Written by the Plenthera team (trained in orthomolecular nutrition). Scientifically reviewed in April 2026. Last updated: 18 September 2026.
Spirulina is one of the oldest life forms on earth — a cyanobacterium that has been obtaining energy from sunlight through photosynthesis for billions of years. The Aztecs harvested it around Lake Texcoco; today spirulina is cultivated worldwide in alkaline freshwater ponds. What makes it special: a protein content of 55-70% (one of the highest in a natural food), combined with phycocyanin, iron, beta-carotene and B vitamins. At Plenthera you will find spirulina as organic raw chlorella-spirulina tablets from Big Food — with traceable origin and tested per batch for microcystins and heavy metals.
Spirulina vs Chlorella — which suits you?
| Aspect | Spirulina | Chlorella |
|---|---|---|
| Type | Cyanobacterium | True green alga |
| Protein content | 55-70% | 50-60% |
| Main pigment | Phycocyanin (blue) | Chlorophyll (green) |
| Cell wall | Soft — directly digestible | Hard — must be broken |
| B vitamins | High (but pseudo-B12) | Present (active B12 in variable amounts) |
| Profile | Protein, iron, phycocyanin | Chlorophyll, researched for binding heavy metals |
What is spirulina?
Spirulina (Arthrospira platensis) is a cyanobacterium — often called a "blue-green alga", although strictly speaking it is not an alga but a photosynthetic bacterium. It is a protein-rich superfood with phycocyanin, iron and B vitamins.
Under the microscope, spirulina looks like a spiral-shaped thread — hence the name. In nature it floats in alkaline freshwater lakes in tropical and subtropical areas, such as Lake Texcoco in Mexico (where the Aztecs harvested and traded it as "tecuitlatl") and Lake Chad in central Africa (where local communities still use it as "dihé"). For commercial production, spirulina is cultivated in controlled ponds with alkaline water — Hawaii, India, Taiwan and China are the dominant production hubs.
What sets spirulina apart nutritionally is the combination of properties: 55-70% protein (complete amino acid profile), 10-20% phycocyanin (a blue pigment protein being researched for its antioxidant properties), beta-carotene, vitamin K, gamma-linolenic acid (GLA), bioavailable iron and magnesium. A 5-gram serving provides approximately 3 grams of protein and a touch of almost all micronutrients — hence its position as a "superfood".
One important caveat: spirulina contains pseudo-B12 (corrinoids), which the human body does not recognise as active B12. Vegans and vegetarians who supplement B12 should use a specific methylcobalamin supplement for this — do not rely on spirulina.
What does science say about spirulina?
Spirulina is one of the most researched microalgae — thousands of publications exist on its composition and bioactive components. Much research focuses on phycocyanin: the blue pigment protein that gives spirulina its characteristic colour and is being researched in laboratory and animal models for antioxidant and immunomodulatory activity. Human studies are fewer in number and smaller in size (Karkos et al., 2011).
Authorised EU claims do exist for components in spirulina, provided the product meets the threshold: iron contributes to the reduction of tiredness and fatigue and to the normal function of the immune system; protein contributes to a growth in muscle mass (for products where at least 12% of the energy comes from protein). For spirulina as a whole, we describe only the composition and the lines of research.
Spirulina is a food supplement, not a medicine. If you take medication (especially immunosuppressants and blood thinners): consult a doctor or pharmacist beforehand.
Quality and purity — what to look out for
Spirulina is sensitive to cultivation conditions. Uncontrolled wild lakes can contain other cyanobacteria that produce microcystins — toxins that are harmful to the liver and nervous system. High-quality spirulina comes from controlled ponds where these toxins are tested for regularly.
Microcystin test: proves that the product is free of cyanotoxins. Laboratory report available.
Heavy metals: spirulina can accumulate heavy metals from polluted water. A test for lead, mercury, cadmium and arsenic (limits in Regulation (EU) 2023/915) is essential.
Organic certification: guarantees cultivation without pesticides or synthetic fertilisers.
Traceable origin: Hawaiian, Taiwanese and Indian production are known for stricter quality control.
At Plenthera we work exclusively with spirulina of verified origin, with laboratory reports available on request.
The forms of spirulina at Plenthera
Chlorella-Spirulina tablets Raw & Bio — Big Food (500 g / 1000 tablets, also 2+1 and 3+1)
Both microalgae combined in pressed tablets without binders or fillers — spirulina for protein, iron and phycocyanin, chlorella for chlorophyll and its cell wall properties. Practical on the go and for those who find the taste of powder strong. Also see the Chlorella + Spirulina Combi category.
Other forms on the market
Loose spirulina powder (deep blue-green, with the typical sea aroma, for smoothies and juices) and pure spirulina tablets are common forms. These are not currently in our range.
How do you use spirulina?
A simple basic approach to spirulina:
- Determine your dosage: daily supplementation (3-5 g), sports use (5-10 g) or microdose (1-2 g). With the 500 mg Big Food tablets, that is 6-10 tablets per day.
- Start with a low dosage (1-2 g) and build up gradually to let your digestion get used to it.
- If you use powder: mix it into a smoothie or juice with a strong flavour (mango, pineapple) — this softens the sea aroma.
- It can be taken with or without a meal; with a sensitive stomach, preferably with a meal.
- For B12 supplementation: do not use spirulina as your only source — choose a methylcobalamin supplement.
- If you take medication (immunosuppressants, blood thinners): consult beforehand.
Myths and misconceptions about spirulina
Myth 1: "Spirulina is a good source of B12 for vegans."
Incorrect and dangerous to claim. Spirulina contains pseudo-B12 (corrinoids), which humans do not recognise as active B12. Vegans and vegetarians should use a specific methylcobalamin supplement.
Myth 2: "The more spirulina, the more protein and energy."
Spirulina is rich in protein in dry matter, but because of the low typical daily dose (3-5 g) it provides only 1.5-3.5 grams of protein per serving in absolute terms. Compare that with 20-30 grams of protein in a substantial meal. Spirulina is a supplement, not a primary source of protein.
Myth 3: "Spirulina detoxes heavy metals from the body."
Not scientifically demonstrated — and the opposite may be true if the spirulina itself is contaminated with heavy metals. The body has its own detoxification system (liver and kidneys); supplements do not replace it.
Myth 4: "All spirulina is equally safe."
Incorrect. Spirulina from uncontrolled sources may contain microcystins, heavy metals or other contaminants. Only choose spirulina with a laboratory-tested profile and organic certification.
Combining spirulina with other supplements
Spirulina is often combined with other supplements for a broader nutritional profile. Popular combinations:
- Chlorella: complementary microalga — together they provide a broader profile (and are already combined in our Big Food tablets).
- Vitamin B12 (methylcobalamin): because spirulina does not provide active B12, a separate B12 is essential for vegans.
- Vitamin C: vitamin C increases iron absorption.
- Vegan Protein: for those who want protein as the main category — spirulina as a micronutrient bonus.
- Maca: a classic superfood combination in smoothies.
- Acerola: a natural source of vitamin C, complementary to the iron in spirulina.
Frequently asked questions
What is spirulina?
Spirulina (Arthrospira platensis) is a cyanobacterium — often called a blue-green alga. Rich in protein (55-70%) with phycocyanin, iron and B vitamins.
How does spirulina work?
Spirulina provides protein, minerals and pigments such as phycocyanin. Research focuses on antioxidant and immunomodulatory activity; human data is limited.
How much spirulina per day?
3-5 grams as a general daily serving. For more intensive use, up to 10 grams per day, optionally split over two moments.
When should you take spirulina?
The timing is flexible. With a sensitive stomach: with a meal. Many users take spirulina in the morning.
What is the difference between spirulina and chlorella?
Spirulina is a cyanobacterium with a blue-green colour, a soft cell wall and a high protein content. Chlorella is a true green alga with a hard cell wall (must be broken) and a high chlorophyll content.
Is spirulina a good source of B12?
No. Spirulina contains pseudo-B12, which humans do not recognise as active B12. Vegans should use a methylcobalamin supplement.
Does spirulina help with detox?
Not scientifically demonstrated. What is called "detox" is the natural function of the liver and kidneys.
Does spirulina have side effects?
Generally well tolerated. Some people report mild stomach complaints or headaches at the start. If you take medication, consult beforehand.
Spirulina for vegans — protein?
Spirulina is rich in protein in dry matter, but because of the low daily dose (3-5 g) it provides little protein in absolute terms. A supplement, not a primary source.
How do I recognise quality spirulina?
Traceable origin, organic certification, a microcystin test and a test for heavy metals. Ask for laboratory reports.
Sources
- Karkos PD. et al., "Spirulina in clinical practice: evidence-based human applications", Evid Based Complement Alternat Med (2011).
- Watanabe F. et al., "Pseudovitamin B12 is the predominant cobamide of an algal health food, spirulina tablets", J Agric Food Chem (1999).
- Regulation (EU) 2023/915 — maximum levels for certain contaminants in food (lead, cadmium, mercury, arsenic).
- Regulation (EU) 432/2012 — authorised health claims (iron, protein, vitamin C).
Disclaimer: This text is for informational purposes only and does not replace medical advice. Spirulina is a food or food supplement, not a medicine. If in doubt or if you take medication, we recommend consulting a doctor or orthomolecular therapist first.