Spirulina vs. Chlorella

How does Spirulina differ from Chlorella and other blue-green algae?

By: Markita Lewis, MS, RD

Algae are incredibly powerful superfoods that can benefit anyone who takes them as part of their daily health regimen.

When it comes to picking the best algae dietary supplement, many people have questions about the different types of algae that are available. They tend to ask, "How does spirulina differ from chlorella and other blue-green algae?"

Out of the available algae supplements available, spirulina and chlorella supplements are the most popular types. At first glance, they may seem similar, but spirulina and chlorella are two different varieties of microalgae that definitely have unique properties.

This article details the difference between spirulina and chlorella, cultivation and processing, the nutritional benefits of spirulina vs chlorella, and which may be best for you.

Physical Differences Between Spirulina and Chlorella

Before we get into the differences between spirulina and chlorella, it’s important to know what microalgae are.

Microalgae are microscopic, single-celled, or multi-celled algae that undergo photosynthesis and produce nutrients and oxygen to be used for a variety of purposes1. In addition to being used as a food supplement, microalgae are used in industries including biofuels, health products, and even cosmetics. 

Spirulina and chlorella are very similar in the fact that they are both types of microalgae, but they have notable physical differences.

Spirulina is a type of marine cyanobacteria. Unlike most normal bacteria, cyanobacteria contain chlorophyll-a and can produce oxygen during photosynthesis. Spirulina has a spiral shape, lacks a true nucleus, and appears to be blue-green thanks to an antioxidant pigment it contains called phycocyanin2.

In comparison, chlorella is a spherical-shaped, single-celled alga that has a true nucleus. Chlorella is a solid green-colored form of algae due to having both chlorophyll-a and chlorophyll-b pigments for photosynthesis.

The size difference between these microalgae is also significant - spirulina can sometimes be up to 100-times larger than chlorella.

Cultivation Differences Between Spirulina and Chlorella

When given the right conditions, microalgae can grow to great masses very quickly. Each type of microalgae has its ideal growing environment that influences how they are cultivated.

Spirulina tends to grow best in freshwater ponds, rivers, and lakes that have a relatively high alkaline content. A high pH environment also increases spirulina’s antioxidant activity3.

In order to produce exemplary crops, spirulina must be cultivated in environments with moderate temperatures and abundant sunshine. In most natural environments, the waters where spirulina flourishes are usually home to very few other organisms, so harvesting the crop is easier. Traditionally spirulina was harvested from Lake Texcoco in Mexico and the north-central African country of Chad. Today Nutrex Hawaii grows its spirulina on the Kona coast of Hawaii.

Chlorella vulgaris (the most common chlorella used in supplements) is also grown in fresh water and has similar requirements for temperature and sunlight. But, it can grow at slightly lower pH levels than spirulina. It tends to occupy waters with other organisms due to its microscopic size, making chlorella much more difficult to harvest and cultivate.

Processing Differences Between Spirulina and Chlorella

It is essential that microalgae supplements are in their most bioavailable form in order to get the most benefits for your health.

Chlorella is traditionally more difficult to process than spirulina, due to the fact that it has an indigestible cellulose wall. Before it can be made available for human consumption, it first has to undergo a complex process in order to mechanically break the cellulose wall.

If the cellulose wall isn't broken, then the body won't be able to digest it because we lack the enzymes to do so. This mechanical process is not only complex, but it requires expensive equipment to perform. As a result, the cost of chlorella supplements is ultimately significantly higher.

In comparison, spirulina has an easily digestible cellulose wall and is readily available for human consumption. Spirulina supplements can be immediately digested and absorbed when taken, so you don’t need a complex manufacturing process. This in turn reduces the cost of purchasing spirulina. 

Nutritional Differences Between Spirulina and Chlorella

Both spirulina and chlorella are classified as superfoods, so they are both among the richest nutrient sources on the planet. But when you look at the nutrient content of chlorella vs spirulina, there are some notable differences.

Spirulina has a higher percentage of protein compared to chlorella. Spirulina also contains vitamins and minerals including potassium, copper, calcium, iron, and vitamins K1, K2, B1, B3, B6, and B124.

In comparison, chlorella is higher in iron, magnesium, zinc, omega-3 fatty acids, and vitamins A, D, and B125. Both spirulina and chlorella contain all nine essential amino acids and share other nutrients.

Chlorella and spirulina have their own strengths when it comes to certain antioxidants. Spirulina has a higher percentage of beta-carotene and phycocyanin, while chlorella has a greater concentration of chlorophyll (as evidenced by its dark green color).

Additional Differences Between Spirulina, Chlorella, and Other Blue-Green Algae

Here are some other quick differences between spirulina, chlorella, and blue-green algae:

  • Spirulina is easier on the digestive system than chlorella and other types of blue-green algae
  • Spirulina offers the highest level of gamma-linolenic acid (GLA), a "good fat" that is vital for the health and function of the brain, heart, and other body organs and systems
  • Chlorella may cause skin photosensitivity, meaning that it can potentially increase your risk of getting sunburn and sun rash

Which Microalgae Should You Choose?

Both spirulina and chlorella each exhibit incredible health benefits when taken as part of a daily diet. However, due to a significantly higher level of certain beneficial nutrients, and a unique antioxidant profile, spirulina may be a superior choice to chlorella and other types of blue-green algae.

No matter which algae supplement you choose, choose brands that put consumer safety first. Microalgae can be easily contaminated by heavy metals and other harmful contaminants, so choose a brand that uses extensive testing for safe and pure products. 


  1. Camacho, F., Macedo, A., & Malcata, F. (2019). Potential Industrial Applications and Commercialization of Microalgae in the Functional Food and Feed Industries: A Short Review. Marine drugs, 17(6), 312. https://doi.org/10.3390/md17060312
  2. Romay, C., Armesto, J., Remirez, D., González, R., Ledon, N., & García, I. (1998). Antioxidant and anti-inflammatory properties of C-phycocyanin from blue-green algae. Inflammation research: official journal of the European Histamine Research Society ... [et al.], 47(1), 36–41. https://doi.org/10.1007/s000110050256
  3. Ismaiel, M. M., El-Ayouty, Y. M., & Piercey-Normore, M. (2016). Role of pH on antioxidants production by Spirulina (Arthrospira) platensis. Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology], 47(2), 298–304. https://doi.org/10.1016/j.bjm.2016.01.003
  4. Gutiérrez-Salmeán, G., Fabila-Castillo, L., & Chamorro-Cevallos, G. (2015). NUTRITIONAL AND TOXICOLOGICAL ASPECTS OF SPIRULINA (ARTHROSPIRA). Nutricion hospitalaria, 32(1), 34–40. https://doi.org/10.3305/nh.2015.32.1.9001
  5. Bito, T., Okumura, E., Fujishima, M., & Watanabe, F. (2020). Potential of Chlorella as a Dietary Supplement to Promote Human Health. Nutrients, 12(9), 2524. https://doi.org/10.3390/nu12092524