Once declared the “best food for the future” by the World Health Organization, this blue-green algae is a protein-rich antioxidant that can support and maintain your immune system. Read on to learn more about spirulina.

What is Spirulina?

Spirulina is a dried supplement made from two species of blue-green algae, Arthrospira platensis and Arthrospira maxima. The Kanembu tribe in Chad call it dihé; the Aztecs who lived in the valley of Mexico called it tecuitlatl [1, 2, 3, 4]. 

The algae naturally grows in warm freshwater lakes like Lake Texcoco in Mexico and Lake Chad, which sits on the border of Chad, Niger, Nigeria, and Cameroon. Locals traditionally harvest the algae and dry it in “cakes” [4].

Once it’s been dried, spirulina contains up to 70% protein, is a nutrient-rich antioxidant, and takes less land, water, and energy to produce than staple crops like corn and soy. Farmers use it to enrich their animal feeds and improve the quality of meat they produce. It pulls huge quantities of carbon dioxide out of the atmosphere, and it may even be used to convert city sewage back to clean water [1, 5].

Spirulina gathered attention as a possible pharmaceutical in the 1940s and 50s. In 1974, the World Health Organization declared it the “best food for the future” to combat malnutrition, especially in children [4].

Snapshot of Spirulina


  • A powerful antioxidant
  • High in protein and full of nutrients
  • Lowers blood sugar
  • Reduces inflammation, especially in allergies
  • May suppress cancer growth
  • Prevents fatigue
  • Protects the brain, heart, kidneys, and liver


  • May cause rare allergic reactions
  • Occasional contamination with other cyanobacteria
  • May interact with some medication



The most significant bioactive compounds in spirulina are the phycocyanins, including C-phycocyanin. This is a powerful antioxidant and anti-inflammatory molecule with a surprising cascade of effects: it has been found to protect brain and liver cells [1, 6].

C-phycocyanin has a very similar structure to the human blood protein bilirubin, which is a product of the breakdown of old red blood cells. Bilirubin happens to be a natural antioxidant: it binds to oxygen free radicals to form biliverdin. Elevated bilirubin can signal an underlying health problem, but in most people, bilirubin is protective. People with low levels of bilirubin are more likely to suffer atherosclerosis and heart disease. C-phycocyanin may help restore the oxidative balance in people with low bilirubin [7, 8, 9, 10, 11].

Other Functional Compounds

Spirulina boasts a range of bioactive compounds like phenols, flavonoids, and polysaccharides. The phenols and flavonoids contribute to this algae’s antioxidant and anti-inflammatory properties; the polysaccharides boost the immune response [1].

Important Nutrients

Dried spirulina is very high in a wide variety of nutrients. 100 g (or about 3.5 oz) of dried spirulina contains more than 100% of the recommended daily intake of total proteins, vitamin B1 (thiamin), vitamin B2 (riboflavin), iron, and copper. It is also a significant source of vitamin E, vitamin K, vitamin B3 (niacin), folate, magnesium, potassium, and manganese [1, 12, 13, 14, 15, 16, 17].

Note that if you are taking a few grams of spirulina as a supplement, these nutrients will probably not be present in high enough quantities to make a real difference in your nutrient status.

Spirulina is Not a Source of Vitamin B12

Spirulina contains inactive compounds called corrinoids, one of which has a structure very similar to vitamin B12. In fact, this corrinoid, which is sometimes called pseudovitamin B12, is so similar to the real thing that researchers cannot tell the difference with conventional lab tests. As a result, some nutrition sources report that spirulina contains large quantities of B12 even though the pseudovitamin corrinoid has no biological activity and cannot be substituted for vitamin B12 [18, 19, 18].

People who eat a vegetarian diet may have difficulty finding plant-based foods containing vitamin B12. This essential vitamin supports the nervous system and bone marrow, and a deficiency can cause low blood cell count or neurological problems [20].

If you are a vegetarian, do not rely on spirulina for vitamin B12. It contains an inactive corrinoid, not the real vitamin.

How Does Spirulina Work?

Antioxidant Activity

Spirulina is a powerful antioxidant. It contains multiple active compounds with antioxidant properties, including phycocyanins, phenols, and flavonoids [1].

Thiobarbituric acid reactive substances, or TBARS, are byproducts of oxidative stress: when reactive free radicals damage tissues, TBARS are released; this makes them useful for measuring oxidative stress. In multiple cell studies, spirulina dramatically decreased the production of TBARS, even when the cells were also exposed to the toxic chemotherapy drug fluorouracil [21].

Innate antioxidant enzymes – such as glutathione peroxidase (GPX), selenium-dependent glutathione peroxidase (GPX-Se), and oxidized glutathione reductase (GR) – defend the body from oxidative stress by converting free radicals into their harmless forms. In a cell study, spirulina protected these enzymes in the presence of high levels of iron [21, 22].

C-phycocyanin is very similar to bilirubin, an antioxidant that forms when red blood cells are broken down. It may block NADPH oxidase, which produces free radicals under stress [7, 23].

Anti-Inflammatory Activity

Tumor necrosis factor (TNF) and interleukin 6 (IL-6) are inflammatory molecules called cytokines. Cyclooxygenase-2 (COX-2) is an enzyme that produces inflammatory compounds. Prostaglandin E2 (PGE2) is a hormone which, among other functions, increases inflammation. In animal models of age-related inflammation, spirulina decreases TNF and IL-6, suppresses COX-2, and reduces PGE2 expression [24].

In rats, spirulina prevents mast cells from releasing histamine, a powerful inflammatory compound [25].

Note that some studies suggest spirulina may increase certain inflammatory cytokines, such as IL-1 from macrophages, as part of its immune-boosting activity. Added together, however, spirulina’s total effect is a decrease in inflammation [26].

Strengthening the Immune System

In animals, spirulina activates multiple branches of the immune system. In mouse studies, polysaccharides from spirulina increased activity in the bone marrow, thymus, and spleen: these structures grow and develop blood cells, and their health is vital to a strong immune system. The reason for this may be that spirulina increases expression of bcl-2, a gene that prevents cells from dying, specifically in these tissues [26].

Phycocyanin from spirulina may boost the activity of erythropoietin, a hormone that increases red blood cells. Though we know them as the oxygen-carrying workhorses of the blood, red blood cells also participate in the immune response: proteins inside them are toxic to bacteria and yeast, and these cells can act as “decoys” for invading viruses. The viruses attack red blood cells instead of other tissues, leaving them vulnerable to white blood cells [26, 27].

C-phycocyanin and spirulina polysaccharides may also increase the production of white blood cells, the most important cells for immunity. In animal studies, spirulina increased the number and activity of macrophages, a type of white blood cell that “eats” bacteria, viruses, and even cancer cells [26, 28, 1, 29].

In cells and animals, spirulina also increased the activity of natural killer cells, which attack viruses and tumors. In multiple studies, animals given spirulina also had increased lymphocyte activity and antibody production [26, 28, 1, 29].

Spirulina may improve the function of immune cells and organs by protecting them from toxins, damage, and environmental stress. In this way, the antioxidant and immune-boosting properties of spirulina may be linked [26].

In short, spirulina triggers a series of changes to the immune and inflammatory responses, reducing overall inflammation while strengthening immunity [26, 1].

Other Mechanisms

Spirulina may have other mechanisms of action which are currently under investigation.

For example, spirulina may prevent harmful mutations in p53, an important gene for preventing tumor growth. And unlike the lipopolysaccharides from bacteria, the ones in spirulina may activate a pathway that decreases certain autoimmune cytokines (IL-17) and increases cancer-fighting ones (IFN-γ) [30, 31].

In multiple cell studies, spirulina prevented a variety of viruses (including HIV) from dividing. Many of these effects have not been investigated in animals or humans; however, in one study, spirulina significantly increased the survival rate of hamsters infected with a deadly herpes virus [26].

Health Benefits of Spirulina

1) Prevents Oxidative Stress

When free radicals build up, they disrupt structures, machinery, and even DNA inside cells. This process is linked to a great many diseases, including cancer, Alzheimer’s disease, Parkinson’s disease, and arthritis [32, 33].

The most robust benefit of spirulina is probably its antioxidant effect. Multiple cell, animal, and human studies have demonstrated its ability to reduce oxidative stress; furthermore, spirulina contains diverse active compounds with antioxidant activity. It may contribute to whole-body health and, when combined with diet and lifestyle choices, delay or prevent disease onset [34, 35, 1].

2) Protects the Heart

A review of human clinical studies suggests that spirulina may protect the heart not only through its antioxidant properties but also by lowering cholesterol, triglycerides, and blood pressure [35].

Blood Pressure

Multiple clinical studies revealed that spirulina lowers blood pressure. In particular, the diastolic blood pressure – the lower of the two numbers, measured when the heart is resting between beats – is significantly decreased in people taking spirulina supplements [36, 37, 35].

Cholesterol and Triglycerides

High levels of cholesterol and triglycerides increase a person’s risk of heart disease and stroke [38, 39, 40].

In animal and human studies, spirulina has decreased total cholesterol, LDL (the “bad” cholesterol), and triglycerides in the blood. These markers may increase as we age; spirulina may, therefore, have key benefits in elderly people or in those prone to high levels [24, 35].

3) Decreases Inflammation

Inflammation, like oxidative stress, is linked to many different conditions. Inflammatory diseases include everything from depression to IBD to arthritis [41, 42, 43].

Spirulina contains multiple bioactive compounds that are known to reduce inflammation. Taken as a supplement, spirulina blocks the activity of molecules that stimulate the inflammatory response. In both human and rat studies, it reversed an age-related increase in inflammatory cytokines [1, 34, 24].

In Allergic Rhinitis

Allergic rhinitis is the most common allergic reaction to environmental allergens like pollen; it is also a major part of asthma. In one clinical study, spirulina decreased all measured symptoms of allergic rhinitis compared to placebo [44, 45].

4) Boosts Immunity

Animal and human studies have demonstrated spirulina’s immune-boosting properties. By activating white blood cells and the tissues that produce them, it may help the body defend against bacteria, viruses, and even tumors without causing excessive inflammation [26].

Researchers have yet to conduct clinical trials demonstrating that spirulina effectively boosts the immune system during infection or disease. However, the results from cell and animal studies and its effects on blood markers in elderly and obese people are promising [1].

5) May Lower Blood Sugar

We need sugar to keep a supply of energy available for our bodies, but high blood sugar can lead to insulin resistance and diabetes. In a review of clinical studies, spirulina significantly reduced fasting blood glucose. Clinical studies suggest it may also increase sensitivity to insulin [35, 34].

However, some researchers dispute the claim that spirulina can lower blood sugar in type 2 diabetes: twelve weeks of spirulina tablets (8 g/day) didn’t change blood sugar levels in a group of diabetic Koreans. Each person’s health status (and possibly race) may affect their response to spirulina [35, 46].

6) May Fight Cancer

Spirulina activates natural killer cells, which improve the body’s immune response to tumors [26].

It may also block tumor development more directly. In one study, rats were dosed with a carcinogenic toxin and either supplemented with spirulina or not. 20% of the rats given spirulina developed tumors, compared to 80% of the control group. In multiple cell and animal studies, spirulina slowed or reversed tumor growth [30, 7, 31].

Furthermore, in a cell study, spirulina was a stronger antioxidant and had more anti-cancer activity than a similar blue-green algae called chlorella [47].

Note, however, that spirulina supplementation had no protective effect and may even increase death rates when combined with the chemo drug fluorouracil, according to one mouse study. The mechanism of spirulina’s anti-cancer effect is still under investigation; it may be subject to drug interactions or only be protective under certain conditions [48].

7) Prevents Fatigue

Spirulina may improve exercise output and prevent fatigue. In a study of adult men, both short- and long-term spirulina supplementation slightly, but significantly improved exercise output and reduced both physical and mental fatigue [49].

In a second, limited study of only nine “moderately trained” adult men, it improved markers of physical endurance. The evidence for this effect is limited, but promising [50].

8) Protects the Brain

Too much iron in the brain increases oxidative stress, damages neurons, and may trigger a cognitive decline. Spirulina’s antioxidant effects may reverse this stress. Likewise, spirulina decreased harmful inflammation in microglial cells, which is thought to underlie diseases like Alzheimer’s [1, 51, 52].

In one study, an extract of spirulina prevented neuron death by increasing a signaling pathway involving BDNF and CREB – both of which protect neurons from damage and maintain brain function and flexibility during stress [53, 54].

In rats with Parkinson’s disease, spirulina decreased cell death of neurons that produce and release dopamine. Researchers have yet to investigate spirulina’s effect in people with Parkinson’s disease; however, there is significant interest in studying phycocyanobilin in Parkinson’s and Alzheimer’s disease [55, 23].

9) Supports Kidney Function

Many commonly-used drugs are excreted by the kidneys. This work taxes the kidneys and exposes them to damage. Similarly, in people with diabetes, the kidneys struggle under an increased oxidative load. Spirulina’s antioxidant properties prevent oxidative stress in the kidney; in animals, spirulina supports the kidneys while they process medication and filter toxins out of the blood [56, 57, 58, 59].

10) Improves Liver Function

In a limited human study of three people, 4.5 g/day of spirulina lowered blood cholesterol and triglyceride levels and improved symptoms of fatty liver disease, indicating it might be helpful in people with this disease [60].

Unsurprisingly, one of the reasons why spirulina may support liver function is tied to its antioxidant property. In diabetic rats, spirulina protects liver tissues against oxidative stress and improves markers of liver function [61].

Spirulina may also protect the liver from damage caused by a high-fat diet, as demonstrated in rats. It may also protect the liver from age-related inflammation by optimizing the gut microbiome [62, 63].

11) Improves Chronic Arsenic Poisoning

Arsenic is an element found naturally in very low levels in the environment and in much higher concentrations in (now banned) pesticides and wood preservatives. In some parts of the world, people are exposed to low levels of arsenic in their drinking water and suffer chronic poisoning as a result [64, 65].

In a human trial, spirulina and zinc supplements improved symptoms of arsenic poisoning. People taking the supplements cleared more arsenic in their urine and had less arsenic in their tissues [65].

In one study, the hexane extract of spirulina cleared almost 90% of arsenic built up in rat liver tissues. A second tissue study suggested it was more effective than the typical (alcohol) extract at removing arsenic. However, this extract is NOT commercially available, as hexane is otherwise toxic to the brain [66, 67, 68].

Limitations and Caveats

While nutrition is generally reported based on 100 g of dried material, most people will never consume that much at a time, and clinical research reflects this. Most clinical studies investigated doses between 2 g and 10 g daily. While the people who traditionally live near Lakes Texcoco and Chad may attest to the safety of much larger quantities of spirulina, modern research has yet to investigate this in human trials.

Many of the health benefits of spirulina have only been tested in cell or animal studies. Given how promising these early studies have been, many more human clinical trials are probably on the horizon which will undoubtedly change our understanding of its mechanisms.

Side Effects & Safety

Spirulina is considered very safe. It was a common food for the Aztecs and in parts of Chad, and it can be consumed in large quantities with few expected side effects. People taking spirulina have rarely reported insomnia and stomach upset; these side effects may or may not have been caused by spirulina [69, 1].

Other rare health problems have been reported in people taking spirulina. These effects include autoimmune skin damage, liver toxicity, and anaphylactic shock. Most people who suffered serious side effects after taking spirulina were also taking another medication for a serious health condition; spirulina may, therefore, interact with some drugs and diseases. If you are taking medication – especially for autoimmune disease, blood pressure, or cholesterol – talk to your doctor before supplementing with spirulina [1].

These side effects could have also been due to supplement contamination.

Allergic Reaction

Some people may suffer an allergic reaction to spirulina. At least two cases have been reported, and in both, the allergy was severe. This reaction is extremely rare, but if you are concerned, you can ask your doctor to check for spirulina allergy [1].


The most significant safety risk for people taking spirulina comes from what else might sneak into the Arthrospira biomass. Some farmed spirulina grows in sealed tanks called bioreactors, but most spirulina is farmed in outdoor ponds, where it is difficult to prevent other bacteria from growing alongside Arthrospira. Some of these other bacteria are human pathogens, and others can produce dangerous toxins that persist in the final product. Choose a high-quality spirulina supplement to avoid these risks [2].


Spirulina is very high in the amino acid phenylalanine, containing between 2.6 and 4.1 g of phenylalanine per 100 g of dried spirulina. For most people, this is a good thing: phenylalanine is required for tissue growth and repair. However, for people with phenylketonuria, or PKU, this can make spirulina dangerous to consume [1, 70].

People with PKU don’t have enough of the enzyme phenylalanine hydroxylase, which normally converts phenylalanine into another amino acid, tyrosine. PKU can be managed through careful diet and supplementation with an amino acid blend. Since spirulina is very high in phenylalanine, people with PKU should completely avoid spirulina [70, 1].

Autoimmune Activation

Spirulina has enough immune-boosting power that it may activate or worsen an autoimmune disorder in people who are prone to such conditions. If you have an autoimmune disorder or if autoimmunity runs in your family, talk to your doctor before supplementing [71, 26].

Drug Interactions

Spirulina probably should not be combined with immunosuppressive drugs or any medication that is metabolized by CYP450 enzymes.


Because spirulina boosts immunity, it may interfere with the effects of drugs that suppress the immune response. Immunosuppressants are usually given after a transplant or graft in order to prevent the body from rejecting its new organ or tissue. They are also used to manage autoimmune disorders like multiple sclerosis, arthritis, and lupus [72, 73, 74].

Immunosuppressive drugs include glucocorticoids like prednisone, cytostatics like azathioprine, drugs that act on immunophilins like cyclosporine, and some other drugs like opioids [73, 75, 76, 77].

If you are taking any medication to suppress the immune response, talk to your doctor before supplementing with spirulina.

CYP Substrates

In rats, spirulina supplements increased and decreased the levels of certain cytochrome P450 (CYP) enzymes. These enzymes break down many drugs and other compounds; spirulina may, therefore, interact with medications that rely on CYP enzymes to break them down and remove them from the body [78, 79, 80].

In rats, spirulina decreased:

  • CYP1A2 activityThis enzyme breaks down a variety of medications, including many antidepressants, some antipsychotics, some painkillers, caffeine, ropivacaine, zolmitriptan, tamoxifen, cyclobenzaprine, propranolol, and warfarin [81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92].
  • CYP2E1 activity: This enzyme breaks down a variety of medications, including anesthetics, acetaminophen (Tylenol), nicotine, ethanol, industrial toxins like benzene, theophylline, chlorzoxazone, and zopiclone [78, 81, 93, 93, 93, 93, 93, 94, 93, 95].

Spirulina also decreased the activity of some other less-known CYP enzymes in rats. But due to the lack of additional research, we do not currently have a complete list of medications that may interact with spirulina [96].

Talk to your doctor before combining spirulina with medication.



People with PKU must have two abnormal alleles for defective phenylalanine hydroxylase at the PAH gene. Any two abnormal alleles can cause the disease, even if the two mutations are at different SNPs. Dozens of different SNP variants can be responsible for PKU; the most common is Arg408Trp, or the T allele at rs5030858 [70, 97].

CYP Genes

Variants in the CYP enzymes mentioned above may change how your body responds to spirulina. Spirulina increases certain CYP enzymes and decreases others. In rats, it decreases the expression of CYP1A2 and CYP2E1. People who already have decreased activity in these enzymes may wish to avoid spirulina, especially if they are taking certain prescription medications [78].

Supplementation & Dosage

Spirulina is available in powder, pill, capsule, and liquid extract. Traditionally, it has also been eaten as a dried “cake.” All spirulina supplements are made from the biomass of the whole organism: spirulina is a cyanobacterium, not a plant [4].

Note that some supplements marketed as “blue-green algae” may be spirulina, but they may also be chlorella or klamath. If you are looking specifically for spirulina supplements, make sure to buy a high-quality supplement that only lists spirulina on the label [98].

Spirulina pills and capsules can be swallowed like any other pill or capsule. The powder and liquid extract can be mixed into drinks, smoothies, yogurt, or other foods.


Clinical studies have used a range of doses to investigate spirulina’s effects. People have seen beneficial effects from as little as 400 mg per day, though most studies used doses of between 2 g and 10 g per day [1].

Toxicological studies show that spirulina is very well tolerated; rats fed spirulina as nearly half of their complete diet had no chronic negative effects. You may wish to start at a lower dose and increase it slowly [99].

Pet Food Supplement

As more and more people move away from commercial kibble diets for their pets, pet owners are looking for nutritious supplements and additives to keep their dogs and cats in top condition. Spirulina is a popular supplement for pets on a homemade raw diet [100, 101, 102].

Only one study has ever investigated the effect of spirulina on dogs; this study found that spirulina polysaccharides protected the bone marrow from damage caused by chemo- and radiotherapies. In one cat study, spirulina increased the activity of immune cells. Because of its excellent safety profile and history of animal feeding, spirulina is considered safe to feed to dogs and cats [103, 104, 26, 105].

In dog diets, spirulina is used as a source of vitamins, iodine, and trace minerals. It should only be used as a supplement and not as a primary protein source [105].

User Experiences

Most online user reviews for spirulina supplements are positive. People report having more energy, lower cholesterol, increased physical performance, and fewer infections. Some people reported side effects, including nausea, indigestion, heartburn, and migraine. Of these, some admitted that these side effects may have been caused by other medication or foods, or by underlying physical conditions.

Buy Spirulina


Spirulina is the dried product of two species of cyanobacteria, or blue-green algae. It has been a staple food for people living around Lakes Texcoco and Chad for centuries; the health effects of its active phycocyanins, phenols, and polysaccharides more recently made it a popular supplement. It is also a safe supplement for pets and a good feed for livestock animals.

Spirulina has significant antioxidant, anti-inflammatory, and immune-boosting effects. It lowers blood pressure, blood sugar, cholesterol, and triglycerides and may prevent certain types of allergic reactions. It may also fight cancer and protect the brain, kidneys, and liver. Some studies suggest that it may be used to manage chronic arsenic poisoning.

Low-quality spirulina supplements may be contaminated with harmful bacteria or toxins. Very rarely, people have had serious allergic reactions to spirulina; it has also activated or worsened autoimmunity in sensitive people. People with phenylketonuria or anyone taking immunosuppressive or CYP-metabolized drugs should avoid spirulina.

Spirulina is available as a powder, capsule, pill, or tincture. As little as 400 mg per day may be effective, but most clinical studies used between 2 and 10 g per day.

About the Author

Jasmine Foster, BSc, BEd

BS (Animal Biology), BEd (Secondary Education)

Jasmine received her BS from McGill University and her BEd from Vancouver Island University.

Jasmine loves helping people understand their brains and bodies, a passion that grew out of her dual background in biology and education. From the chem lab to the classroom, everyone has the right to learn and make informed decisions about their health.

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