Spirulina is a blue-green algae known as one of the richest foods on the planet. Its many abilities also seem to be linked to spirulina's unusual composition. But what is it really? What does spirulina contain? What are spirulina's nutritional values?

Protein

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

Each protein is made up of a sequence of 20 amino acids, just as a word is made up of 26 letters.

The amino acids present in the protein can be supplied by the diet or manufactured by the body. However, some cannot be produced by the body: these are known as essential amino acids, of which there are 8 in adults and 10 in children. In the normal diet, animal proteins provide all these essential amino acids, whereas plant proteins are individually incomplete.

The missing amino acid(s) is then referred to as a "limiting factor", as it limits the manufacture of proteins using that amino acid. In the long term, an essential amino acid deficiency has the same effects as a protein deficiency. That's why it's important to vary your plant protein sources, so as to benefit from all these amino acids.

Spirulina's composition 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. Spirulina's membrane dissolves easily under the effect of gastric acidity, guaranteeing good assimilation of these 20 amino acids.

Lipids

Spirulina also contains lipids. Lipids make up nearly 14% of our body weight: they are the architects of our cell membranes. Lipids are organized in double layers to isolate the interior of cells from the environment in which they are immersed. The nature of these lipids modifies membrane flexibility and influences the quality of message transmission between cells.

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

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

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

Carbohydrates

Carbohydrates provide the direct energy content of a food. They represent 1.5% of body weight. When glucose is consumed, part of it is immediately absorbed into the cells, thanks to the action of insulin, while the rest is stored in the liver and muscles in the form of glycogen, an energy reserve.

Dry spirulina contains around 20% carbohydrates, mainly in the form of glycogen and rhamnose. Glycogen is the body's storage form for carbohydrates, which can be rapidly mobilized. These two sugars have very little effect on blood sugar levels , mobilizing insulin and therefore the pancreas to a minimum.

Vitamins

A component of spirulina, vitamins are responsible for metabolism, development and cellular protection. With the exception of vitamin D, which is synthesized by the skin, all vitamins must be supplied by thediet. At present, 13 of them are known, but their roles are not yet fully identified. Some of them can be stored in the body's fatty tissues 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, vitamin A intake 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 plant source of vitamin D.

Minerals

Minerals account for 6% of body weight. They are present in very large quantities, mainly in the skeleton, and must be supplied through thediet. The most interesting minerals in 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 that found in 70% cocoa dark chocolate.

Pigments

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

• Phycocyanin :
  This is spirulina's noblest element.
• Carotenoids :
  β-carotene belongs to this family of pigments and is particularly well represented in Spirulina, which contains 20 to 25 times more than carrots.
• Chlorophyll :
  A photosynthesis pigment, chlorophyll is present in Spirulina to the tune of 1%.

So, given the quantity and quality of spirulina's components, it can be said that it boasts 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.