Spirulina's effect on heart health

Spirulina is a type of cyanobacteria (blue-green algae), single-celled microbes that can get energy from sunlight, like plants, and are found worldwide in fresh and saltwater. Spirulina has been used as a food source for centuries, even as far back as ancient Aztec civilizations (Karkos, 2011).

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Considered a “superfood” by some, spirulina is a good source of protein and vitamins; it is approximately 55–70% protein, making it an alternative protein source for vegans and vegetarians. Spirulina contains both essential and non-essential amino acids; essential amino acids are compounds that we need, but are unable to make ourselves and have to come from our diet. The essential amino acids found in spirulina include leucine, tryptophan, methionine, phenylalanine, lysine, thionine, isoleucine, and valine. In addition to being a great source of protein, spirulina also has other vitamins and minerals, including (Wikipedia, n.d.):

The main bioactive compound in spirulina is phycocyanin. Not only does this compound give spirulina its distinctive blue-green color, but it also has the potential to promote heart health via anti-inflammatory and antioxidant effects. Spirulina may be beneficial in the treatment of high blood pressure, high cholesterol, and heart disease.

Blood pressure

Research suggests that spirulina promotes vasodilation (opening of the blood vessels) by enhancing nitrous oxide release, leading to a decrease in blood pressure (Torres, 2007). Studies have shown a decrease in blood pressure in people given large (4.5 g) doses of spirulina over six weeks (Torres, 2007). However, more research is needed to better understand the role spirulina may play in the treatment of blood pressure. 

Elevated cholesterol

Non-human studies found that spirulina, due to its phycocyanin, can decrease the amount of cholesterol that the intestines absorb (Torres, 2007). Another proposed mechanism is that spirulina’s antioxidant actions also work to lower cholesterol and triglycerides in the blood. Studies show that people treated with spirulina see a drop not only in their total cholesterol levels but also in their triglyceride and LDL (“bad” cholesterol) levels (Huang, 2018; Mazokopakis, 2014). While not the primary treatment of high cholesterol, spirulina may be beneficial as an added supplement.

Preventing heart disease

Cardiovascular (heart) disease is a leading cause of death, and risk factors for this include elevated blood pressure and cholesterol levels. In addition, the development of atherosclerosis (fat-deposit) plaques on the inside of your arteries puts you at higher risk for heart attacks and strokes. By reducing oxidative damage through its antioxidant actions, increasing blood vessel relaxation via nitrous oxide release, and decreases cholesterol, spirulina can help decrease your risk of heart disease.

With all of these potential effects on heart health, more research is needed to understand spirulina’s role in these conditions better.

Spirulina may be beneficial not only for the heart but also for other systems in the body:

Antioxidant activity

The phycocyanin in spirulina works to fight free radicals that can cause oxidative damage in the body, leading to diseases like cancer, heart disease, inflammatory disorders, etc.

Anti-inflammatory activity

Spirulina appears to have anti-inflammatory effects by decreasing some of the pro-inflammatory signals in your body (Shih, 2009).

Immune booster

Studies have shown that spirulina can increase the activity of natural killer (NK) cells; these are the immune cells in your body responsible for killing tumor cells and cells infected by viruses (Nielson, 2010). 

May increase endurance

Research is limited, but it does suggest that spirulina may increase exercise endurance (Kalafati, 2010). Since exercise produces oxidants that lead to fatigue, the antioxidant action of spirulina may be beneficial in improving endurance. 

May help control blood sugar

Studies have shown that some people taking spirulina have a drop in their fasting blood glucose levels as well as a small reduction in their hemoglobin A1C levels, a blood marker used to measure diabetes severity (Huang, 2018; Parikh, 2001).

May support mental health

Spirulina is a good source of tryptophan, an essential amino acid. Tryptophan plays an important role in your mental health because it is one of the building blocks of the brain chemical serotonin (Sasie, 2018). Low levels of tryptophan and serotonin can lead to conditions like depression, anxiety, etc. Taking spirulina can boost your tryptophan levels and, potentially, your mental health. However, more research in this area is needed.

May improve allergy symptoms

In addition to the other anti-inflammatory effects, spirulina also decreases histamine release, which can lead to a decrease in allergy symptoms. One study showed that people with allergic rhinitis who took spirulina had a significant improvement in the allergy symptoms of runny nose, sneezing, nasal congestion, and itching compared to those who took the placebo (Cingi, 2008).

Spirulina is available in either powder or capsule form. As a powder, you can add it to drinks, sprinkle it on your food, or come up with your own way of incorporating it into your diet. As for how much to take, there is no standard dosing regimen; doses of 1–8 grams have been used in the various studies depending on the condition they are addressing. For high blood pressure, studies have used 2–4.5 grams of spirulina (MedlinePlus, 2019).

Spirulina is generally considered safe; side effects are usually mild and include nausea, vomiting, diarrhea, abdominal discomfort, headache, dizziness, and fatigue. However, there are potentially serious risks with using spirulina, including (MedlinePlus, 2019):

• Toxic contaminants: Spirulina is available both in farmed and natural forms. Make sure that you are getting it from a reputable source and controlled environment. If it is grown in contaminated water, it can have microcystins, toxic metals, and harmful bacteria; microcystins can damage your liver if too much is ingested.

• Unknown effects in children and pregnant or lactating women: We do not know if spirulina is safe for these groups, so it is best to avoid taking spirulina in these situations. 

• Worsening of auto-immune disease: Since spirulina may boost your immune system, you should avoid taking it if you have an auto-immune condition, like multiple sclerosis, lupus, rheumatoid arthritis, etc. Activating your immune system may increase the symptoms of these conditions.

• Blood clotting problems: Although no human studies have shown a decrease in clotting, spirulina does seem to have an anticoagulant (anti-clotting) effect in non-human studies. Therefore, if you have a blood clotting disorder or are taking a blood thinner, you may have increased bruising and decreased clotting ability with spirulina. 

• Phenylketonuria: Spirulina contains the amino acid phenylalanine. This is not a problem for most people, but it can be harmful to people with phenylketonuria (PKU). Those with PKU cannot metabolize phenylalanine, and it builds up in their body and causes health problems. If you have PKU, you should not take spirulina.

• Allergic reactions: It is possible to be allergic to spirulina, so consider allergy testing prior to starting the supplements.

Spirulina is a relatively safe natural supplement that is a good source of proteins, vitamins, and minerals. More research is needed to say definitively how beneficial it is for your heart and overall health. In the meantime, be sure to talk with your healthcare provider before starting any new supplements.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

November 10, 2019

Written by

Chimene Richa, MD

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.