Spirulina Benefits: Detox, Nutrition, Dosage & Side Effects

Stir a spoonful of spirulina into a glass of water and it turns a deep blue-green. Under a microscope, that powder is a tangle of tiny spiral filaments, a microbe that people living around Lake Texcoco in Mexico and Lake Chad in Africa harvested, dried into cakes and ate long before anyone sold it in a jar.7 A level tablespoon supplies 4 grams of protein for about 20 calories.1

Spirulina does two jobs in my approach. It's a nutrient-dense whole food, and it helps your body clear heavy metals. In Heal Your Cells, Dr. Will Cole and I list spirulina or chlorella in our liver protocol because it binds heavy metals and supports detox.2

Blue-green algae, the group spirulina belongs to, has a place in my own family's story. During my mom's recovery from cancer, which came through nutrition and lifestyle alongside her medical care, blue-green algae was one of the things she took every day, along with turmeric, ginger and reishi mushrooms and a very clean diet.8

Did you know?

• Spirulina is named for its shape, tiny spiral-coiled filaments. Botanists later renamed it Arthrospira, from the Greek words for "joint" and "spiral."7

• Growers keep spirulina's water at a pH of about 9 to 11, strongly alkaline, because that keeps other algae from moving into the culture.9

• In a study of 14 men with no comparison group, a single 4- to 5-gram serving of spirulina eaten with some fat more than doubled blood levels of zeaxanthin, a pigment concentrated in your eyes.10 Our guide to lutein covers its partner pigment.

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What is spirulina?

On my show, I've pointed out that most people think of spirulina as more of a vegetable, when it's really more of a microbe.8 Each spirulina filament is a chain of cells coiled into a spiral, and the commercial strains come mostly from highly alkaline waters in tropical and subtropical regions.7 It's often sold and studied alongside other algae and seaweeds such as kelp and nori.

Spirulina packs a lot into a small amount: protein, iron, copper and B vitamins in a few grams, as the nutrition section below shows. Our guide to nutrient-dense foods covers other foods that do the same.

A short history of spirulina

Spirulina fed people long before it was a supplement. The Aztecs and other peoples of Mexico ate it until the 16th century, and a Spanish chronicle from 1521 describes harvesting it from Lake Texcoco and selling it as blue-green cakes called tecuitlatl.7 Half a world away, people living near Lake Chad in Africa made dried cakes of it called dihé, and in 1940, a sample of one of those cakes brought spirulina back to scientists' attention.7 The two cultures discovered this food independently, and today spirulina is produced in at least 25 countries.7

Spirulina vs. chlorella

Spirulina and chlorella are often sold together, and they're different organisms: spirulina is a cyanobacterium and chlorella is a microalga.11 I recommend both as gentle binders, and my parasite and candida protocols use chlorella as a light binder.21213 This page covers spirulina's own research, and our chlorella guide covers chlorella's.

Spirulina nutrition facts

Values from USDA FoodData Central, FDC ID 170495 (seaweed, spirulina, dried, SR Legacy). Per-serving amounts are calculated from the per-100-gram values; % Daily Value uses FDA label reference values.1

A few grams of spirulina makes its biggest contribution in copper, riboflavin and thiamin, plus a useful amount of protein for so few calories.1 The record dates from older USDA analyses, and a 2024 review notes that spirulina's makeup varies by manufacturer, so treat these as typical values.7

Is spirulina a good source of protein?

Yes. Protein makes up more than half of dried spirulina by weight,1 and a 2023 review gives its protein a biological value of 75, a measure of how much of the protein your body can put to use.9 In a randomized trial of 36 young adults, the 12 who drank 25 grams of protein from spirulina saw blood amino acids rise quickly and muscle-building rates increase both at rest and after a strength workout.11 At everyday doses, spirulina adds a few grams of protein to your day, so pair it with complete proteins and other plant-based protein foods at meals.

Does spirulina have vitamin B12?

For vitamin B12, look to animal foods or a supplement. In a lab analysis of spirulina tablets, most of the B12-like compounds were inactive; of the two that bind your body's B12 carrier, 83% was pseudovitamin B12, an inactive form, and 17% true vitamin B12.14 USDA lists 0 micrograms of B12 in dried spirulina.1 As I explained in a 2024 episode of my show, "If you're a vegan or a vegetarian, you almost always want to supplement with a B complex or a B12 supplement."15 Eggs and wild-caught fish are good everyday sources; see the top vitamin B12 foods.

Does spirulina have iron?

A tablespoon of dried spirulina carries 2 milligrams of iron,1 and in trials it raised serum iron and hemoglobin, as the benefits section below shows.2425 How much you get from a product varies widely: in a 2022 test of supplements sold in Slovenia, a recommended dose supplied anywhere from 7.64% to 316% of the recommended daily iron intake, much of it in the ferric form, which your body absorbs less easily.16 Check the label of the one you buy for its iron per serving.

What is spirulina good for?

How does spirulina work in your body?

Research points to three ways spirulina works: it carries compounds that act on blood vessels, it supports your own antioxidant defenses, and it turns up parts of your immune system.

• Acts on blood vessels. In lab digestion tests, plain spirulina released small peptides that block ACE, the enzyme many blood pressure drugs target.31 In a placebo-controlled pilot trial of 16 adults with high blood pressure who were already taking ACE-inhibitor medicine, 4.5 grams a day of Spirulina maxima for 12 weeks lowered systolic pressure and markers of damage to the blood vessel lining.32

• Supports antioxidant defenses. In 9 trained men who each tried spirulina and a placebo for 4 weeks, 6 grams a day raised glutathione, an antioxidant your cells make, at rest and the day after hard exercise.27

• Turns up immune activity. In a study of volunteers tested before and after taking a hot-water extract of spirulina, with no comparison group, natural killer cells, front-line immune cells, made more interferon and killed more target cells in more than half of them.33 That immune-activating effect is also why the safety section asks people with autoimmune conditions to be careful.

What are the benefits of spirulina?

Clearing heavy metals leads this list because that's the job spirulina does in my liver protocol. Then come weight, blood pressure, blood sugar, cholesterol, inflammation and energy and nasal allergies.

More research: iron, endurance and mouth health

Spirulina supplies iron, and trials have measured what it does for your blood. In a placebo-controlled trial of 80 adults with ulcerative colitis (73 finished), 1 gram a day for 8 weeks raised serum iron compared with placebo.24 In 17 recreationally active adults who each tried spirulina and a placebo for 14 days, 6 grams a day raised hemoglobin to 15.04 g/dL, against 14.56 g/dL on placebo, though endurance and power didn't change.25 In 30 adults over 50 with a history of anemia who finished a 12-week study without a comparison group, the hemoglobin content of red blood cells rose in both men and women.26

Endurance athletes have tested it too, with mixed results across four small trials:27252928

For more, see our guide to supplements for athletes.

The longest trial on this page looked at the mouth. In a placebo-controlled trial in Kerala, India, tobacco chewers with leukoplakia, white patches in the mouth that can become cancerous, took 1 gram a day of Spirulina fusiformis or a placebo for 12 months. The patches cleared completely in 20 of 44 people on spirulina (45%), against 3 of 43 on placebo (7%); they returned in 9 of the 20 within a year of stopping, and spirulina caused no toxicity.30

Can spirulina help your body clear heavy metals?

Your body does its own detox work: cellular detoxification happens deep in your liver, in a two-step process, and mercury, lead, arsenic and cadmium turn up in everyday sources such as tap water, farmed fish, canned goods and dental fillings, then build up and disrupt your mitochondria and your body's detoxification over time.2

The first step is lowering what comes in, and that starts with clean water: a high-quality water filter that removes heavy metals, PFAS, fluoride, chlorine and pharmaceutical residues.2 The Bangladesh trial below worked the same way: every household in both groups got an arsenic-removing water filter, so spirulina's effect was measured on top of clean water.17

Next, to help your body detoxify, I recommend eating steamed vegetables on a regular basis, along with spirulina, chlorella, probiotics and chlorophyll, which all help bind and eliminate heavy metals.48 My parasite protocol adds cilantro and parsley for heavy metals.12

Here's how the research fits together, step by step:

The Bangladesh trial is the main human study. Researchers gave 24 adults with chronic arsenic poisoning from well water 250 milligrams of a spirulina extract plus 2 milligrams of zinc twice a day for 16 weeks, and gave 17 others a placebo; neither the people nor the researchers knew who got what. Before the filters went in, the spirulina group's urine carried 78.4 micrograms of arsenic per liter, and after 2 weeks of filtered water it dropped to 21.6. Then, at 4 weeks of spirulina extract plus zinc, urinary arsenic jumped to 138 and stayed up for another 2 weeks, meaning more arsenic was leaving the body. By the end, arsenic in scalp hair had fallen 47.1%, and the darkened and thickened skin patches of arsenic poisoning improved on spirulina and zinc but not on placebo, with no major side effects.17

Binders trap everything indiscriminately, so in my protocols they go two hours away from food, herbs, supplements and medications.12 With the gentler, more natural binders, I'd take them first thing in the morning, between meals or right before bed.53 Some of the gentler binders can go with a meal,53 so a scoop of spirulina in your breakfast smoothie is fine as a food; when binding heavy metals is the goal, take it on its own. Our heavy metal detox guide covers the other steps, including fulvic acid and pectin.

How much spirulina should you take a day?

A level tablespoon of dried spirulina weighs 7 grams, so a teaspoon is a little over 2 grams, and 3 to 5 grams is roughly 1 1/4 to 2 teaspoons of powder.1 With tablets, check the milligrams on the label: six 500-milligram tablets make 3 grams. A 2023 review puts the recommended adult intake at about 3 to 10 grams a day.9 Start at 1 gram a day, the lowest daily amount of whole spirulina the trials used, and work up to your full amount.3544

How to take spirulina

Spirulina tastes strong and a little like the sea, so it's easiest blended into a drink or swallowed as tablets. I recommend a daily superfood powder as an insurance policy, because many of us aren't getting enough berries and vegetables, and spirulina is one of the superfoods that fits that role.56

How to choose a spirulina supplement

Spirulina picks up what's in its water, so where it comes from matters. Use this checklist when you buy:

• Spirulina named on the label, as Arthrospira platensis or Arthrospira maxima, with grams per serving

• Cultivated spirulina: phycocyanin from cultivated spirulina carried less arsenic and lead than phycocyanin from cyanobacteria collected in the wild49

• Third-party tested for microcystins and heavy metals, with results the maker will share

• Testing over the organic label alone: in 52 spirulina and chlorella products, organic and conventional versions didn't differ significantly in contaminants50

• Stored sealed, cool and dry, following the label once opened

Spirulina side effects and who should skip it

The concern with spirulina is what can get into it. Spirulina is often grown in open ponds, where other cyanobacteria, including toxin-making ones, can move in.60 Some of those make microcystins, toxins that can damage the liver.61 In a test of 18 algae supplements, 14 of them spirulina, 4 carried microcystins above the World Health Organization's tolerable daily intake at their highest labeled dose: one spirulina product and three made from another blue-green alga, Aphanizomenon flos-aquae,62 and a Greek study found microcystins in all 5 retail spirulina products it tested, a powder, tablets and three spirulina-enriched foods, at levels that could push someone past the recommended daily limit.60 Metals depend on the water too: all 52 spirulina and chlorella products in a 2025 analysis met EU limits for toxic metals, though some carried traces of medication residues.50 The buying checklist above is how you stay on the safe side.

Here's who should skip spirulina or check with a practitioner first:

• Phenylketonuria (PKU). Spirulina is a protein food: 5 grams supplies about 139 milligrams of phenylalanine, the amino acid people with PKU must strictly limit, so skip it.1

• Autoimmune conditions. Spirulina turns up immune activity,33 and in a report of three patients, pemphigus vulgaris or dermatomyositis flared after immune-stimulating supplements, spirulina products among them.63 With an autoimmune disease, skip it unless the practitioner managing your condition agrees.

• Pregnancy and nursing. None of the trials on this page enrolled pregnant or nursing women, and tested spirulina products have carried microcystins, liver toxins, at levels that reach or pass the daily safety limit,6260 so skip spirulina unless your OB confirms it's right for you.

• Allergy. Reactions to spirulina are uncommon, but a 2024 review found five documented patients, four of them with anaphylaxis.46 Stop at any itching or hives, and get emergency help for wheezing, trouble breathing or swelling of the lips, tongue or throat.

The bottom line

Spirulina: frequently asked questions

References

1. U.S. Department of Agriculture, Agricultural Research Service. Seaweed, spirulina, dried. FoodData Central, SR Legacy, FDC ID 170495 (NDB 11667).
2. Axe J, Cole W. Heal Your Cells. Avery; 2026. ISBN 9798217181353 ("Precision Healing Protocols," liver supplement list, item 6 "Spirulina/chlorella": binds heavy metals, supports detox, 3–5 g/day powder or capsules, p. 344; cellular detoxification in the liver's two-step process; everyday heavy-metal exposures; "Reduce toxic input": a high-quality water filter that removes heavy metals, PFAS, fluoride, chlorine and pharmaceutical residues).
3. Shahinfar H, Jayedi A, Torabynasab K, et al. Comparative effects of nutraceuticals on body weight in adults with overweight or obesity: A systematic review and network meta-analysis of 111 randomized clinical trials. Pharmacol Res. 2023;196:106944. doi:10.1016/j.phrs.2023.106944
4. Shiri H, Yasbolaghi Sharahi J, Alizadeh Sani M, et al. The Effect of Spirulina Supplementation on Blood Pressure in Adults: A GRADE-Assessed Systematic Review and Meta-Analysis of Randomized Clinical Trials. Phytother Res. 2025;39(1):397-412. doi:10.1002/ptr.8377
5. Shiri H, Soleimani AA, Omidi Sarajar B, et al. Spirulina's impacts on cardiovascular health: Insights from a systematic meta-analysis of RCT. Complement Ther Med. 2025;94:103242. doi:10.1016/j.ctim.2025.103242
6. Nourollahian M, Rasoulian B, Gafari A, et al. Clinical comparison of the efficacy of spirulina platensis and cetirizine for treatment of allergic rhinitis. Acta Otorhinolaryngol Ital. 2020;40(3):224-229. doi:10.14639/0392-100X-N0139
7. Sinetova MA, Kupriyanova EV, Los DA. Spirulina/Arthrospira/Limnospira-Three Names of the Single Organism. Foods. 2024;13(17):2762. doi:10.3390/foods13172762
8. Axe J. NATURALLY Activate Stem Cells (IMPORTANT if you're over 40). The Dr. Josh Axe Show, YouTube. 2026 (Dr. Axe speaking: spirulina as a microbe at 11:48-12:04; his mom's daily blue-green algae during her 2006 recovery at 22:35-23:24).
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10. Yu B, Wang J, Suter PM, et al. Spirulina is an effective dietary source of zeaxanthin to humans. Br J Nutr. 2012;108(4):611-9. doi:10.1017/S0007114511005885
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12. Axe J. Heal From Parasites Protocol. DrAxe.com. 2025 (Bind phase: "Take binders 2 hours away from food, herbs, and supplements"; Avoid: "Taking binders with food, supps, or meds"; chlorella in the afternoon; cilantro and parsley for heavy metals).
13. Axe J. The Candida Cleanse Protocol: The 30-Day Healing Protocol. DrAxe.com. 2026 (p. 21, Supplements: chlorella plus modified citrus pectin, 2–3 g plus 5 g daily, "Two hours from food and supplements").
14. Watanabe F, Katsura H, Takenaka S, et al. Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets. J Agric Food Chem. 1999;47(11):4736-41. doi:10.1021/jf990541b
15. Axe J. 10 Signs You Have a B Vitamins Deficiency (How to Boost B Vitamins Naturally). The Dr. Josh Axe Show. 2024 (Dr. Axe speaking; YouTube at 16:39-16:55: https://www.youtube.com/watch?v=PpssCzYFqDY).
16. Masten Rutar J, Jagodic Hudobivnik M, Nečemer M, et al. Nutritional Quality and Safety of the Spirulina Dietary Supplements Sold on the Slovenian Market. Foods. 2022;11(6):849. doi:10.3390/foods11060849
17. Misbahuddin M, Islam AZ, Khandker S, et al. Efficacy of spirulina extract plus zinc in patients of chronic arsenic poisoning: a randomized placebo-controlled study. Clin Toxicol (Phila). 2006;44(2):135-41. doi:10.1080/15563650500514400
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19. Karizi SR, Armanmehr F, Azadi HG, et al. A randomized, double-blind placebo-controlled add-on trial to assess the efficacy, safety, and anti-atherogenic effect of spirulina platensis in patients with inadequately controlled type 2 diabetes mellitus. Phytother Res. 2023;37(4):1435-1448. doi:10.1002/ptr.7674
20. Hariri M, Azizi-Soleiman F, Baradaran HR, et al. Spirulina Supplementation Can Reduce Serum Levels of C-Reactive Protein: A Systematic Review and Meta-Analysis on Randomized Clinical Trials. Int J Vitam Nutr Res. 2026;96(1):44330. doi:10.31083/IJVNR44330
21. Karimi S, Shaygannejad V, Mohammadalipour A, et al. Effects of spirulina (Arthrospira) platensis supplementation on inflammation, physical and mental quality of life, and anthropometric measures in patients with relapsing-remitting multiple sclerosis (RRMS): a triple-blinded, randomized, placebo-controlled trial. Nutr J. 2025;24(1):132. doi:10.1186/s12937-025-01200-x
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23. Mao TK, Van de Water J, Gershwin ME. Effects of a Spirulina-based dietary supplement on cytokine production from allergic rhinitis patients. J Med Food. 2005;8(1):27-30. doi:10.1089/jmf.2005.8.27
24. Moradi S, Foshati S, Poorbaferani F, et al. The effects of spirulina supplementation on serum iron and ferritin, anemia parameters, and fecal occult blood in adults with ulcerative colitis: A randomized, double-blinded, placebo-controlled trial. Clin Nutr ESPEN. 2023;57:755-763. doi:10.1016/j.clnesp.2023.08.019
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28. Chaouachi M, Gautier S, Carnot Y, et al. Spirulina supplementation prevents exercise-induced lipid peroxidation, inflammation and skeletal muscle damage in elite rugby players. J Hum Nutr Diet. 2022;35(6):1151-1163. doi:10.1111/jhn.13014
29. Pappas A, Tsiokanos A, Fatouros IG, et al. The Effects of Spirulina Supplementation on Redox Status and Performance Following a Muscle Damaging Protocol. Int J Mol Sci. 2021;22(7):3559. doi:10.3390/ijms22073559
30. Mathew B, Sankaranarayanan R, Nair PP, et al. Evaluation of chemoprevention of oral cancer with Spirulina fusiformis. Nutr Cancer. 1995;24(2):197-202. doi:10.1080/01635589509514407
31. Papakonstantinou E, Lympaki F, Savvidou A, et al. Impact of spirulina-enriched yogurt-like dessert on blood pressure in overweight individuals with high cardiometabolic risk: results from in vitro studies and a randomized, placebo-controlled clinical trial. Nutr Metab Cardiovasc Dis. 2026:104824. doi:10.1016/j.numecd.2026.104824
32. Martínez-Sámano J, Torres-Montes de Oca A, Luqueño-Bocardo OI, et al. Spirulina maxima Decreases Endothelial Damage and Oxidative Stress Indicators in Patients with Systemic Arterial Hypertension: Results from Exploratory Controlled Clinical Trial. Mar Drugs. 2018;16(12):496. doi:10.3390/md16120496
33. Hirahashi T, Matsumoto M, Hazeki K, et al. Activation of the human innate immune system by Spirulina: augmentation of interferon production and NK cytotoxicity by oral administration of hot water extract of Spirulina platensis. Int Immunopharmacol. 2002;2(4):423-34. doi:10.1016/s1567-5769(01)00166-7
34. Moradi S, Ziaei R, Foshati S, et al. Effects of Spirulina supplementation on obesity: A systematic review and meta-analysis of randomized clinical trials. Complement Ther Med. 2019;47:102211. doi:10.1016/j.ctim.2019.102211
35. Zeinalian R, Farhangi MA, Shariat A, et al. The effects of Spirulina Platensis on anthropometric indices, appetite, lipid profile and serum vascular endothelial growth factor (VEGF) in obese individuals: a randomized double blinded placebo controlled trial. BMC Complement Altern Med. 2017;17(1):225. doi:10.1186/s12906-017-1670-y
36. Yousefi R, Mottaghi A, Saidpour A. Spirulina platensis effectively ameliorates anthropometric measurements and obesity-related metabolic disorders in obese or overweight healthy individuals: A randomized controlled trial. Complement Ther Med. 2018;40:106-112. doi:10.1016/j.ctim.2018.08.003
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38. Miczke A, Szulińska M, Hansdorfer-Korzon R, et al. Effects of spirulina consumption on body weight, blood pressure, and endothelial function in overweight hypertensive Caucasians: a double-blind, placebo-controlled, randomized trial. Eur Rev Med Pharmacol Sci. 2016;20(1):150-6.
39. Ghaem Far Z, Babajafari S, Kojuri J, et al. Antihypertensive and antihyperlipemic of spirulina (Arthrospira platensis) sauce on patients with hypertension: A randomized triple-blind placebo-controlled clinical trial. Phytother Res. 2021;35(11):6181-6190. doi:10.1002/ptr.7254
40. Hamedifard Z, Milajerdi A, Reiner Ž, et al. 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 trials. Phytother Res. 2019;33(10):2609-2621. doi:10.1002/ptr.6441
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54. Machowiec P, Ręka G, Maksymowicz M, et al. Effect of Spirulina Supplementation on Systolic and Diastolic Blood Pressure: Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2021;13(9):3054. doi:10.3390/nu13093054
55. Park HJ, Lee YJ, Ryu HK, et al. A randomized double-blind, placebo-controlled study to establish the effects of spirulina in elderly Koreans. Ann Nutr Metab. 2008;52(4):322-8. doi:10.1159/000151486
56. Axe J. 11 Supplements Every 40+ Adult Should Consider. The Dr. Josh Axe Show. 2026 (Dr. Axe speaking, item 11: he recommends a superfood powder as another insurance policy, since many people are not getting enough berries and vegetables).
57. Hsiao G, Chou PH, Shen MY, et al. C-phycocyanin, a very potent and novel platelet aggregation inhibitor from Spirulina platensis. J Agric Food Chem. 2005;53(20):7734-40. doi:10.1021/jf051352y
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Dr. Josh Axe, DC, DNM, CNS

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Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

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