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Spirulina Side Effects and Danger You Should know

Spirulina is a blue-green algae that contains a range of nutrients such as B-vitamins, beta-carotene, and E-vitamins. Spirulina also includes antioxidants, minerals, chlorophyll, and phycocyanobilins as a source of vegan protein. Despite having several benefits, you may wonder if there are spirulina side effects.

What is Spirulina?

Spirulina is fresh-and saltwater-growing blue-green algae. People use it as a food source in certain areas of Mexico and Africa because it carries 60 percent protein by weight, and many vitamins and minerals.

In addition, it is an excellent source of healthy polyunsaturated fats, C-phycocyanin, and beta-carotene antioxidants. As a supplement, it is known for its antibacterial, antioxidant, anti-inflammatory, immune-boosting, and cholesterol-lowering abilities.

Spirulina Danger

Although spirulina is safe, it may have some side effects and downsides for individuals with certain conditions. Spirulina harvested in the wild may contain toxins that pose a significant risk of infection.

If it grows in the water that is contaminated with heavy metals, bacteria, or damaging particles called microcystins, the algae may harbor toxins. They are poisonous to your liver when eaten in enormous quantities. In Italy, North America, and China, microcystin in algae supplements have been discovered and these compounds are an increasing problem for public health.

Spirulina cultivated in controlled environments are smaller in microcystins because researchers have established techniques for removing and limiting the manufacturing of this compound.

Can Slow Blood Clotting

Spirulina has an anticoagulant effect, which means it can thin your blood and boost blood clotting time. When you are wounded, coagulation helps avoid excessive bleeding or bruising.

Spirulina may be hazardous for those taking blood thinners or those with bleeding disorders because it may reduce the capacity of your blood to clot, leading to more bruising and bleeding.

While some studies show that spirulina does not influence blood coagulation time. However, there are little knowledge-based studies about its consequences on individuals who are already taking blood-thinning medication. Therefore, if you have a bleeding disorder or are on blood thinners, you should prevent spirulina to avoid side effects.

Can Worsen Autoimmune Diseases

Because spirulina boosts your immune system, it may worsen certain autoimmune diseases such as lupus, various sclerosis, and rheumatoid arthritis in which your immune system attacks your own body cells.

Spirulina strengthens your immune system by reinforcing immune cells called natural killer (NK) cells that attack perceived cell-level threats. Studies on animals and humans show that this effect can help slow tumor development and reduce inflammation.

However, this algae may increase these conditions by enhancing the NK cells in individuals with autoimmune conditions. Spirulina supplements may cause side effects such as autoimmune reactions that affect your skin and muscles, although these side effects seem very rare. If you have an autoimmune condition, spirulina and other supplements of algae should be avoided.

Other Downsides

Some individuals may have spirulina allergies. Reactions can be deadly in serious cases. According to one research, individuals with other allergies are more likely to respond to spirulina than those without allergies.

To prevent side effects, people with allergies should not consume spirulina supplement or should talk to their doctor before using it. Spirulina and other algae contain phenylalanine. Therefore, an individual with phenylketonuria should strictly avoid it.

Some minor spirulina side effects may include nausea, sleeplessness, and headaches. They still consider spirulina is safe, and most individuals experience no side effects.

Bottom Line

Spirulina may cause side effects in some people. It is best to consult with a health care provider before taking it. To prevent spirulina contaminated with microcystins or toxins, buy only products from trusted brands tested by third-party organizations like the U.S. Consumer lab, or NSF International, Pharmacopeia (USP).


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The fate of microcystins in the environment and challenges for monitoring. Toxins (Basel). 2014.

Detection of the hepatotoxic microcystins in 36 kinds of cyanobacteria Spirulina food products in China. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2008.

Contamination by Microcystis and microcystins of blue-green algae food supplements (BGAS) on the Italian market and possible risk for the exposed population. Food Chem Toxicol. 2012.

Detection of Cyanotoxins in Algae Dietary Supplements. Toxins (Basel). 2017.

Microcystins in water and in microalgae: Do microcystins as microalgae contaminants warrant the current public alarm? Toxicol Rep. 2018.

Enhancement of antitumor natural killer cell activation by orally administered Spirulina extract in mice. Cancer Sci. 2009.

Spirulina elicits the activation of innate immunity and increases resistance against Vibrio alginolyticus in shrimp. Fish Shellfish Immunol. 2016.

Dietary Spirulina platensis enhances humoral and cell-mediated immune functions in chickens. Immunopharmacol Immunotoxicol. 1996.

Antioxidant and anti-inflammatory properties of an aqueous cyanophyta extract derived from Arthrospira platensis: contribution to bioactivities by the non-phycocyanin aqueous fraction. J Med Food. 2015.

Anaphylaxis to Spirulina confirmed by skin prick test with ingredients of Spirulina tablets. Food Chem Toxicol. 2014.

Cyanobacteria: an unrecognized ubiquitous sensitizing allergen? Allergy Asthma Proc. 2011.

Terms of Use: The information on this website is provided for educational purposes only and is not intended to provide personal medical advice. If you have questions about a medical condition, consult your doctor or another qualified health provider. Never ignore professional medical advice because of something you have read on this website. The Nutrition Source on this website makes no product recommendations or endorsements.

Naeem Durrani BSc
I am a freelance health and wellness writer. My interests include medical research, and the scientific evidence around effective wellness practices, which empower people to transform their lives.

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