Spirulina is a blue-green algae known as one of the richest foods on the planet. Its numerous capacities also seem to be linked to the composition of spirulina which is out of the ordinary. But what is it really? What does spirulina contain? What are the nutritional values of spirulina?

The proteins

Present in spirulina, proteins are the building blocks of muscle, it is the most represented element in the body after water (nearly 62% of body weight in water and 17% in protein). They are also the basis of many metabolic processes (immunity, cell repair ...) and constitute a large number of enzymes, hormones.

Each protein is made up of a sequence using 20 amino acids on the same principle that a word uses a sequence of 26 letters.

These amino acids present in the protein can be brought by the food or manufactured by the body. However, some cannot be produced by the body, these are called essential amino acids, 8 in adults and 10 in children. In the current diet, animal proteins provide all of these essential amino acids, whereas vegetable proteins are individually incomplete.

The missing amino acid(s) are then called "limiting factors" because they limit the manufacture of proteins using that amino acid. In the long term, a deficiency in essential amino acids has the same effects as a deficiency in protein. This is why it is important to vary the sources of vegetable proteins in order to benefit from all these amino acids.

The composition of spirulina is very rich in proteins(60-70% of its dry weight) [1] of high biological value. It contains all the essential amino acids for both adults and children. The membrane of spirulina dissolves easily under the effect of gastric acidity, which guarantees the good assimilation of these 20 amino acids.

Lipids

The composition of spirulina also contains lipids. Lipids constitute nearly 14% of our weight: they are the architects of our cell membranes. The lipids are organized in a double layer to isolate the interior of the cells from the environment in which they bathe. The nature of these lipids modifies the membrane flexibility and influences the quality of the transmission of messages between cells.

Lipids are also found in the nervous system (the brain contains 60%). They create a sheath around the nerves, which allows a much faster conduction of information.

Finally, the lipids contained in the adipose tissue play a role in energy storage and thermal regulation.

The lipids of spirulina represent 2 to 4% of its total weight. They present an optimal balance between omega-3 and 6, guaranteeing a good cardiovascular health. Spirulina is particularly rich in essential fatty acids with a high level of alpha-linolenic acid (ALA) and gamma-linolenic acid (GLA)[2], which are involved in hormone synthesis. GLA is only found in borage, evening primrose and blackcurrant oils as well as in breast milk and spirulina. The subclass of dihomo gamma-linolenic acid (DGLA) is, for its part, only present in spirulina and breast milk. These fatty acids are provided by the diet or transformed by the body from omega-6.

Carbohydrates

Carbohydrates provide the direct energy contribution of a food. They represent 1.5% of body weight. When glucose is consumed, part of it is immediately integrated into the cells thanks to the intervention of insulin, the other part is stored in the liver and muscles as glycogen, an energy reserve.

Present at about 20% in dry spirulina, its carbohydrates are mainly provided in the form of glycogen and rhamnose. Glycogen is the form of storage of carbohydrates in the body that can be quickly mobilized. These two sugars have very little effect on blood sugar levels and mobilize insulin and therefore the pancreas in a minimal way.

Vitamins

Vitamins are components of spirulina and are responsible for metabolism, development and cellular protection. Except for vitamin D which is synthesized by the skin, all vitamins must be provided by thediet. Currently 13 of them are known but their roles are not yet fully identified. Some of them can be stored in the fatty tissues of the body or in the liver and muscles (vitamins A, B9, B12, D and E).

The most interesting vitamins present in spirulina are :

• Vitamin A:
  In the form of β-carotene (precursor of vitamin A). With spirulina, the intake of vitamin A is adapted to needs; hypervitaminosis (pathological) is therefore impossible - unlike supplements containing vitamin A - and not its precursor. Vitamin A contributes to the normal functioning of the immune system
• Vitamin B1:
  Spirulina is the second richest source of vitamin B1; only brewer's yeast is richer.
• Vitamin B2:
  Spirulina is the fourth richest food in vitamin B2.
• Vitamin B12:
  Spirulina contains two forms of vitamin B12, cobalamin and pseudo-cobalamin, each with defined roles.
• Vitamin D:
  Spirulina is the most important vegetable source of vitamin D.

The minerals

Minerals represent 6% of the body weight. They are present in very large quantities mainly in the skeleton, and must be provided by thediet. The most interesting minerals of spirulina are :

• Calcium:
  Spirulina contains as much calcium as whole milk
• Iron:
  Spirulina contains highly assimilable iron.
• Magnesium:
  Spirulina contains a high level of magnesium, 10% higher than the content of dark chocolate 70% cocoa.

Pigments

Spirulina is a blue-green micro-algae containing a large number of pigments.

• The phycocyanine:
  It is the most noble element of spirulina.
• Carotenoids:
  β-carotene is part of this family of pigments and is particularly well represented in Spirulina which contains 20 to 25 times more than carrots.
• Chlorophyll:
  Pigment of photosynthesis, it is present up to 1% in spirulina.

Thus, in view of the quantity and quality of the components of spirulina, it is possible to say that it has a particularly interesting and complete nutritional composition.

Sources

[1] Teuling E. & al. (2017) Comparison of Protein Extracts from Various Unicellular Green Sources. J Agric Food Chem. 2017 Sep 13;65(36):7989-8002. doi: 10.1021/acs.jafc.7b01788.

[2] Otles S. & al: Fatty acid composition of Chlorella and Spirulina microalgae species. J AOAC Int. 2001 Nov-Dec;84(6):1708-14.