Spirulina powder contains about 57.5 g of protein per 100 g, according to USDA FoodData Central, more than any dal, paneer or egg by weight. But spirulina is eaten by the teaspoon, so a realistic 5 g serving gives only about 2.9 g of protein.
- The 57.5 g is crude protein (nitrogen × 6.25). Microalgae contain some non-protein nitrogen, so true protein is probably a little lower.
- Its amino acid profile meets the WHO adult reference pattern for every essential amino acid, with lysine the lowest at about 117%.
- Spirulina is rich in iron (28.5 mg per 100 g) but is not a reliable vitamin B12 source.
Updated 27 October 2026 · Data: USDA FoodData Central, IFCT 2017 (ICMR-NIN), ICMR-NIN Nutrient Requirements 2020, WHO/FAO/UNU 2007
In this article
- Spirulina nutrition per 100 g
- Spirulina protein per teaspoon and per portion
- Is spirulina protein really 57 g per 100 g?
- Is spirulina a complete protein?
- Spirulina protein vs dal, paneer, egg and moringa
- Iron and vitamin B12: what spirulina does and does not give you
- Safety and quality: what to check
- How to use spirulina in an Indian kitchen
- Frequently asked questions
Spirulina protein per 100 g is the number that sells spirulina: "60% protein", "more protein than meat", "a complete protein". Some of that is true and some of it needs context. This guide takes the figures from one consistent source, USDA FoodData Central, compares them with Indian foods from the Indian Food Composition Tables 2017 (IFCT) published by ICMR's National Institute of Nutrition, and then asks the practical question: how much protein does the spoonful you actually eat deliver? [1][2]
Spirulina is the dried biomass of Arthrospira platensis (and the related A. maxima), a spiral-shaped cyanobacterium often called blue-green algae. It has no traditional name in Indian languages; it is sold as "spirulina" across the country, as a powder, tablets or capsules. IFCT 2017 does not include it, which is why this post relies on USDA data for spirulina itself [2].
Spirulina nutrition per 100 g
USDA's entry for dried spirulina is the most widely used reference analysis. Here are the headline values.
| Nutrient | Per 100 g |
|---|---|
| Energy | 290 kcal (1,210 kJ) |
| Protein | 57.5 g |
| Carbohydrate (by difference) | 23.9 g |
| Total dietary fibre | 3.6 g |
| Total fat | 7.7 g |
| Iron | 28.5 mg |
| Calcium | 120 mg |
| Magnesium | 195 mg |
| Potassium | 1,360 mg |
| Sodium | 1,050 mg |
| Copper | 6.1 mg |
| Riboflavin (B2) | 3.67 mg |
| Thiamin (B1) | 2.38 mg |
| β-carotene | 342 µg |
| Vitamin B12 | 0 µg (see below) |
| Moisture | 4.7 g |
Source: USDA FoodData Central, SR Legacy, "Seaweed, spirulina, dried", FDC ID 170495 (NDB 11667); protein calculated as nitrogen × 6.25 [1]. Values for any one brand will differ with strain, growing conditions and drying.
Two things stand out. Spirulina is over half protein by weight and very low in moisture, which is why it beats every Indian staple per 100 g. And it is unusually rich in iron, copper and B vitamins for a plant-like food. It is also fairly salty for a powder, at about 1 g sodium per 100 g, though in teaspoon amounts that adds only around 50 mg.
Spirulina protein per teaspoon and per portion
Spirulina is light, strongly flavoured and usually taken a teaspoon at a time. USDA weighs a tablespoon at 7 g, so a level teaspoon is roughly 2–3 g; a heaped one can be closer to 5 g. Weigh your own spoon once if you want accuracy.
| Amount | Roughly equals | Protein | Iron | Man, 65 kg (54 g/day) | Woman, 55 kg (46 g/day) |
|---|---|---|---|---|---|
| 3 g | 1 level teaspoon | 1.7 g | 0.9 mg | 3% | 4% |
| 5 g | 1 heaped teaspoon | 2.9 g | 1.4 mg | 5% | 6% |
| 7 g | 1 level tablespoon | 4.0 g | 2.0 mg | 7% | 9% |
| 10 g | about 1½ tablespoons | 5.8 g | 2.9 mg | 11% | 13% |
Calculated by Bhāvi from USDA values (57.5 g protein, 28.5 mg iron per 100 g) [1]. RDA: 0.83 g protein per kg body weight per day, ICMR-NIN 2020 [3]. Percentages rounded.
The honest reading: spirulina is a protein-dense food eaten in tiny amounts. A daily spoonful adds a few grams of protein, useful but not a replacement for dal, milk, curd, eggs or pulses, which supply 6–10 g in a single serving.
Is spirulina protein really 57 g per 100 g?
Almost every food composition table, including USDA's entry for spirulina, measures total nitrogen and multiplies it by 6.25 to estimate protein [1]. That factor assumes all the nitrogen sits in protein. In microalgae, some of it does not: it is in nucleic acids, pigments and free amino compounds.
A 2023 ETH Zurich study of eight commercial microalgae found that non-protein nitrogen made up 3.4–15.4% of total nitrogen, and that the average nitrogen-to-protein factor for microalgae was 5.3, not 6.25 [5]. That study did not test spirulina specifically, so the exact correction for spirulina is unknown. As a rough illustration only, applying 5.3 instead of 6.25 to USDA's figure would give about 49 g of true protein per 100 g (Bhāvi's estimate). Either way, spirulina remains far more protein-dense than any dal; the point is simply that "57%" is an upper-end figure.
Is spirulina a complete protein?
Protein quality depends on whether a food supplies each essential amino acid in the proportions humans need. The WHO/FAO/UNU expert consultation published an adult reference pattern in milligrams per gram of protein [4]. Comparing USDA's amino acid values for spirulina with that pattern gives the scores below.
| Essential amino acid | Spirulina (mg/g protein) | Adult reference (mg/g protein) | Score |
|---|---|---|---|
| Histidine | 18.8 | 15 | 125% |
| Isoleucine | 55.8 | 30 | 186% |
| Leucine | 86.1 | 59 | 146% |
| Lysine | 52.5 | 45 | 117% |
| Methionine + cysteine | 31.5 | 22 | 143% |
| Phenylalanine + tyrosine | 93.2 | 30 | 311% |
| Threonine | 51.7 | 23 | 225% |
| Tryptophan | 16.2 | 6 | 269% |
| Valine | 61.0 | 39 | 157% |
Spirulina: USDA FDC 170495 amino acid values divided by 57.5 g protein [1]. Reference: WHO Technical Report Series 935, Table 49 [4]. Scores calculated by Bhāvi; they do not account for digestibility.
Every essential amino acid clears the reference, and lysine, the amino acid most cereals are short of, is the lowest at about 117%. So on paper spirulina protein is complete. Two caveats: these scores are calculated against crude protein, and they ignore digestibility, which has not been well measured in people for whole spirulina powder. In practice, because the amount eaten is small, spirulina's amino acid balance matters far less than the dals and grains on the same plate.
Spirulina protein vs dal, paneer, egg and moringa
Per 100 g, spirulina leads every Indian protein food. Per serving, it falls to the bottom, because nobody eats spirulina in the quantities they eat dal or paneer.
| Food | Protein per 100 g | Typical serving | Protein per serving |
|---|---|---|---|
| Spirulina powder | 57.5 g | 5 g | 2.9 g |
| Soybean, brown | 35.6 g | 30 g | 10.7 g |
| Moong dal (green gram, split) | 23.9 g | 30 g (raw, for 1 bowl) | 7.2 g |
| Chicken breast, skinless | 21.8 g | 100 g | 21.8 g |
| Besan (chana dal) | 21.6 g | 30 g (1 chilla) | 6.5 g |
| Paneer | 18.9 g | 50 g | 9.4 g |
| Egg, whole | 13.3 g | 1 egg (about 50 g) | 6.6 g |
| Cow milk, whole | 3.3 g | 200 g (1 glass) | 6.5 g |
| Moringa leaf powder | about 25–30 g | 5 g | 1.2–1.5 g |
Spirulina: USDA FDC 170495 [1]. Others: IFCT 2017 codes B024, B010, N003, B001, L003, M001 and L002, raw values [2]. Moringa: range from our moringa powder nutrition guide. Serving sizes are typical household amounts chosen by Bhāvi for illustration.
If protein is the goal, a bowl of dal or a besan chilla does more than any spoonful of powder. For more than 30 Indian foods side by side, see our full IFCT table of protein per 100 g in dals, millets and seeds.
Iron and vitamin B12: what spirulina does and does not give you
Iron
At 28.5 mg per 100 g, spirulina is one of the most iron-dense foods in a typical pantry [1]. A 5 g serving supplies about 1.4 mg, roughly 7% of ICMR-NIN's RDA for men (19 mg a day) and 5% for women (29 mg a day) [3]. A 2025 systematic review of 32 studies on spirulina and chlorella (25 in animals, only 7 in humans) reported improvements in haemoglobin and ferritin, while noting that longer human trials are still needed [7]. That is early, mostly animal evidence. Spirulina is not a treatment for anaemia; if you suspect low iron, get tested and follow your doctor's advice.
Vitamin B12
Spirulina is often sold as a vegetarian B12 source. The evidence says otherwise. In a study of spirulina tablets, a common microbiological test overestimated B12 by six to nine times compared with a method that measures only the forms humans can use, and 83% of the B12-like compound that was purified turned out to be pseudovitamin B12, which is inactive in humans [6]. USDA lists spirulina's vitamin B12 as zero [1]. Vegetarians and vegans should rely on dairy, fortified foods or a supplement advised by a doctor instead.
Safety and quality: what to check
In 2011, the United States Pharmacopeia's expert committee reviewed human trials, animal studies and 31 adverse event reports and gave Spirulina platensis and S. maxima a Class A safety rating [8]. The bigger risk is contamination, not spirulina itself.
- Microcystins. These liver toxins are made by other cyanobacteria that can grow alongside algae in open water. A US study of 18 algal dietary supplements found some contained more than 40 times a proposed maximum of 1 µg/g [9], and a Belgian survey found microcystins in 9 of 35 algal supplements, three above that level, traced to Microcystis [10]. These studies covered algal supplements in general, not only spirulina.
- Heavy metals and other contaminants. Reviewers have called for closer monitoring of cyanotoxins, heavy metals, pesticides and polycyclic aromatic hydrocarbons in spirulina products, because people take them in gram amounts every day [11][12].
- Phenylalanine. Spirulina contains about 2.8 g phenylalanine per 100 g [1], so people with phenylketonuria (PKU) should avoid it unless their doctor says otherwise.
Practical checks: buy from a seller who can share batch test results for microcystins and heavy metals, choose cultivated rather than wild-harvested algae, and start with half a teaspoon a day. If you are pregnant, breastfeeding, have a medical condition or take regular medication, ask your doctor first.
How to use spirulina in an Indian kitchen
Spirulina tastes strongly of the sea, so it works best where other flavours can carry it.
- Nimbu pani: ½ teaspoon in cold water with lemon, a little jaggery and a pinch of black salt. The vitamin C from lemon may also help iron absorption.
- Smoothies and lassi: blend 1 teaspoon with banana, mango or curd.
- Chutney podi or laddoos: stir a teaspoon into a batch of dry chutney powder or date-and-nut laddoos.
- Add it after cooking: heat dulls the colour, so stir it into dal, raita or batter just before serving rather than boiling it.
Store spirulina airtight, away from light, heat and moisture, and use a dry spoon.
From the Dhatu pantry
- Organic Spirulina Powder: dried Arthrospira platensis, single ingredient
- Organic Moringa Powder (Drumstick Leaf Powder): a calcium and β-carotene booster for dal and chutney podi
- Organic Besan: about 21.6 g protein per 100 g, eaten in far bigger portions
- Read next: Moringa powder nutrition and protein per 100 g
- Read next: Protein per 100 g in Indian dals, millets and seeds
- Read next: Besan protein per 100 g, with portion sizes
Frequently asked questions
How much protein is in 100 g of spirulina?
About 57.5 g per 100 g of dried spirulina powder, according to USDA FoodData Central. This is a crude protein figure (nitrogen × 6.25), so the true protein content is probably somewhat lower.
How much protein is in 1 teaspoon of spirulina?
A level teaspoon of spirulina powder weighs about 2–3 g and gives roughly 1.2–1.7 g of protein. Even 10 g, about one and a half tablespoons, gives under 6 g.
Is spirulina a complete protein?
On paper, yes. Its amino acid profile meets every essential amino acid in the WHO/FAO/UNU 2007 adult pattern, with lysine the lowest at about 117% of the reference. Digestibility and the small amounts people eat limit how much it adds in practice.
Does spirulina have more protein than eggs or chicken?
Per 100 g, yes: 57.5 g against 13.3 g for whole egg and 21.8 g for chicken breast. Per serving, no: 5 g of spirulina gives 2.9 g of protein, while one egg gives about 6.6 g.
Is spirulina a good source of vitamin B12?
No. Research on spirulina tablets found that most of the B12-like compound is pseudovitamin B12, which humans cannot use, and USDA lists spirulina's vitamin B12 as zero. Vegetarians and vegans need another reliable B12 source.
How much iron is in spirulina?
USDA lists 28.5 mg of iron per 100 g, so 5 g gives about 1.4 mg. That is roughly 7% of ICMR-NIN's daily iron RDA for men (19 mg) and 5% for women (29 mg).
Is spirulina safe to eat every day?
The US Pharmacopeia gave Spirulina platensis and Spirulina maxima a Class A safety rating in 2011, but product quality varies and some algal supplements tested abroad contained microcystin toxins. Choose tested products, start small, and check with a doctor if you are pregnant, have PKU or take medication.
Spirulina is sold widely in India, yet the country's own food composition tables have no entry for it, and many labels quote USDA's reference analysis, parts of which date back to the 1980s. Three gaps deserve attention. First, published analyses of spirulina grown in India, reporting true protein with a species-specific nitrogen factor rather than the default 6.25. Second, human studies of how well whole spirulina protein and iron are digested and absorbed in real meals. Third, routine, public testing for microcystins and heavy metals, with clear Indian limits for algal foods. Until then, readers can ask sellers for batch test reports, and treat "60% protein" as a per-100 g fact, not a per-spoon promise.
This article is for general information and is not medical or dietary advice. Spirulina is a food, not a treatment for any disease. If you are pregnant, have a medical condition such as PKU, or take regular medication, speak to a doctor or registered dietitian.
References
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy: Seaweed, spirulina, dried (FDC ID 170495). fdc.nal.usda.gov
- Longvah T, Ananthan R, Bhaskarachary K, Venkaiah K. Indian Food Composition Tables 2017. National Institute of Nutrition (ICMR), Hyderabad. nin.res.in (PDF)
- ICMR-National Institute of Nutrition. A Brief Note on Nutrient Requirements for Indians, the Recommended Dietary Allowances (RDA) and the Estimated Average Requirements (EAR), 2020. nin.res.in (PDF)
- WHO/FAO/UNU. Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935. Geneva: World Health Organization; 2007. iris.who.int
- Sägesser C, Kallfelz JM, Boulos S, Hammer L, Böcker L, Portmann R, Nyström L, Mathys A. A novel approach for the protein determination in food-relevant microalgae. Bioresour Technol. 2023;390:129849. PubMed 37813318 · doi:10.1016/j.biortech.2023.129849
- Watanabe F, Katsura H, Takenaka S, Fujita T, Abe K, Tamura Y, Nakatsuka T, Nakano Y. Pseudovitamin B12 is the predominant cobamide of an algal health food, spirulina tablets. J Agric Food Chem. 1999;47(11):4736-41. PubMed 10552882 · doi:10.1021/jf990541b
- Lacurezeanu A, Vodnar DC. Arthrospira platensis and Chlorella vulgaris consumption on iron status: a systematic review of in vivo studies. Mol Nutr Food Res. 2025;69(24):e70318. PubMed 41255135 · doi:10.1002/mnfr.70318
- Marles RJ, Barrett ML, Barnes J, Chavez ML, Gardiner P, Ko R, et al. United States Pharmacopeia safety evaluation of spirulina. Crit Rev Food Sci Nutr. 2011;51(7):593-604. PubMed 21793723 · doi:10.1080/10408391003721719
- Miller TR, Xiong A, Deeds JR, Stutts WL, Samdal IA, Løvberg KE, Miles CO. Microcystin toxins at potentially hazardous levels in algal dietary supplements revealed by a combination of bioassay, immunoassay, and mass spectrometric methods. J Agric Food Chem. 2020;68(30):8016-25. PubMed 32597644 · doi:10.1021/acs.jafc.0c02024
- Van Hassel WHR, Ahn AC, Huybrechts B, Masquelier J, Wilmotte A, Andjelkovic M. LC-MS/MS validation and quantification of cyanotoxins in algal food supplements from the Belgium market and their molecular origins. Toxins (Basel). 2022;14(8):513. PubMed 36006175 · doi:10.3390/toxins14080513
- Grosshagauer S, Kraemer K, Somoza V. The true value of spirulina. J Agric Food Chem. 2020;68(14):4109-15. PubMed 32133854 · doi:10.1021/acs.jafc.9b08251
- Ibrahim MEE, Demirel S, Yıkmış S, Tokatlı Demirok N, Ahmed MBO, Amin AK. Spirulina as a sustainable functional ingredient: nutrient density, bioactives, and food applications. Front Nutr. 2026;13:1810841. PubMed 42063958 · doi:10.3389/fnut.2026.1810841
