Spirulina and chlorella are different algae
Spirulina (Arthrospira platensis) is a spiral-shaped blue-green microalga, strictly a cyanobacterium. Chlorella (here Chlorella pyrenoidosa) is a green single-celled alga. Both are sold dried, pressed into tablets.
Algae products compared
| Product | Alga | Daily dose | Per day | Pack lasts |
|---|---|---|---|---|
| NOW Foods Organic Spirulina 500 mg, 100 or 200 tablets | spirulina, organic, whole plant | 6 tablets | 3 g | about 16 or 33 days |
| Swanson Spirulina 500 mg, 180 tablets | spirulina | 2 tablets 3 times a day, preferably on an empty stomach with water | 3 g | 30 days |
| OstroVit Chlorella VEGE, 1000 tablets (248 g) | chlorella (Chlorella pyrenoidosa) | 4 tablets twice a day | 1980 mg | 125 days |
A spirulina tablet here weighs 500 mg and a chlorella tablet about 250 mg, so eight chlorella tablets are less algae than six spirulina tablets. Compare grams per day and the price per day on each card.
What is in the dose
The NOW Foods label lists 2 g of protein in the 3 g daily dose. The other labels only state the amount of algae. Neither alga has a reference intake (NRV), so no percentages are shown.
Quality and safety
Algae take up what is in the water they grow in, so how they are cultivated matters. NOW Foods sells an organic product. All labels name the alga by its Latin name. Algae can also contain iodine, so if you have a thyroid condition, ask a doctor first.
Health claims
There are no EU-authorised health claims for spirulina or chlorella. Under Regulation (EC) No 1924/2006 only authorised wording may be used, so this category promises nothing about energy, immunity, detox or any other effect. If a seller does, it is not an approved EU claim. If you are looking for nutrients that do carry authorised statements, see multivitamins and minerals.
Check before you take it
NOW Foods: adults only, and talk to a doctor if you are pregnant, breastfeeding, ill or taking medicines. OstroVit: not for children, pregnant or breastfeeding women, not for anyone allergic to an ingredient, and the label lists possible traces of several allergens, including milk, soy, peanuts and eggs. The Swanson label says to keep the product out of reach of young children.
Questions
Spirulina or chlorella?
They are different algae and neither has an authorised health claim. Choose by the dose in grams, how many tablets you want to swallow and the price per day.
How do I take them?
NOW Foods: 6 tablets a day. Swanson: 2 tablets three times a day, preferably on an empty stomach with water. OstroVit: 4 tablets twice a day.
Why is the tablet count so different?
Tablet sizes differ. 180 spirulina tablets last 30 days, 1000 chlorella tablets last 125 days.
Is the chlorella vegan?
The product is named VEGE and the ingredients are chlorella powder with an anti-caking agent, but read the allergen note on the label.
Who should ask a doctor first?
Pregnant and breastfeeding women, people with a thyroid condition, and anyone taking medicines.
Sources
- Regulation (EC) No 1924/2006 (nutrition and health claims)
- Regulation (EU) No 432/2012 (permitted health claims)
- EFSA: Health claims
Content reviewed by Inese Kalniņa, dietitian.
2026-10-20