Spirulina Simply Explained

1. What Is Spirulina?

Spirulina is the dried biomass of filamentous cyanobacteria of the genus Arthrospira, especially Arthrospira platensis and Arthrospira maxima. It grows naturally in alkaline soda lakes and is now cultivated in open ponds and closed systems. Traditionally it is eaten as dried cakes; today it serves predominantly as a dietary supplement and as a protein-rich ingredient in foods.

2. Where Is It Found, and What Is It Made From?

Spirulina is found in powder, tablets, capsules as well as in fortified foods and drinks. Fresh or frozen biomass is also available. It is obtained by cultivation in alkaline nutrient solutions, harvesting of the filaments and gentle drying into a dark green powder. In studies, predominantly the dried whole biomass is tested.

3. What Does Spirulina Do? What Research Shows

Body Weight and Body Composition

Review articles show that spirulina can somewhat lower body weight; individual studies reach different results. Body fat percentage also fell in some investigations 153447. Appetite decreased in one study compared with baseline 34. In malnourished children, by contrast, spirulina led to weight gain 3. Individual studies found no difference in weight or body measurements 24263743. Many studies are small and short, so the informative value remains limited.

Blood Lipids

Several review articles show that spirulina can lower total cholesterol, LDL cholesterol and triglycerides 45141920. HDL cholesterol also rose in some studies 2331. In overweight men, these improvements appeared mainly together with training 3238. A meta-analysis (joint evaluation of many studies) and some studies, however, found no differences 74144. The optimal amount and the significance of the species remain open.

Blood Glucose and Metabolism

Meta-analyses show that spirulina can lower fasting blood glucose, also in type 2 diabetes 1920. Randomized (participants assigned by lot) studies confirmed this in type 2 diabetes, HIV infection and Alzheimer's dementia 223031. Insulin resistance and insulin levels also improved in several studies, in one of them with and without interval training 143049. Insulin sensitivity improved in some investigations 303542. Sauces fortified with spirulina did not change blood glucose levels in fatty liver and type 2 diabetes 3739. Many studies are small and short.

Oxidative Stress and Antioxidants

Controlled studies (with a comparison group) found less oxidative damage, measured by malondialdehyde or TBARS 293751. Total antioxidant capacity was also higher in several studies 25272937. Inflammatory markers such as interleukin-6 and hs-CRP improved in a meta-analysis and some studies 143034. In a study with salad dressing, antioxidant capacity and hs-CRP did not change in any group 36. Many studies include small groups and short durations.

Physical Performance

A randomized crossover trial with Arthrospira maxima in overweight men found a higher maximal oxygen uptake, with and without a training program 334748. Time to exhaustion was prolonged in two studies 4751. In the study with Arthrospira maxima, lactate accumulation set in later 4748. Another study found more hemoglobin than with placebo (sham agent) 45. By contrast, a study in rugby players found only a small, non-confirmed advantage in jumping and sprinting 43. A systematic review (structured summary of all studies) reports a better oxygen uptake at submaximal exercise, but no difference in strength athletes 18.

Blood Pressure

Several review articles found a lower diastolic blood pressure with spirulina, especially in high blood pressure and overweight 578121420. Systolic blood pressure also fell in several review articles 81214. Three small studies saw a reduction only within the spirulina group 364046. Vascular function improved in overweight people with high blood pressure compared with baseline 40. However, four randomized trials found no differences in blood pressure 26283741. The positive findings come predominantly from short studies with small groups.

Allergic Conditions (e.g., Allergic Rhinitis)

A systematic review found less runny nose, blocked nose and itching in allergic rhinitis. The authors rate the evidence (body of evidence) as very low because of only two studies 9. The findings are based mainly on review articles. Larger randomized studies stating species, form and amount are still pending.

Other Investigations

Investigated were predominantly Arthrospira platensis in the form of powder, capsules and tablets as well as fortified foods. Mixtures with other microalgae or additives cannot be attributed to spirulina alone. The transferability to other spirulina species and forms as well as long-term effects remain open.

4. How Was Spirulina Taken in the Studies?

In the studies, participants usually took spirulina as dried powder of the whole biomass. Tablets, capsules or foods and drinks fortified with it also occurred. Investigated were mainly Arthrospira platensis and Arthrospira maxima. The amounts tested are shown in the table. Some studies tested mixtures, for example with chlorella, other algae, turmeric or together with training. In such mixtures, it cannot be said which share of the effect comes from the spirulina alone.

5. Is Spirulina Safe? Side Effects in the Studies

Tolerability is described predominantly as good in the studies; in some cases no side effects were observed 21. Individual studies reported a slight increase in creatinine 2427. A skin gel with spirulina extract caused only very few local side effects 50. Review articles describe rare hypersensitivity reactions to spirulina up to anaphylaxis 5253. In mixed preparations with several algae or additives, a result cannot be attributed to spirulina alone.

All details with tables and sources: full expert page on Spirulina