INTRODUCTION:

A tiny blue-green algae belonging to the Oscillateriaceae family, cyanobacteria are known as Spirulina (Arthrospira). It grows naturally in freshwater and marine environments in Asia, Africa, Europe, South America, and North America. It also thrives in alkaline and warm media. The Texcoco Lake in Mexico was formerly home to a large population of S. maxima subtype. There is evidence that the lake's products, known as tecuitlatl, were utilized as food during prehispanic times and that they were later collected, dried, and sold for human consumption during the conquest. Regretfully, over time, this practice was abandoned¹.

Spirulina is an extremely nutritious food that contains a wide range of macro- and micronutrients, such as iron, gamma-linolenic acid, sulfated polysaccharides, phycocanin, vitamins, and minerals²⁴ (ElBaky, 2008; Chu, 2010). Because of this, spirulina is of great interest because it may be used as a functional food¹⁹. Due to its organoleptic qualities, which might make it a viable food or nutritional supplement, and the fact that it has neither shown acute nor chronic toxicity, spirulina has also demonstrated good acceptability, indicating that it is safe for ingestion by humans¹.

Nutritional composition:

The circumstances used for cultivation and the analytical techniques might affect the content of the spirulina.

Protein and Amino Acids:

Protein makes up between 60 and 70 percent of the dry weight of spirulina. This is an extraordinary amount given that the bulk of plant-based foods—even those regarded as "good protein sources"—only comprise only 35%18. Actually, one of the main proteins found in Spirulina is C-phycocyanin, a molecule that contains phycocyanobilin, a homolog of biliverdin. It makes up over 20% of the dry weightof algae¹⁵.

The quality of the protein should be evaluated in addition to its amount, since this is dictated by the amino acid composition, availability, and ratio of the protein. Since spirulina includes all of the necessary amino acids, which make up over half of the protein, it offers a complete protein.

There are other features of spirulina protein that raise its nutritious content. For instance, its net protein utilization (NPU), which shows the proportion of ingested nitrogen that stays inside the organism, and its biologic value (BV), which quantifies the amount of nitrogen retained in the body relative to the amount of nitrogen absorbed¹⁹. Furthermore, the digestibility coefficient (DC), which measures how much of a food's nitrogen is really absorbed, is comparatively high for spirulina.

Additionally, the algae show a high protein efficiency ratio (PER), which is the most straightforward and widely used metric for assessing proteins in animal feeding experiments²⁰. The PER of the blue-green algae is significantly greater than that of other vegetable proteins, but being less than that of animal protein².

Table1: Protein Values of Spirulina as Compared to The Gold Standard

Characteristics	Spirulina	Reference protein (casein)	% Age of reference
Biological value	75	87	86.20
Net protein utilization	62	83	74.69
Digestibility	85	95	89.47
Protein efficiency	1.9	2.5	76.00

Lipids:

The lipid portion of spirulina is around 5–10% of its dry weight. The fact that the fats comprising this percentage are primarily lipids that humans require is significant in this regard. Therefore, it is thought that spirulina is an excellent source of oleic, linoleic, and gamma-linolenic acids¹⁶. The first has drawn a lot of interest since few food sources include a noticeable amount; in fact, spirulina is thought to be the vegetable source with the largest quantity (making up around 20% of its total fatty acid content). Since prostaglandins, leukotrienes, and thromboxanes are mediators of inflammation and immunological processes, they have a role in the development of disorders like arthritis. This highlights the significance of gamma-linolenic acid³.

Nucleic acids:

The DNA and RNA content in this fraction isSpirulina. Uric acid is produced during the catabolism of nucleic acids because purines, adenine and guanine, are broken down²¹. High uric acid levels have been linked to the onset of kidney stones, gout, and, more recently, heart conditions¹⁷.

Nucleic acids make about 4-6% of the dry weight of spirulina; this is significantly less than other single-cell protein sources (yeast, for example, comprises roughly 20% of its dry matter) and other microalgae, such as chlorella. The World Health Organization advises consuming no more than 4 g of nucleic acid per day; consuming up to 80 g of blue-green algae would provide the recommended amount².

Vitamins

Of all the vitamins, vitamin B12 is the largest and most complex; it represents all of the biologically active cobalamins. As with other seaweed, spirulina contains an extraordinarily high amount of vitamin B12. This is significant since such vitamin is often limited to meals with animal origins. Since vegans don't eat anything that comes from animals, this algae may be seen as a beneficial source for them³.

Another excellent source of beta-carotene is spirulina, which has a 700–1700 mg/kg concentration. Once absorbed, beta-carotene is biotransformed into vitamin A. Since humans only need around 1mg of vitamin A each day, 1-2 grams of algae will suffice to meet this need. Furthermore, in contrast to the use of commercial supplements, an overdose would be unlikely because preclinical and clinical investigations have confirmed the bioavailability of beta-carotene, which is more bioavailable than retinol and is not cumulatively toxic²².
The second most significant class of pigments present in algae are called carotenoids. Their function is to act as lipophylic antioxidants, and it is believed that they are the cause of carotene's anticancer properties⁴.

Mineral:

Iron, calcium, and phosphorus are the three inorganic nutrients that are most important to spirulina. Due to inadequate hemoglobin levels in erythrocytes, populations with low animal food consumption—due to personal beliefs, dietary choices, or accessibility—are more likely to experience iron deficiency¹⁸. This condition presents clinically as hypochromic and microcytic anemia²³. Furthermore, the same individuals frequently eat large amounts of fiber, which includes phytates and oxalates and reduces the bioavailability of iron from vegetable sources. Lastly, the only iron found in plant meals is non-heme iron, which is more vulnerable to absorption inhibitors (phytates, for example)⁵.

Human Studies on the Nutritional Potential of Spirulina:

Studies on people are much more rare than those on preclinical models. Spirulina has, however, been used as a reversal agent for protein undernutrition, with encouraging outcomes for weight growth and an improvement in overall nutritional status⁶.

In reference to protein, studies indicating positive outcomes for Mexican children or newborns experiencing acute malnourishment have been referenced. In a more thorough investigation, five malnourished people were given foods containing up to 50% protein from spirulina via a plastic tube for durations ranging from four to five days. There was a noticeable increase in weight and a favorable nitrogen balance, and no adverse effects were noted. Another African research used spirulina as a supplement for eight weeks to treat youngsters who were undernourished in protein or energy⁷. The number of children diagnosed with undernutrition decreased as a consequence, and nutritional status significantly improved. On average, the group supplemented with spirulina gained 25 g of weight each day, compared to the control group⁸.

Toxicological Studies:

Given that organisms may include poisons, antinutrients, or other potentially hazardous substances, the safety evaluation must take this matter into consideration (Howlett, 2003). Here, we provide a summary table III that displays the results of several toxicological experiments carried out on lab animals about the
human health assurance (adapted from Chamorro-Cevallos)⁹. It is noteworthy that when phycocyanin, the blue colorant found in spirulina, was given to rats of both sexes for 14 weeks at a dietary content of up to 5%, there were no signs of toxicity¹⁰.

Perspectives:

Nutritional supplements can be used for a variety of purposes, such as making up for a deficiency in calories, macronutrients (proteins, fats, carbs), or micronutrients (vitamins and minerals) in order to prevent or treat disease¹¹. The potential application of microalgae ingestion as a protein deficiency cure is the primary driver of interest in this practice. With an estimated incidence of over 300 million individuals worldwide, the latter impacts is a major issue. Due to its high concentration and exceptional quality—bioavailable iron and complete protein, as mentioned previously—spirulina may serve as a potential protein source¹².

Moreover, spirulina has not demonstrated any acute or chronic toxicity, therefore it may be used by humans without risk. The toxicological investigation revealed that the amounts of this algae were more than what would be expected from human intake¹³. Thus, it would seem that using this cyanobacterium as a source of single cell protein at this time has no toxicological risks²⁵.

Based on everything mentioned above, we can say that spirulina has many benefits, including a high nutritional value, easy nutrient availability, a straightforward production process because of its modest growth requirements, excellent preservation after recollection, and safety when it comes to consumption (no toxicities), to mention a few¹⁴.

In an effort to combat nutritional inadequacies using non-traditional means, spirulina appears to be the most promising strain, even though other microalgae, such as Chlorella, Dunaliella, and Scenedesmus, have also been utilized as food supplements²⁴.

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Received on 21.03.2024 Modified on 11.06.2024

Asian J. Pharm. Res. 2024; 14(3):315-318.

DOI: 10.52711/2231-5691.2024.00049