What Is Spirulina?

This blue-green algae's been studied for blood sugar control... and more

Spirulina tablets and powder in bowls
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Spirulina is a blue-green algae from the genus Arthrospira ("arthro" roughly meaning "joint," and "spira" meaning "spiral"). It's been used by the Aztecs in Mexico and people living in the Lake Chad area in Africa for centuries. Spirulina's usually cultivated from bodies of water like lakes or farmed in ponds.

Spirulina contains several nutrients, including fat-soluble vitamins (A, E, and K), fatty acids (DHA, EPA), beta carotene and minerals. It's also a source of protein, but it lacks high enough levels of some of the amino acids that your body needs to function at its best (unless you have a medical condition where you need to avoid specific amino acids, like with phenylketonuria or "PKU"). Since spirulina comes from bacteria (specifically "cyanobacteria"), it may be considered a protein source for vegans.

It's also important to note that the B12 in spirulina is in a different form as "pseudovitamin B12" than the type typically absorbable by your body. You'll likely need to look elsewhere for your B12 needs, especially if you follow a vegetarian or vegan way of eating , which can be low in B12. Lower levels of B12 are also found in adults over the age of 60 years. And why's B12 important? Because your body needs B12 to make red blood cells, and it's also crucial for brain and nerve cell development. Not getting enough B12 can cause tiredness, memory loss, depression, and even different types of anemia. But we digress.

This article takes a closer look at the potential uses of spirulina. It also covers risks associated with its use.

Dietary supplements are not regulated in the United States, meaning the FDA does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF. However, even if supplements are third-party tested, that doesn’t mean that they are necessarily safe for all or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

  • Active Ingredient(s): Phycocyanins, fatty acids, protein, vitamins, minerals
  • Alternate Name(s): Blue-green algae, dihé (Chadic language, Africa), tecuitlatl (Aztec)
  • Legal Status: “Grandfathered” dietary ingredient (legally marketed before 1994)
  • Suggested Dose: 1g/day (six months) to 19g/day (two months) have been used in clinical trials. However, there is no official suggested dosage for spirulina.
  • Safety Considerations: Allergy, heavy metals (lead, cadmium, arsenic, mercury), toxins (microcystins, other cyanobacteria)

Uses of Spirulina

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian nutritionist (RD/RDN), pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease.

Spirulina has fat-soluble vitamins (like A, E, and K), beta carotene and minerals, protein, and phycocyanins (pigments that produce a blue color and that have shown antioxidant effects). Phycocyanins have been used as a dye in many industries, including pharmacy, culinary, and even cosmetics.

Scientists have studied - but not necessarily proven - spirulina's impact on different areas of health, including but not limited to:

We'll explore what the science says about spirulina's effectiveness for these health outcomes.

Antioxidant capacity

According to a meta-analysis (a collection of research studies) of nine studies with a total of 415 people, spirulina increased superoxide dismutase (SOD) and total antioxidant capacity (TAC). The studies used anywhere from one to eight grams of spirulina per day, a pretty extensive range. Many of the studies had a relatively small number of people, meaning they might not be able to tell us very much. The strength of the effects was not earth-shattering and was generally more substantial when people took five grams of spirulina per day or more.

The conclusion? Getting antioxidants from the foods that we eat can help reduce some of the inflammation in our bodies. To amp up antioxidants in your diet, try including a variety of the most nutrient-dense foods that you can source and afford - and they don't have to be organic - like whole grains, fruit, and vegetables to help increase your body's antioxidant capacity and reduce inflammation in your body. Just don't rely on spirulina alone.

Blood pressure

Scientists did a meta-analysis (a collection of several research studies on a topic) of five randomized controlled trials that included 230 people to check spirulina's effects on blood pressure. The people in the different studies took anywhere from one to eight grams a day of spirulina (a pretty big range). The lengths of the studies were anywhere from two to 12 weeks. And many of the studies were pretty small, meaning they really might not be able to tell us very much.

When the data was "pooled" (put together) and analyzed from these studies, the scientists said that the spirulina lowered systolic blood pressure by about 4.59 mmHg and also diastolic blood pressure by 7.02 mmHg. Systolic pressure (top number) measures the pressure in your arteries when your heart beats. Diastolic pressure (bottom number) measures the pressure your arteries experience between each heartbeat. The biggest blood pressure-lowering in the studies was seen in people who had high blood pressure already. Makes sense.

The scientists also said more, high-quality studies are needed before we can start recommending that everyone with high blood pressure needs to start eating spirulina. Fair enough. Next!

Blood sugar control

Have you ever gotten a jittery feeling after eating sugary food? That usually means your blood sugar's spiking. And this situation can be dire for people coping with conditions like type I or type II diabetes, disordered eating including diabulimia, and more.

Over time, blood sugar spikes that are left uncontrolled can actually lead to damage to your body. Worst case, in certain conditions like diabetes, that can look like having to surgically remove parts of your body (amputation), heart attacks, kidney failure, or stroke which can lead to paralysis of parts of your body. While spirulina really would not likely be able to the correct severe damage from uncontrolled blood sugar over time by itself, it has lowered blood sugar levels in human studies. And why? It could be its protein and fiber content, or perhaps it is phycocyanin's ability to help with inflammation. Scientists are still figuring it out.

Fourteen studies with 510 people with metabolic syndrome - a collection of symptoms like high blood sugar, high blood pressure, high triglycerides, low HDL ("good cholesterol"), and high waist circumference which all together can create more serious health problems - were included in a meta-analysis of spirulina's effects on blood sugar and other outcomes. And a lot of those studies didn't have many people in them (they had "lower statistical power"). People took anywhere from one to eight grams of spirulina per day (again, that's a pretty big range). Blood sugar and insulin levels were reduced in some of the studies after taking specific amounts of spirulina. More, high quality studies are needed before we can recommend spirulina for lowering blood sugar and insulin levels.

Generally, working with a team that includes a registered dietitian nutritionist (RD or RDN) - and particularly one that's a Certified Diabetes Care and Education Specialist (CDCES) - can help you explore your eating, movement, medication habits and more. RDs/RDNs can help you build your toolkit and your capacity to avoid spikes in your blood sugar. That could help you feel better. Managing blood sugar can be challenging and we don't have to do it alone!

Cancer

Sorry folks, there're very few, well-conducted human studies that have looked at spirulina's effects on cancer. There've been several studies in test tube cells or in animals that aren't humans. While that's really interesting "preliminary" information (a place to start), if there aren't well-constructed studies looking at its effects in humans, we can't really make any assumptions about its effects on our species.

Cholesterol levels

Scientists conducted a meta-analysis of spirulina's effects on cholesterol levels that had seven controlled trials for a total of 522 total people. They found that spirulina reduced: total cholesterol (by 46.76 mg/dL), low density lipoprotein ("LDL" by 41.32 mg/dL), and triglycerides (by 44.23 mg/dL). It also increased the "good" cholesterol or high-density lipoprotein ("HDL" by 6.06 mg/dL). Again, why did spirulina do this? We're not sure, but scientists think it may be due to its nutritional profile (fiber, fatty acids like DHA and EPA), its antioxidant capacity, or a combination of these.

While we can't recommend spirulina for lowering your cholesterol, we can suggest working with a team that includes a registered dietitian nutritionist (RD or RDN) that can help you explore your eating patterns, movement, and more. Registered dietitian nutritionists can help you build your toolkit and your capacity. Again, you're not alone!

Liver health

Spirulina has been studied for its effects on liver health in people with nonalcoholic fatty liver disease (NAFLD). However, the study was very small (only 13 people), so we can't draw any conclusions about spirulina for NAFLD until larger and better studies are done.

Metabolic syndrome

Scientists have studied spirulina's effects on metabolic syndrome. Metabolic syndrome happens when you have high blood pressure, high blood sugar, high cholesterol, and excess fat around your waist (excess abdominal fat). Metabolic syndrome can wreak havoc with your health and increases your odds of heart attack, stroke, and type two diabetes. One of metabolic syndrome's main causes is thought to be obesity. Obesity, however, can also be connected to a host of other social, economic, and environmental causes (aka, "determinants of health"). Furthermore, its definition is based on a metric that's thought to be flawed (Body Mass Index, or BMI). It's important to note that BMI does not necessarily take into account important body composition factors like frame size and muscle mass.

One spirulina meta-analysis pulled together data from 18 studies. It suggested that spirulina could help lower high blood pressure, high blood sugar, and high cholesterol - all parts of metabolic syndrome. It's important to note that while spirulina may impact these outcomes, the most essential issue would be working on your current way of eating, your movement (exercise), and other equally important issues like addressing your emotional health. Spirulina can't solve these serious issues.

Consider working with a team that includes a registered dietitian nutritionist (RD or RDN) - and perhaps one that's a Board Certified Specialist in Obesity and Weight Management (CSOWM). RDs/RDNs can help you explore your eating, movement, medication habits, and more. They can help you build your toolkit and your capacity to help you feel better. Sometimes it can be challenging to give yourself permission to ask for and accept help. But you've got this. And you don't have to go at it alone.

Obesity

In a meta-analysis of five studies, scientists looked at spirulina's effects on weight management in people coping with obesity. Spirulina did decrease weight in people with obesity by 4.55 pounds (2.06 Kg) and in people who were overweight by 2.82 pounds (1.28 kg). However, clinically speaking, this is not enough to make a solid recommendation for use of spirulina for obesity treatment.

As mentioned previously, it's important to note that obesity can also be connected to a host of other social, economic, and environmental causes (aka, "determinants of health"). Furthermore, its definition is based on a metric that's thought to be flawed (Body Mass Index, or BMI). It's important to note that BMI does not necessarily consider important body composition factors like frame size and muscle mass. And BMI definitely does not give the complete picture of an individual's wellbeing. Consider requesting a body composition test (for example, skin-fold measurements or a DEXA Body Composition scan) from your healthcare provider in addition to other parameters that they may measure.

As mentioned above, consider working with a team that includes a registered dietitian nutritionist (RD or RDN) - and ideally, one that's a Board Certified Specialist in Obesity and Weight Management (CSOWM). CSOWM RDs/RDNs can help you explore your eating, movement, medication habits, and more. They can help you build your toolkit and your capacity, and help you feel better. You've got this.

What Are the Side Effects of Spirulina?

An allergic reaction may be possible in those allergic to spirulina. Allergic reactions would include rash or swelling. Immediately stop using spirulina if you begin to experience side effects and call your healthcare provider.

Common Side Effects

Spirulina is generally safe, but some people have reported the following with its use:

  • Allergy
  • Headache
  • Muscle pain
  • Sweating
  • Trouble sleeping

Severe Side Effects

While severe side effects from spirulina are rare, be aware that the following have occurred:

  • Anaphylaxis (severe allergic reaction)
  • Throat swelling

Immediately stop using spirulina if you begin to experience severe side effects and call your healthcare provider.

Precautions

People with phenylketonuria (inability to process the amino acid, phenylalanine) and individuals with other amino acid disorders - for example, classical homocystinuria (HCU), or maple syrup urine disease (MSUD) - may need to avoid spirulina due to its high protein and thus amino acid content.

The safety of spirulina in pregnant or nursing people has not been established. Speak with your healthcare provider before using spirulina if you're pregnant, plan to get pregnant or if you're breastfeeding.

Please don't give children supplements - including spirulina - without first discussing this with their pediatrician.

Spirulina can sometimes be contaminated with things like lead or other heavy metals (it grows in lakes, after all) or even toxins.

Dosage: How Much Spirulina Should I Take?

Always speak with your healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

Manufacturer recommendations might vary. As a general guideline though, don't use more than what's listed on your product's label. There's no recommended "effective" dosage of spirulina. Avoid spirulina if you're allergic or sensitive to it or any of its ingredients.

Studies have used from one to 10 grams a day for up to six months to 19 grams of spirulina a day for up two months, with a relatively good safety profile in people with different conditions.

Again, please do not give supplements to children without first discussing this with their pediatrician.

What Happens If I Take Too Much Spirulina?

An upper limit or recommended intake is lacking for spirulina. Taking upwards of 40 grams per day for an unknown period of time has been noted. If you believe that you've taken too much spirulina, contact your healthcare provider for information.

Interactions

Blood thinners: While there are only about 0.26 micrograms of vitamin K in each gram of spirulina, taking far larger amounts could theoretically impact the blood-thinning effects of some medicines like Jantoven (warfarin).

Immunomodulators: Little evidence exists to support avoiding the use of spirulina with immunosuppressive drugs or drugs that change the way that the immune system works (immunomodulators).

It is essential to carefully read the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications.

How to Store Spirulina

Store spirulina in a cool, dry place. Keep spirulina away from direct sunlight. Discard as indicated by the "use by" date on the packaging. Keep away from children and pets.

Similar Supplements

Chlorella (a green algae supplement) is somewhat similar to spirulina.

Frequently Asked Questions

  • Is spirulina the same as chlorella?

    No, chlorella and spirulina are different species of algae, but they're both supplements.

  • What antioxidants does spirulina have?

    Spirulina has phycocyanins.

  • If I'm a vegan, can I get all my protein and B12 needs from spirulina?

    While spirulina has most of the amino acids that your body needs, it doesn't have enough of some of them. Try to eat a balanced, varied diet to meet your unique protein needs. The B12 in spirulina - pseudovitamin B12- is in a different form than the type that's typically absorbable by your body. You'll likely need to look elsewhere for your B12 needs.

Sources of Spirulina & What To Look For

Blue-green algae species used in spirulina supplements are typically Spirulina maxima, Spirulina platensis, or Aphanizomenon flos-aquae.

Just because a remedy is thought to be "natural" does not mean that it is safe. Some "wild-crafted" spirulina products may have been grown in water contaminated with heavy metals (mercury, lead, arsenic, cadmium) or other pollutants. Opt for supplements produced in labs and certified by third-party authorities like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

As with all supplements, it's essential to talk with your healthcare provider before using spirulina to decide if it's right for you.

Spirulina Supplements

Spirulina is often sold as a powder. It's also available in capsule, tablet, and liquid form.

Originally written by
Cathy Wong
Cathy Wong

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

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  1. Marles RJ, Barrett ML, Barnes J, et al. United states pharmacopeia safety evaluation of spirulinaCritical Reviews in Food Science and Nutrition. 2011;51(7):593-604.

  2. Watanabe F, Takenaka S, Kittaka-Katsura H, Ebara S, Miyamoto E. Characterization and bioavailability of vitamin b12-compounds from edible algaeJournal of Nutritional Science and Vitaminology, J Nutr Sci Vitaminol. 2002;48(5):325-331.

  3. Shipton MJ, Thachil J. Vitamin B12 deficiency – a 21st century perspective. Clin Med (Lond). 2015;15(2):145-150. doi:10.7861/clinmedicine.15-2-145

  4. Baltrusch S. The Role of Neurotropic B Vitamins in Nerve RegenerationBiomed Res Int. 2021;2021:9968228. Published 2021 Jul 13. doi:10.1155/2021/9968228

  5. Ramadan EF, Grisdale M, Morais M. Maternal Vitamin B12 Levels During Pregnancy and Their Effects on Maternal Neurocognitive Symptoms: A Systematic ReviewJ Obstet Gynaecol Can. 2022;44(4):390-394.e3. doi:10.1016/j.jogc.2021.11.017

  6. Wang Z, Zhu W, Xing Y, Jia J, Tang Y. B vitamins and prevention of cognitive decline and incident dementia: a systematic review and meta-analysisNutr Rev. 2022;80(4):931-949. doi:10.1093/nutrit/nuab057

  7. Spirulina. In: Drugs and Lactation Database (LactMed). Bethesda (MD): National Library of Medicine (US); June 21, 2021.

  8. Yousefi R, Saidpour A, Mottaghi A. The effects of Spirulina supplementation on metabolic syndrome components, its liver manifestation and related inflammatory markers: A systematic reviewComplement Ther Med. 2019;42:137-144.

  9. Romay C, González R, Ledón N, Remirez D, Rimbau V. C-phycocyanin: a biliprotein with antioxidant, anti-inflammatory and neuroprotective effectsCurr Protein Pept Sci. 2003;4(3):207-216.

  10. Serban MC, Sahebkar A, Dragan S, et al. A systematic review and meta-analysis of the impact of Spirulina supplementation on plasma lipid concentrationsClin Nutr. 2016;35(4):842-851.

  11. Karkos PD, Leong SC, Karkos CD, Sivaji N, Assimakopoulos DA. Spirulina in clinical practice: evidence-based human applications. Evid Based Complement Alternat Med. 2011;2011:531053. doi:10.1093/ecam/nen058

  12. Naeini F, Zarezadeh M, Mohiti S, Tutunchi H, Ebrahimi Mamaghani M, Ostadrahimi A. Spirulina supplementation as an adjuvant therapy in enhancement of antioxidant capacity: A systematic review and meta-analysis of controlled clinical trialsInt J Clin Pract. 2021;75(10):e14618.

  13. Machowiec P, Ręka G, Maksymowicz M, Piecewicz-Szczęsna H, Smoleń A. Effect of spirulina supplementation on systolic and diastolic blood pressure: systematic review and meta-analysis of randomized controlled trialsNutrients. 2021;13(9):3054.

  14. Hamedifard Z, Milajerdi A, Reiner Ž, Taghizadeh M, Kolahdooz F, Asemi Z. The effects of spirulina on glycemic control and serum lipoproteins in patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trialsPhytother Res. 2019;33(10):2609-2621.

  15. Silva MROB da, M. da Silva G, Silva ALF da, Lima LRA de, Bezerra RP, Marques D de AV. Bioactive compounds of arthrospira spp. (Spirulina)With potential anticancer activities: a systematic reviewACS Chem Biol. 2021;16(11):2057-2067.

  16. Mazokopakis EE, Papadomanolaki MG, Fousteris AA, Kotsiris DA, Lampadakis IM, Ganotakis ES. The hepatoprotective and hypolipidemic effects of Spirulina (Arthrospira platensis) supplementation in a Cretan population with non-alcoholic fatty liver disease: a prospective pilot studyAnn Gastroenterol. 2014;27(4):387-394.

  17. Moradi S, Ziaei R, Foshati S, Mohammadi H, Nachvak SM, Rouhani MH. Effects of Spirulina supplementation on obesity: A systematic review and meta-analysis of randomized clinical trialsComplement Ther Med. 2019;47:102211.

  18. Matthews J, Herat L, Rooney J, Rakoczy E, Schlaich M, Matthews VB. Determining the role of SGLT2 inhibition with Empagliflozin in the development of diabetic retinopathyBiosci Rep. 2022;42(3):BSR20212209.

  19. Nielsen CH, Balachandran P, Christensen O, et al. Enhancement of natural killer cell activity in healthy subjects by Immulina®, a Spirulina extract enriched for Braun-type lipoproteinsPlanta Med. 2010;76(16):1802-1808. doi:10.1055/s-0030-1250043

  20. U.S. Department of Agriculture. Spirulina.

  21. Bito T, Okumura E, Fujishima M, Watanabe F. Potential of chlorella as a dietary supplement to promote human healthNutrients. 2020;12(9):2524.