spirulina powder and capsules

Spirulina: benefits, dosage, side effects

Find out all about spirulina, including what it does, the benefits to taking it and how much you might need

Written by Jack Feeney on January 21, 2019 Reviewed by Amanda Hamilton on January 30, 2019


What is spirulina and what does it do?

Spirulina is a type of blue-green algae that grows in freshwater ponds and lakes.1 It’s packed with nutrients, including B vitamins, beta-carotene, copper and iron, as well small amounts of magnesium, potassium and manganese.2

Spirulina is a vegan source of vitamin B12 – a vitamin some vegans and vegetarians may be lacking, as it’s mainly found in meat.3,4 It became popular after it was discovered that NASA gave it to astronauts on space missions as a food supplement.5

Research shows that spirulina could be helpful for lowering ‘bad’ cholesterol and high blood pressure. It may have anti-inflammatory properties, too.6,7,8

You can take spirulina in tablets, capsules or as a powder that can be added to shakes and smoothies for a nutritional boost. It’s also increasingly popular as an ingredient in snack, or energy, balls.

Benefits of spirulina

What does spirulina do in the body?

There’s a growing amount of research9 into the potential health benefits of spirulina:

1. It could help lower ‘bad’ cholesterol

High cholesterol is a significant risk factor for heart disease – a major cause of death in the UK. But spirulina has shown some promise at reducing levels of LDL, or ‘bad’, cholesterol.

In a 2018 meta-analysis of research, Chinese scientists reported that spirulina supplements had a ‘favourable effect’ on improving LDL cholesterol and triglyceride levels (a type of fat in the blood).10 Spirulina was also found to help reduce blood glucose levels – another risk factor for heart disease – which lead the team to conclude that spirulina could be considered in the ‘prevention and treatment of cardiovascular disease in humans’.11

2. It might reduce high blood pressure too

Likewise, spirulina could help lower blood pressure in people with type 2 diabetes.

A 2008 study published in Nutrition Research and Practice found people with type 2 diabetes who took the blue-green algae every day for 12 weeks experienced a reduction in blood pressure. It seemed to be more effective if the patient’s triglyceride levels were high, too.12 Similar results were recorded by a 2016 trial of 40 overweight people who had high blood pressure. Volunteers who took spirulina for three months saw improvements in their blood pressure, body weight and BMI, while those taking a placebo saw no significant changes.13

3. Potential antioxidant and anti-inflammatory properties

Spirulina is known to contain antioxidants, which help prevent our cells from damage caused by free radicals.14 This damage can cause long-term inflammation which may lead to conditions such as heart disease and high blood pressure,15 among others including dementia. Phycocyanin is one of the major antioxidant compounds in spirulina.16 It’s believed to fight free radicals and help prevent inflammation in the body.17,18


How much spirulina is safe to take?

While there’s no official recommended daily dosage for spirulina, studies have found that between 1-8g a day could be effective.19

Make sure you follow any instructions or recommendations on the product label before taking. Talk to your GP or a trained dietician or nutritionist if you’re concerned.

You should not take spirulina if you:20
  • are pregnant – there’s not enough evidence to prove it is safe
  • have an auto-immune disease – it may cause the condition to flare up
  • are taking blood-thinning medication – it may slow blood clotting

If you are on any medication, check with your doctor that it is safe to take spirulina at the same time.

Side effects

What are the side effects of taking spirulina?

In studies, there have been very few reported side effects associated with spirulina, but the most common include:21,22
  • insomnia
  • abdominal issues
  • vomiting
  • allergic reactions

Stop taking spirulina if you experience any of the above and seek medical advice.

Shop Superfood Supplements Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.


1. Encyclopedia.com. Spirulina

2. As above

3. Kamal Patel. examine.com. Spirulina 4. NHS. Vegetarian and vegan diets Q&A 5. Karkos PD, et al. Spirulina in Clinical Practice: Evidence-Based Human Applications 6. Huang H, et al. Quantifying the effects of spirulina supplementation on plasma lipid and glucose concentrations, body weight, and blood pressure 7. Lee E H, et al. A randomized study to establish the effects of spirulina in type 2 diabetes mellitus patients 8. Shih C M, et al. Anti-inflammatory and antihyperalgesic activity of C-phycocyanin

9. As Source 5
10. As Source 6
11. As Source 6
12. As Source 7

13. Miczke A, et al. Effects of spirulina consumption on body weight, blood pressure, and endothelial function in overweight hypertensive Caucasians: a double-blind, placebo-controlled, randomized trial 14. Wu Q, et al. The antioxidant, immunomodulatory, and anti-inflammatory activities of Spirulina: an overview

15. As above

16. Joe Leech. Healthline. 10 health benefits of Spirulina

17. As Source 8

18. Reddy M C, et al. C-Phycocyanin, a selective cyclooxygenase-2 inhibitor, induces apoptosis in lipopolysaccharide-stimulated RAW 264.7 macrophages

19. As Source 3
20. As Source 1
21. As Source 1

22. Finamore A, et al. Antioxidant, Immunomodulating, and Microbial-Modulating Activities of the Sustainable and Ecofriendly Spirulina