Definition, history and properties


What is spirulina?

A high-value nutritional and therapeutic dietary supplement

Spirulina (Arthrospira platensis) is a micro-organism, which grows rapidly in photosynthesis. It is referred to as a ‘cyanobacterium’, for which the approximate term ‘blue-green alga’ is often used as a synonym, though not entirely accurately. Whilst the latter term was applied in the past to spirulina, and is hard for some to shake off, the organism is not properly speaking an alga. It grows naturally in the alkaline water of certain lakes, in warm, brackish waters.

It is typically 0.1 millimetre in length, looking like a miniscule green filament rolled into a great many closely-bound spirals.

Spirulina has been eaten in some communities in Chad for centuries and to this day. Nowadays it is used principally as a dietary supplement of great nutritional and therapeutic value. It is very rich in micronutrients which are easily absorbed by the human body, including beta-carotene (the basis for vitamin A), iron, vitamin B12, gamma-linolenic acid (GLA) and essential fatty acids. These micronutrients enable the body to grow properly and to maintain its vital functions.

Antenna has sequenced the spirulina genome

The spirulina genome was sequenced entirely in July 2009, by Antenna Technologies and two private Swiss companies – Biorigin SA and Fasteris – as well as the Haute École Spécialisée Hepia in Geneva, represented by its research group for Plants and Pathogens.

These parties registered the spirulina genome in the GenBank, thus making it publicly and freely accessible to all potential users and preventing any attempt to patent it. Any interested party can thereby make faster and greater progress in the many potential uses of the organism. These can include nutritional applications, in industrial ecology through carbon sequestration and, indeed, in the production of molecules for therapeutic ends. The complete sequencing of the spirulina genome also enables our own researchers in Antenna to respond to a concern occasionally voiced by certain biologists, namely, given the ability of many cyanobacteria, under certain circumstances, to produce powerful toxins, on where things stand on this front with spirulina.

A cyanobacterial foodstuff

Cyanobacteria are the prime bacteria capable of photosynthesis to produce oxygen. They can be either unicellular or multicellular. In the latter case, the cells accumulate in colony-type piles, typically in threads of aligned cells. These filaments are called ‘trichomes’.

They are thus real prokaryotes, organisms with no nuclear membrane. This is despite their photosynthetic system being close to that of eukaryotes which contain chlorophyll-a and a II photosystem (PS-II).

This photosystem, together with photosynthetic pigments, accessory pigments and elements for transporting electrons, are all included in the thylacoidal membranes containing so-called phycobilisome granules. It is these granules which, in particular, hold phycocyanin, a pigment which is key to delivering energy to the PS-II. Phycocyanin is a protein comprising a polypyrrole-type prosthetic group; this gives it a blue-ish colour, as well as extremely efficient red fluorescence.

Cyanobacteria are able to absorb carbon through the Calvin cycle and they store energy and carbon in the form of glycogen. They have a considerable variety of metabolic structures, but they all share a lack of the full Krebs cycle.

A sizeable number of cyanobacteria, in particular many of the filamentous ones, are capable of nitrogen fixation, thanks to their specialised heterocyst structures.

Learn more (in French) Quelques bases scientifiques et analyse de l’ADN de la spiruline, Antenna Technologies, 2009

Rediscovered in Chad: from dihé to today

The first written records of spirulina date from the 16th century, the time when the Spanish set off on a conquest of South America, and Mexico in particular. It was eaten by the Aztecs who harvested it from lake, water, mixing it with maize to eat.

Spirulina resurfaced in the 1950s, when it was (re-)discovered by a mission of European scientists in Chad. Dried biscuits were found on sale in markets in the Kanem region, green with a blue hue and bearing the name of ‘dihé’. Further enquiries revealed that dihé was made of masses of a single micro-organism harvested from strongly alkaline local waters, and then dried just on the sands along the shoreline.

The micro-organism proved to be capable of photosynthesis and reproduced itself at a rapid pace. It was given the name ‘spirulina’ because of the filamentous spiral that was visible under a microscope. Its botanical name is ‘Arthrospira platensis’.

The Kanem region in Chad is a desert, scattered with small, temporary lagoons known as ‘wadis’. The subsoil is rich in a mixture of carbonates and salt (natron), which makes the waters of the wadi particularly alkaline – it is this medium which is very favourable for micro-algae to grow. Spirulina has been a very special and much sought-after foodstuff for centuries throughout Kanem; it is also heavily traded across the Sahel. At regular intervals, local communities harvest the spirulina from the wadis and filter it with water in tightly-woven wicker baskets. The resulting mass looks like a dark-green purée. To prepare it for conserving and sale, it is dried in the open sun, just lying on the sand. Once dry, it is broken into largish chunks which keep a long time in dry conditions.

Will the virtuous spiral reach tomorrow?

By the 1970s, the boundless doctor and spirulina devotee Ripley D Fox was criss-crossing the world to set up production sites in India, Africa, Vietnam, Peru and China, calling them ‘spirulina farms’. His mission: to deliver a practical response for Third World countries to defeat malnutrition and famine, especially amongst children.

In the West, large swathes of the general public have taken a liking to spirulina, in their endless quest for natural dietary supplements. It has been on the market for a long time in the USA, Europe, Japan and China. In the latter, it is mass produced by big laboratories, albeit with some production processes, especially the drying process, causing industrial spirulina to lose many of its nutritional qualities.

As a result of the surge in mass production in China, this one country alone represents 50% of the world market. It has even declared spirulina to be a ‘national food’.

All the while, more and more scientific studies on the nutritional and therapeutic benefits of spirulina are adding ever-growing weight to this surge of production in ponds and growth tanks across the world. Its recognition at the political level, unlike on the market, has been a long time in the making. This is, as it were, an unnatural brake on its adoption in developing countries, where small production units and farms are multiplying in numbers, to bring spirulina to malnourished children.

Nutritional aspects

Spirulina offers a truly appealing range of characteristics, which have long attracted researchers, private companies and organisations such as Antenna. It is impressively rich in proteins, rare essential lipids, and numerous minerals and vitamins. It has a phenomenal growth rate in totally mineral media. Not having any cellulose surfaces, it is perfectly digestible in both its raw and dried forms. Numerous nutritional tests have demonstrated the high bioavailability of its micronutrients.

Our field trials have shown that a child suffering from mild to moderate malnutrition can recover with a daily dose of 1 to 3 grams over a period of four to six weeks. We have supported the establishment of many spirulina cultivation units and can reassure anyone with an interest in the subject of the relative ease of growing crops that retain their nutritional benefits.

A packed table of contents

  • Exceptionally high protein content (between 50 and 70% of its dry weight, a level almost twice as high as for soya)
  • Exceptionally high provitamin A – beta-carotene content (one gram of spirulina covers the daily requirements of vitamin A for an adult)
  • Exceptionally high vitamin B12 content(four times higher than raw liver)
  • Exceptionally high iron content and a high content of minerals such as phosphorus, potassium, calcium, magnesium, selenium and iodine
  • Excellent source of zinc, when produced in growth tanks to which zinc has been added
  • Very high content gamma-linolenic acid (GLA content). GLA is the precursor to anti-inflammatory and immune mediators, and is the second richest source of this nutrient after breast milk.
  • Vitamins B1, B2, B3, B5, B6, B7, B8 and B9, vitamin D, vitamin E and vitamin K
  • The eight essential amino acids which the body cannot synthesise: isoleucine (required for optimal growth); leucine (stimulator of brain functions), lysine (necessary for producing antibodies, enzymes and hormones), methionine (rich in sulphur, has antioxidant properties), phenylalanine (required by the thyroid gland), threonine (improves intestinal and digestive functions), tryptophan (regulates serotonin) and valine (naturally stimulates mental and physical capacities).
  • Some 15 pigments, including chlorophyll and phycocyanin, which have anti-inflammatory, antioxidant and antitumour properties.

Learn more: Spirulina: Nutritional Aspects, J. Falquet and J.-P. Hurni, Antenna Technologies, 2006

In addition to its nutritional aspects, spirulina is also rich in therapeutic properties. Several of the molecules found in spirulina have been studied for their biological activities. Its immunostimulants and antivirals in particular are of great interest in the field of malnutrition, which weakens the immune defences of a malnourished child.

Significant potential for spirulina in malnourished patients infected with HIV in Africa.

A study conducted in Cameroon, published on 2 May 2011 in Nutrition and Metabolic Insights , is now showing its nutritional efficiency in terms of weight gain in malnourished people infected with HIV. This study also shows a revival of immunity-markers and a decrease in viral load, linked to the additional therapeutic properties of spirulina, which is a clinical observation of particular interest. The authors conclude that this new study “confirms the interest in considering this alga routinely for nutritional rehabilitation among this type of patients”.

Nutritional care of people living with HIV/AIDS remains a serious problem in Africa, partly due to the fact that malnutrition and HIV mutually reinforce each other. Spirulina, on the basis of its micronutrient composition, its health benefits and the fact that it is grown locally, demonstrates important advantages in the fight against malnutrition. In addition to its specific nutritional properties, spirulina also has therapeutic properties of particular interest in this type of patient, including antiviral and immunostimulatory properties.

Clinical studies have evaluated the effectiveness of an spirulina-based approach on the evolution of anthropometric, biological and nutritional parameters in malnourished patients infected with HIV in Africa. In Burkina Faso, a pioneering study of nutritional rehabilitation on 170 children showed a particularly favourable impact on the re-nutrition of HIV-infected children with locally produced spirulina.

This study was conducted with spirulina in 52 malnourished HIV-positive adults, naive to antiretroviral treatment. The randomised single-blind study compared a group of patients supplemented with spirulina with a group receiving soya beans, a standard nutritional rehabilitation supplement.

The biological parameters of patients were measured at baseline and after 12 weeks follow-up. At the endline of 12 weeks, weight and body mass index (BMI) were significantly increased in both groups (P = 0.01). In both groups, CD4 markers of immunological activity had also increased significantly (P <0.001). However, the increase was significantly larger in the group receiving spirulina (P = 0.02). Similarly, in both groups, the HIV viral load was significantly reduced. The decrease was significantly greater among patients receiving spirulina (P=0.02).

Article by M. Azabji-Kenfack and team: Potential of Spirulina Platensis as a Nutritional Supplement in Malnourished HIV-Infected Adults in Sub-Saharan Africa: A Randomised, Single-Blind Study. Nutrition and Metabolic Insights 2011:4 29–37.