Spirulina: A Natural Nutritional Supplement

Spirulinais the commonname given to cyanobacteria of the genus Arthrospira (formerly Spirulina). It proliferates by forming blooms on the surface of water bodies through photo-autotrophy, utilizing sunlight withits pigments. It measures between 0.3 and 0.5 mm and owes its blue-green colour to the phycocyanine and chlorophyll it contains. It naturally thrives in warm (25 °C), alkaline (pH 8-11.5), freshwatere nvironment srich in carbonates, bicarbonates, nitrates, phosphates, and iron. This cyanobacterium organizesin to a succession of cells forming spiral filaments [1].  Since the 1980s, spirulina, like other microalgae, has been of major scientific interest [2-5]. Spirulina has been produced commercially for about 20 years. Global production of spirulina is estimated at 20,000 t/year by 2017 [6]. It was presented as the "best food for the future" at the 1974 United Nations Food Conference, and several bodies within the United Nations and the WHO are actively working on the use of spirulina to combat acute malnutrition. Spirulina is grown in glasshouses or bioreactors. It'scan be eaten in powder or flake form. 

The aim of this article is to present an analysis and examine the conditions for effective use of spirulina.

Nutritional value 

Spirulina is a natural food with a high protein and iron content (Table 1). But, a man weighing 75 kilos needs to consume 60g of protein a day. The daily iron requirement for men is 10 mg. In reality, humans consume no more than 10 grams of spirulina a day [7]. By consuming 10 grams of spiruina a day, a man will consume the equivalent of 10 g of protein and 10 mg of iron.

Table 1: Composition table for 100 grams of spirulina [7].

Therapeutic effect

Spirulina is interesting for its beta-carotene and Phycocyan in content (Table 1). Beta carotene is an antioxidant that inhibits the oxidation of other molecules, it protects the body from free radicals. Phycocyanin a good stimulant for the immune system. Also, spirulina could improve muscular fatigue and endurance in athletes [8].

Various studies tend to prove that spirulina increases HDL cholesterol levels (known as good cholesterol) while reducing LDL cholesterol (bad cholesterol). But these claims have been confirmed by animal studies. Studies in humans are insufficient to determine a precise effective dose [9]. There are no studies proving that spirulina can be used as part of a slimming programme.

Products containing spirulina maybe contaminated  

Spirulina contamination can occur during handling (harvesting, washing, drying, storage, packaging, etc.). 

Risk 1: Bacterial contamination 

The strongly alkaline conditions of spirulina production (pH around 10) limit the development of most pathogenic microorganisms (Listeria, Salmonella, coliforms, etc.). However, contamination canoccur during subsequent handling [10]. 

A study conducted on 31 commercial samples of spirulinasold in the Greek market revealed bacterial contaminations, 469 heterotrophic bacterial species were identified, some of whichmaybepathogenic, including genera such as Pseudomonas [11]. 

Risk 2: Contamination by cyanotoxins 

The cyanobacteria and Cyanotoxins have been identified in batches of spirulina.

Cyanotoxins are intracellular molecules with a variety of structures. They are synthesised by microalgae  (Microcystis, Planktothrix, Aphanizomenon, Anabaena, Gloetrichia ) during their growth phase and end up in the water when cells die or undergo lysis. These cyanotoxins can be toxic if ingested, which is why spirulina-based food supplements are checked for their presence [12]. 

Cyanotoxins have been detected in batches of spirulina, generally at levels of around 0.1 µg/g. Cyanotoxin biosynthesis genes have been identified in batches of spirulina, indicating contamination [13,14]. 

Risk 3 : Contamination by heavy metals 

Spirulina accumulates a large number of heavy metals if they are present in its environment. This property means that particular attention needs to be paid to the inputs used in spirulina cultivation, especially water (levels of heavy metals authorised in Europe : cadmium 3mg/Kg; mercury 0.5 mg/gk; lead 5 mg/kg; arsenic 3mg/kg). In 2012, the CFDA, the body responsible for protecting public health in China, found lead contamination in 6 of the 8 spirulina brands tested, with thresholds exceeded by up to 820% [15]. 

Indiscriminate consumption a can lead to undesirable effects. 

Clinical data: notifications of effects to French health services (ANSES, French National Agency for Food, Environmental and Occupational Health and Safety): between 2009 and 2017, Anses received 49 reports of adverse effects potentially linked to the consumption of dietary supplements containing spirulina. These effectsi ncluded allergic, gastroenteric, rheumatologic, and uro-nephrologicreactions. Other types of effects, such as dermatological, hepatic, endocrine, or metabolic, werealsoreported, but the established causal relationships for these cases are low [16]. 

Table 2: sufficiently documented cases received by Anses between 2009 and February 2017 [17].

In Europe, in France, Anses advises against consumption by people with a history of allergies or who are vulnerable to muscular or liver problems. Apart from the risk of contamination, spirulina does not appear to present any health risk at low doses (up to several grams per day). Opt for consumption of between 3 and 5 g per day for an adult [18-23].

We note that spirulina consumption does not meet human nutritional requirements in terms of protein and iron. Spirulina has important therapeutic properties (antioxidant and immune system stimulant), but many of the properties attributed to spirulina by manufacturers are not always proven by studies in the scientific literature.

Consumers are advised to give priority to supply chains with the highest level of control. Apart from the risk of contamination, spirulina does not appear to present a health risk in low doses. However, given the characteristics of spirulina and the adverse reactions reported, the consumption of these food supplements is not recommended for people predisposed to allergies or certain health problems.

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