As a result of rising mortality rates due to cardiovascular diseases (CVDs), there has been a growing urgency to find alternative approaches to conventional pharmaceutical treatment to prevent the onset of chronic diseases. Arthrospira platensis, commonly known as Spirulina, is a blue-green cyanobacterium, classified as a “superfood”, used worldwide as a nutraceutical food supplement due to its remarkable nutritional value, lack of toxicity, and therapeutic effects. Many research studies have demonstrated that Spirulina has therapeutic functions such as antioxidant, anti-inflammatory, hypolipidemic, antidiabetic, and brain-protective properties.
1. Introduction
Arthrospira platensis is a photosynthetic, microscopic filamentous blue-green microalga classified as a cyanobacterium belonging to the Microcoleaceae family
[1].
A. maxima and
A. platensis, commonly known as “
Spirulina”, are the two most studied species for their considerable nutritional and therapeutic properties.
Spirulina inhabits tropical regions, particularly alkaline lakes with a pH 11 and a high concentration of carbonate and bicarbonate salts. Additionally, these algae can survive in extreme environments, such as the frozen lakes of Antarctica
[2][3]. These microorganisms were first discovered in Lake Texcoco in Mexico. The Aztecs were among the first to incorporate this microalga into their diet, particularly in the creation of a blue-green cake known as “tecuitlatl”, as unearthed by the Spanish army during their conquest of Mexico
[4]. Since ancient times,
Spirulina has been utilized for its beneficial characteristics. Today,
Spirulina is still used in a wide range of applications. In recent decades, it has garnered the classification of a “superfood” because of its copious protein content (60–70% by dry weight) as well as its abundance of carbohydrates, essential fatty acids, vitamins, minerals, and pigments like carotenes, chlorophyll a, and phycocyanin
[5]. Because of its impressive nutritional value, is widely utilized in both the food and pharmaceutical fields. In the food industry,
Spirulina is used as a nutraceutical food supplement, added to foods such as baked goods, beverages, dairy products, sports supplements, and baby food
[6]. On the other hand, the pharmaceutical sector has produced tablets, dehydrated powders or encapsulated forms, which are marketed as “nutraceuticals”
[7].
As a consequence of the considerable market demand for
Spirulina products,
S. platensis has been classified as generally recognized as safe (GRAS) by the Food and Drug Administration (FDA)
[8]. Many research studies have demonstrated that
Spirulina has therapeutic functions such as antioxidant, anti-inflammatory, hypolipidemic, antidiabetic, and brain-protective properties
[9][10][11]. Remarkably, the abundant presence of natural pigments endows
Spirulina with antioxidant potential, notably carotenoids and C-phycocyanin
[12][13]. Several research investigations indicated that β-carotene, diadinoxanthin, diatoxanthin, and C-phycocyanin exhibited very high scavenging activity
[14][15]. Thanks to its antioxidant properties, this microalga is considered beneficial in preventing cardiovascular diseases
[11]. Today, CVDs are the main cause of death globally
[16]. Therefore, drug therapies used today to prevent certain predisposing disorders such as diabetes, hypertension, and dyslipidemia display many benefits and, at the same time, some adverse effects. For this reason, the use of nutraceuticals, such as
Spirulina, has been shown promising results as a support therapy for the maintenance of cardiovascular health and the reduction in cardiovascular risk
[17][18]. This renewed focus on functional-food-based therapy is now seen as a new strategy to achieve a healthy generation. In the 21st century, it is essential to follow the ideologies established by Hippocrates (460–377 B.C.), who claimed “Let food be your medicine”
[19].
In the last decade, there has been a gradual increase in individuals afflicted with type 2 diabetes
[20]. Diabetes mellitus (DM) represents a complex disease marked by elevated glucose levels and an increased basal metabolic rate because of a defect in insulin signaling.
In these conditions, hyperglycemia adversely affects the integrity of cellular membranes, leading to insulin resistance in both the liver and peripheral tissues and producing reactive oxygen species (ROS)
[21].
Moreover, type 2 diabetes accounts for approximately 90% of all diagnosed cases of diabetes and is considered a risk factor for the development of CVDs, including myocardial infarction, peripheral vascular disease (PVD), heart failure, stroke, retinopathy, and neuropathy, as a result of microvascular and macrovascular complications due to hyperglycemia
[22].
One of the proposed pharmacological approaches to treat hyperglycemia in diabetes is the utilization of metformin
[23]. Generally, metformin has no impact on lipid profiles in subjects diagnosed with type 2 diabetes
[24].
However, it is important to note that before considering the use of metformin, which can induce side effects of similar to those of digestive disorders, such as diarrhea and nausea
[25], there are preventive measures that can be taken to avoid the development of diabetes. Pre-diabetes is a condition that occurs before the onset of diabetes, where blood sugar levels are higher than the normal range but not high enough to be considered type 2 diabetes.
Although it is often not possible to avoid the onset of the disease, exercise and food supplements can delay or improve the management of the disease because of improvements insulin sensitivity
[26]. Furthermore, the bioactive ingredients contained in some food supplements, such as polyphenols, polysaccharides, and others, can affect the modulation of glucose metabolism
[27].
Considerable research has focused on studying natural compounds with antihyperglycemic properties, such as
Spirulina. Furthermore, unlike metformin,
S. platensis not only reduces circulating glucose levels but can also influence lipoprotein metabolism, high levels of which are associated with diabetes. This would represent a possible cardiovascular benefit in diabetic patients
[28].
Spirulina has gained attention as a functional food due to its potential to lower blood glucose levels, control cholesterol, and provide antioxidant benefits.
2. Clinical Studies
A recent randomized, double-blind, placebo-controlled study included 60 patients under usual treatment with metformin for type 2 diabetes
[29]. The results suggest that 2 g of
Spirulina platensis given as four capsules before meals, in addition to metformin therapy, markedly improved glycemic parameters, including glycosylated hemoglobin (HbA1c) (
p < 0.001) and fasting blood glucose levels (FBS) (
p < 0.001), compared to the placebo group under metformin treatment only. Hence, the supplementation of 2 g/day of
S. platensis for 3 months is considered safe and free of side effects, making it an effective treatment option for the management of type 2 diabetes and its associated complications
[29]. In line with this evidence, Alam et al.
[30] evaluated that the administration of 7 g twice daily of
Spirulina powder in patients with no pharmacological treatment can reduce FBS (
p < 0.01) and postprandial glycemia (PPBS) similarly to the control group who received two capsules of 500 mg metformin before meals for 45 days. The authors observed no statistically significant differences in HbA1C levels induced by
Spirulina treatment. As stated by the authors, this scenario could probably be due to the short duration of treatment and the small sample size. Further studies are needed to evaluate its pharmacological effect and its usefulness as a reliable alternative to classic antidiabetic agents
[30]. Sowjanya and colleagues
[31] divided diabetic patients into two groups. The first group (EG-1) was given 2 g of
Spirulina contained in two snack bars (25 g each) in the mid-morning and evening. The second group (EG-2) was given two
Spirulina capsules in the morning and evening, while the control group was given no supplementation. In both the EG-1 and EG-2 groups, their FBS, PPBS and HbA1c levels were significantly more reduced from the baseline to the endpoint both in males (
p < 0.01) than in females (
p < 0.05). In the EG-1 group, the reduction in FBS and PPBS levels was greater than in the EG-2 group, possibly due to the synergistic effects of other nutritional ingredients. In addition, the reduction in FBS and PPBS in females is lower than that in males
[31]. Another clinical study showed that 2 g/day of
Spirulina capsules, taken during lunch and dinner for 2 months, led to a reduction in FBS, PPBS, and HbA1c (
p < 0.05) from the baseline to the endpoint
[32]. A similar effect was induced by a dosage of 8 g of
Spirulina administered daily for 3 months in tablet form to 50 patients with type 2 diabetes treated with their usual antidiabetic therapy, but the reduction in HbA1c levels was not significant. It is possible that
Spirulina can lower serum glucose levels in the short term, but it may require a longer treatment period to affect hemoglobin A1C levels
[33]. The reduction in the HbA1c level highlighted suggests an improvement in the regulation of long-term glucose management.
Moreover, in Cretan patients with non-alcoholic fatty liver disease (NAFLD), 6 g/day
Spirulina (Greek production) supplementation for six months led to a significant reduction in the HOMA-IR index, a measure representing an enhancement in insulin sensitivity
[34]. The main characteristics at the baseline and after
Spirulina supplementation of the included studies are shown in
Table 1.
Table 1. Detailed characteristics of the included studies on diabetic patients.
References |
Patients’ Cohort |
Dose of Spirulina |
Duration Treatment (Weeks/Months) |
Outcomes in Spirulina Group; (p-Value) |
Outcomes in Control Group; (p-Value) |
p-Value |
|
|
|
|
HbA1c (mg/dL) |
HbA1c (mg/dL) |
|
|
|
|
|
Baseline 8.87 ± 0.29 |
Baseline 8.47 ± 0.21 |
0.65 |
|
|
|
|
End 7.44 ± 0.20 |
End 8.15 ± 0.17 |
NA |
Karizi et al., 2022 [29] |
Spirulina + Metformin group; |
2 g/day |
3 months |
p = 0.001 |
p = 0.016 |
|
|
Placebo + Metformin group |
|
|
FBS (mg/dL) |
FBS (mg/dL) |
|
|
|
|
|
Baseline 167.30 ± 4.34 |
Baseline 227.60 ± 67.85 |
0.47 |
|
|
|
|
End 136.33 ± 4.42 |
End 165.47 ± 3.37 |
NA |
|
|
|
|
p = 0.001 |
p = 0.99 |
|
|
|
|
|
HbA1c (mg/dL) |
HbA1c (mg/dL) |
|
|
|
|
|
Baseline 9.73 ± 1.92 |
Baseline 9.61 ± 1.49 |
0.862 |
|
|
|
|
End 9.95 ± 2.11 |
End 9.15 ± 2.03 |
0.303 |
|
|
|
|
p = 0.525 |
p = 0.459 |
|
|
|
|
|
FBS (mg/dL) |
FBS (mg/dL) |
|
Alam et al., 2016 [30] |
Spirulina group; |
7 g/day |
45 days |
Baseline 245.53 ± 78.95 |
Baseline 227.60 ± 67.85 |
0.525 |
|
Placebo + Metformin group |
|
|
End 204.87 ± 78.15 |
End 191.80 ± 78.91 |
0.65 |
|
|
|
|
p = 0.003 |
p = 0.212 |
|
|
|
|
|
PPBS (mg/dL) |
PPBS (mg/dL) |
|
|
|
|
|
Baseline 345.73 ± 98.33 |
Baseline 329.60 ± 72.92 |
NA |
|
|
|
|
End 303.67 ± 96.16 |
End 282.80 ± 99.90 |
NA |
|
|
|
|
NA |
NA |
|
|
|
|
|
HbA1c (mg/dL) |
HbA1c (mg/dL) |
|
|
|
|
|
Baseline EG-I M 9.19 ± 0.88; W 8.88 ± 0.70 EG-II M 7.33 ± 0.54; W 7.20 ± 0.33 |
Baseline M 8.00 ± 1.05; W 8.64 ± 0.79 |
NA |
|
|
|
|
End EG-I M 7.11 ± 0.64; W 7.64 ± 0.48 EG-II M 6.48 ± 0.36; W 6.58 ± 0.35 |
End M 7.98 ± 1.03; W 8.62 ± 0.74 |
NA |
|
|
|
|
EG-I M p < 0.01; W p < 0.01 EG-II M p < 0.01 W p < 0.01 |
M n.s; W n.s |
|
|
EG1 group; |
|
|
FBS (mg/dL) |
FBS (mg/dL) |
|
Sowjanya et al., 2022 [31] |
EG2 group |
2 g/day |
3 months |
Baseline EG-I M 138.00 ± 18.39; W 128.08 ± 11.76 EG-II M 135.02 ± 18.22; W 132.33 ± 10.89 |
Baseline M 146.10 ± 25.29; W 135.12 ± 10.27 |
NA |
|
Control group |
|
|
End EG-I M 122.21 ± 14.48; W 111.00 ± 14.48 EG-II M 119.31 ± 14.33; W 123.12 ± 9.81 |
End M 141.43 ± 20.84; W 130.12 ± 9.76 |
|
|
|
|
|
EG-I M p < 0.01; W p < 0.01 EG-II M p < 0.01; W p < 0.05 |
M n.s; W n.s |
NA |
|
|
|
|
PPBS (mg/dL) |
PPBS (mg/dL) |
|
|
|
|
|
Baseline EG-I M 210.33 ± 28.99; W 212.12 ± 39.45 EG-II M 197.45 ± 23.31 W 190.03 ± 14.86 |
Baseline M 206.17 ± 22.83; W 179.24 ± 17.82 |
NA |
|
|
|
|
End EG-I M 165.56 ± 25.35; W 175.58 ± 32.11 EG-II M 171.28 ± 24.77 W 175.50 ± 18.38 |
End M 202.37 ± 22.76; W 172.09 ± 15.49 |
NA |
|
|
|
|
EG-I M p < 0.01; W p < 0.01 EG-II M p < 0.01; W p < 0.05 |
M n.s; W n.s |
|
|
|
|
|
HbA1c (mg/dL) |
HbA1c (mg/dL) |
|
|
|
|
|
Baseline 9.0 ± 2.3 |
Baseline 8.7 ± 1.5 |
NA |
|
|
|
|
End 8.0 ± 1.3 |
End 8.7 ± 1.3 |
NA |
|
|
|
|
p < 0.05 |
n.s |
|
|
|
|
|
FBS (mg/dL) |
FBS (mg/dL) |
|
|
|
|
|
Baseline 161.7 ± 48.6 |
Baseline 164.3 ± 59.4 |
NA |
Parikh et al., 2001 [32] |
Spirulina group; |
2 g/day |
2 months |
End 142.4 ± 27.4 |
End 165.1 ± 44.3 |
NA |
|
Control group |
|
|
NA |
NA |
|
|
|
|
|
PPBS (mg/dL) |
PPBS (mg/dL) |
|
|
|
|
|
Baseline 264.9 6 65.2 |
Baseline 215.2 6 67.3 |
NA |
|
|
|
|
End 248.8 6 68.9 |
End 212.3 6 57.6 |
NA |
|
|
|
|
NA |
NA |
|
|
|
|
|
FBS (mg/dL) |
|
|
Beihaghi et al., 2017 [33] |
Spirulina group; |
8 g/day |
3 months |
Baseline 158.1 ± 44.2 |
NA |
|
|
Control group |
|
|
End 127.8 ± 36.7 |
|
|
|
|
|
|
NA |
|
|
This entry is adapted from the peer-reviewed paper 10.3390/nu16050642