The health benefits of spirulina

What is spirulina powder, what are the nutritional benefits and potential side effects and is it safe for everyone? We take a look at this food supplement.

Two bowls with spirulina powder and tablets

What is spirulina and how is it usually consumed?

Spirulina is a blue-green algae that is usually consumed either in powder form or as a supplement.

What is the nutritional profile of spirulina?

Spirulina is known as a nutrient-dense food as it is packed full of vitamins, including vitamins A, C, E and B vitamins, as well as a whole host of minerals such as calcium, magnesium, zinc and selenium.

In particular, vitamin C and selenium are both antioxidants and help protect our cells and tissues from damage.

This algae is also an excellent vegan source of iron, providing 1.4mg per 5g teaspoon which is about 16% of the recommended daily allowance (RDA) for men over 18 years and women over 50 years, and 10% for RDA for women aged 19-49 years old.

Spirulina is also high in protein, with just 1 tsp (5g) providing almost 3g of protein per serving.

How well researched are the benefits and risks of spirulina?

Most of the studies that have been conducted to date have been either on animals or in small human trials, so more research is needed before any health claims relating to spirulina can be confirmed.

There has been some research into the benefits of spirulina and its positive effects on blood glucose levels. In 2017 a paper was published which demonstrated that spirulina decreased blood glucose levels in diabetic mice and the researchers suggested that this may be beneficial in the future to those with type 1 diabetes. This is further supported by another study in the Journal of Medicinal Food that found spirulina supplementation of 2g a day for 2 months on 25 individuals with type 2 diabetes helped control blood sugar levels and improved their lipid profile. However, more research is needed before we can say for sure that spirulina is helpful in managing conditions such as diabetes.

A 2010 study on rabbits found that spirulina had anti-atherogenic effects (reducing the build-up of plaque within arterial walls) even when fed a high cholesterol diet.

There is also some evidence that spirulina may help reduce anaemia, although more research is required. One study on 40 older people with a history of anaemia found that supplementing with spirulina helped improve the haemoglobin levels in red blood cells.

There have also been a few trials into spirulina supplementation in sport, and early evidence that it may help improve both muscle strength and exercise performance.

Spirulina contains a phytonutrient known as c-phycocyanin, which also gives it a deep green/blue colour. Research has suggested that this phytonutrient has potential benefits, including anti-inflammatory properties, oxidative stress protection and neuroprotective qualities.

However, as already stated, the research that has been conducted to date has either been on animals or in small human trials so more research is needed to know the true efficacy of this algae in the population at large.

Are there any side effects of spirulina?

Spirulina also contains salt. One 5g teaspoon contains 0.13g of sodium which counts towards 2% of the recommended daily allowance (RDA) for adults. If you know salt is an issue for you, or you have high blood pressure then always check with your GP before supplementing. Others who should check with their GP before taking spirulina include those taking prescription medication, pregnant or breastfeeding women and anyone younger than 18.

Those with the condition called phenylketonuria (PKU) should avoid spirulina completely as it contains an amino acid called phenylalanine which they cannot metabolise, as should anyone with an autoimmune condition such as rheumatoid arthritis, lupus or multiple sclerosis.

Always make sure you buy spirulina from reputable brands or sources, as there has been concern in the past that it can be contaminated with toxins from bacteria known as cynobacteria.

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This article was published on 19th February 2018.

Nicola Shubrook is a nutritional therapist and works with both private clients and the corporate sector. She is an accredited member of the British Association for Applied Nutrition and Nutritional Therapy (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at

All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

Comments, questions and tips

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Rachael Krokowska's picture
Rachael Krokowska
27th Feb, 2018
Spirulina is a Cyanobacteria. Cyanobacteria or more commonly known as blue-green algae are able to form large growths in ponds, lakes, and some in rivers. Cyanobacteria also produce a number of toxins, cyanotoxins, which when ingested can cause harm or even death to animals and humans. There is lots of literature on this. The Scottish government has produced guidance on Cyanobacterial risks to human and animal health. I for one would not be taking this.
James Nightingale's picture
James Nightingale
4th Jul, 2019
I for one will not be taking advise from Rachael Krokowska, Russian spy.
Gregory Guerra Bieberach's picture
Gregory Guerra ...
28th Jun, 2018
Spirulina is FDA recognized as safe, is one of the few (Arthrospira, Chlorella, Dunaliella) which in fact do no produce any toxin, its consume is well documented as ancient and traditional in africa, mexico and south america.
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