be administered to children without any risk," considering it "a very suitable food." The United Nations established the Intergovernmental Institution for the use of Micro-algae Spirulina Against Malnutrition in 2003.
In the late 1980s and early 90s, both NASA (CELSS) and the European Space Agency (MELiSSA) proposed spirulina as one of the primary foods to be cultivated during long-term space missions.
Source of the article : Wikipedia
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