Microalgae as superfoods: chlorellaspirulinanutritional valuesprecautionsalgae oilhow to take

What exactly are microalgae?

Algae (plural of alga) is a broad term, covering various different types of organisms that don’t necessarily share a common ancestor. Microalgae – microscopic algae – such as chlorella are single-celled organisms. Seaweed is known as macroalgae.

Microalgae may be right at the bottom of the food chain, but they’re among the oldest organisms on the planet, considered the original producers of our atmosphere (1). Along with bacteria, they’re still crucial for all life on Earth today. While around 50,000 species have been identified, only around 100 have been cultivated, and it’s likely anywhere up to 800,000 types exist (2).

Microalgae use carbon dioxide as energy for photosynthesis, in turn producing around half the oxygen we breathe (3). So as to efficiently trap sunlight for growth, they’re very high in chlorophyll. As with green vegetables, this explains their vivid green colour and much of their amazing nutritional value.



Chlorella is a type of single-celled green algae. It gets its name from the Greek chloros (green), and the Latin suffix ella (small).

Chlorella first gained attention in the post-war baby boom of the 1940s, as a possible way to keep the growing population well-nourished. Much research was carried out, but it proved simpler to focus on crops such as soybeans, so chlorella never really took off as a mass food source.

Nowadays it’s mostly cultivated in Japan and Taiwan – as a supplement, rather than a large-scale food supply. NASA have done a lot of research on using it in space stations – as a food and oxygen source – and it has proven quite stable in zero-gravity conditions (4). Maybe this ancient organism is still ahead of its time, and will come into its own in future.

“Capable of reproducing itself four times every 24 hours, chlorella is the fastest growing plant on earth. It also contains more chlorophyll and nucleic acids (DNA and RNA) than any plant on earth…. So complete is this wonder-food that, when consuming nothing other than chlorella, human life can be sustained for an extended period.”
Plant-based triathlete Brendan Brazier, Thrive

Chlorella benefits

  • Very good as a detoxifier of environmental pollutants, e.g. heavy metals such as lead and cadmium (5, 6).
  • Very good at supporting the immune system (7).
  • Helps to reduce body fat, lower cholesterol and normalise blood glucose, so may be useful against diabetes (8).
  • May help fight cancer (9).
  • May give particular support to those receiving chemotherapy (10).
  • May help protect the health of those receiving radiotherapy (11).



Spirulina is actually not a type of algae, but a special kind of bacteria. Cyanobacteria behave in a very similar way to microalgae, as they create energy through photosynthesis, and produce oxygen, so are commonly known as blue-green algae.

Unlike chlorella, spirulina has more than one cell, and often grows in a spiral shape, hence the name.

Freshwater blue-green algae was first cultivated and traded as food in Mexico by the Aztecs, as well as being a food source in Central Africa. In the present day, Hawaiian is often considered the purest and best nutritionally.

Spirulina benefits

  • Promotes healthy gut flora, by enhancing growth of lactic acid bacteria (probiotics). It’s especially useful against candida (12).
  • Very good at detoxifying the body from pollutants such as heavy metals (13), especially arsenic (14)
  • Very good for supporting the immune system and fighting infection (15).
  • Helps to lower cholesterol (16) and prevent high blood pressure (17).
  • Helps normalise blood glucose levels, so could be helpful for diabetes (18).
  • Can be beneficial for anaemia (19).
  • Potentially helpful against cancer (20).
  • May help neurological function, specifically in those with Parkinson’s (21) or memory dysfunction (22).

Nutritional values of spirulina and chlorella

These vary a great deal, depending on how and where the product is grown, the ways in which it’s processed, and even weather conditions.

The following table gives an overview of likely values, so as to compare them side by side, but check the packaging for variations when choosing a product. The table shows values per 100g, but this is obviously much more than a daily amount. A serving is usually around 3-5g.

As you’ll see, spirulina and chlorella share many strengths in common, such as their high protein content. In fact they’re both considered ‘complete’ proteins, providing all essential amino acids (all 19 amino acids in the case of chlorella).

They’re both notably high in B vitamins and a range of minerals. Chlorella is especially high in vitamin A, iron and zinc.

Although complete figures are not available from this source for vitamin K, both do have high levels, due to their high levels of chlorophyll.

Spirulina & Chlorella Nutrients

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When to avoid spirulina and chlorella

Spirulina and chlorella should be avoided by those allergic to iodine.

As they’re high in vitamin K – a blood coagulant – it’s advisable not to take them if you’re on blood-thinning medication such as Warfarin.

Those with the rare condition phenylketonuria should avoid taking spirulina.

For use in pregnancy or for children, it’s best to take advice from a practitioner, as some say they’re both best avoided.

Some believe you should avoid spirulina and chlorella if you have an auto-immune condition, or are taking immune suppressant medication, as they stimulate the immune system. Others say that’s not necessarily the case, or that it can even be beneficial, so more research is needed. You may want to seek further advice from a practitioner in this case.


Marine algae oil

Algae oil is best known for its omega 3 value – a notoriously difficult nutrient to get from a vegan diet.

The omega 3 found in chia and flax, for example, is alpha-linolenic acid (LNA), which is harder for the body to process than the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) most commonly found in animal products (24). As a plant-based alternative to fish and krill oil, marine algae oil is high in DHA and EPA. Fish don’t actually produce omega 3 anyway – the original source is marine algae, which is then ingested by fish.

We use Testa capsules. At the time of writing there are no certified organic options. We asked Testa about that, and this was their response:

“Algae oil is not produced in an agricultural environment and the principles of organic agriculture therefore do not apply here. However, the algae oil is produced under very controlled conditions, making our oil very pure and fresh compared to fish- or krill oil.”

How to take microalgae

Powder is a great form of spirulina or chlorella to use in smoothies or juices, or just in water. It’s also available in the more convenient tablet form, but this can be a more expensive way to take any significant amount.

If you can spread your intake throughout the day, or just a couple of times a day, you will gain the most nutritional value.

When buying spirulina or microalgae, make sure it’s from a pure and reliable source, as contaminated sources can cause a wide range of health problems.

When buying chlorella, make sure the packet says the cell wall has been broken or cracked in processing. Chlorella can’t otherwise be digested, as we don’t have the necessary enzymes in our bodies. Good quality products will have this as standard.

Recommended serving sizes will vary, so check the packaging, or ask a practitioner what would work best for you.

Algae oil is usually taken in capsule form, but is also available as a liquid. Again, it’s best to spread your intake out if possible.

Got any tips or questions of your own about spirulina, chlorella and other microalgae superfoods? Leave us a comment below, we’d love to hear from you.


Health benefits of seaweed »
Vitamin B: benefits & plant-based sources »


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