Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

Meredith Bull, ND, is a licensed naturopathic doctor with a private practice in Los Angeles. She helped co-author the first integrative geriatrics textbook, "Integrative Geriatric Medicine."

Spirulina is a type of blue-green algae that is rich in nutrients, including B vitamins, beta carotene, and vitamin E. It is cultivated for use both as a dietary supplement and as a whole food. Spirulina is a good source of vegan protein and is thought to have other health benefits, some of which have been proven and others that have not.

This article takes a closer look at the evidence supporting the use of spirulina as a dietary supplement and whether it delivers on its health claims.

Beyond its nutritional value, spirulina is used in complementary and alternative medicine to treat a number of health conditions. Spirulina contains certain compounds that may benefit your overall health, including antioxidants, minerals, chlorophyll, and phycocyanin (the pigment which gives the algae its blue color).

These and other compounds are believed by some to prevent or treat a variety of medical conditions, including:

To date, there are few studies that strongly support these claims. With that said, there is some evidence of spirulina's health benefits.

Spirulina shows some promise in treating high cholesterol and high triglycerides, according to a study in the Annals of Nutrition and Metabolism.

For this study, 78 healthy older adults were given either a spirulina supplement or an inactive placebo. After four months, the adults given spirulina had greater reductions in cholesterol than those given the placebo.

The researchers believe that antioxidants found in spirulina, including phycocyanin, were responsible for this effect.  

Spirulina may help relieve symptoms of allergic rhinitis (hay fever), according to a small study conducted at Eskisehir Osmangazi University in Turkey. When compared to participants who were given a placebo, those given spirulina were reported to have greater relief of sneezing, stuffy nose, nasal discharge, and itching.

Even so, the researchers were unable to say how spirulina was able to relieve these hay fever symptoms.

A small study published in Nutrition Research and Practice found that spirulina may improve insulin sensitivity and lower total cholesterol levels in people with type 2 diabetes.

After taking a daily spirulina supplement for 12 weeks, 37 adults with diabetes not only had improved glucose (blood sugar) control but also saw reductions in their cholesterol, triglycerides, and blood pressure.

Some people believe that phycocyanin in spirulina has strong anti-cancer effects. As far-fetched as the claim may seem, there is some evidence of this effect in people with oral (mouth) cancer.

According to a small study published in Nutrition and Cancer, 44 tobacco chewers with precancerous oral lesions were given either a daily dose of spirulina or a placebo. After 12 months, 20 of the 44 participants given spirulina had a decrease in the size of their lesion, compared to three of the 43 participants who were given a placebo.

While the results seemed promising, a 2011 review in Evidenced-Based Complementary and Alternative Medicine said that the study was flawed and concluded that the findings "cannot be regarded as evidence of a positive effect."

There is some weak evidence that spirulina can aid in the treatment of high cholesterol and type 2 diabetes. Other claims, including spirulina's anti-allergy and anti-cancer effects, have yet to be proven.

Although spirulina is generally safe to use, it can cause headaches, muscle pain, sweating, and insomnia in some people. Others have been known to be allergic to spirulina, particularly those with allergies to seafood, seaweed, and other sea vegetables.

Because spirulina is thought to stimulate the immune system, it should be avoided in people with autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, or lupus. In these diseases, an overactive immune system attacks healthy tissues.

For this same reason, spirulina should be avoided in people taking immunosuppressive drugs like Cellcept (mycophenolate), Enbrel (etanercept), and Humira (adalimumab). These drugs treat diseases by blocking the immune system in specific ways. Spirulina theoretically could make the medications less effective.

People with a disorder called phenylketonuria , who are unable to process a certain amino acid, should also avoid spirulina because it is rich in amino acids.

The safety of spirulina in pregnant or nursing people has not been established. Speak with your doctor before using spirulina if you are pregnant, breastfeeding, or planning to get pregnant.

Spirulina is generally safe for use but may cause allergy, headaches, insomnia, muscle pain, and sweating in some. Spirulina should be avoided in pregnant or nursing people, people with autoimmune diseases or on immunosuppressants, and those with phenylketonuria.

There is no recommended effective dosage of spirulina.

Some studies have shown that doses of up to 3,000 milligrams (mg) per day were safe and well tolerated for up to 12 months with no notable side effects.

Manufacturer recommendations vary but, as a general rule, never exceed the dosage on the product label.

Spirulina is often sold in powder form but is also available in capsules, tablets, and liquids. The powder is sometimes added to smoothies.

The appropriate dose can vary based on your age, sex, medical history, and other factors. Speak to your health provider for advice on the dose that's right for you.

There is no recommended dose for spirulina. As a general rule, never exceed the dosage on the product label.

There are many blue-green algae species referred to as "spirulina," but those used in supplements are most often Aphanizomenon flos-aquae, Spirulina maxima, or Spirulina platensis.

Certain "wild-crafted" spirulina products may have been grown in water contaminated with heavy metals or other pollutants. To be safe, opt for supplements produced in labs and certified by third-party authorities like U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

A seal of approval from these organizations does not mean that the supplement is either safe or effective. It simply means that it contains the ingredients on the product label and that no contaminants have been found.

Spirulina is a blue-green algae that has some nutritional value but is also thought by some to have health benefits. This includes the prevention or treatment of allergies, diabetes, fatigue, high cholesterol, and even certain cancers.

While most of these claims are poorly supported by research, there is weak evidence that spirulina can help lower cholesterol or aid in the control of blood sugar.

Spirulina is generally safe to use but may cause allergy, headaches, insomnia, muscle pain, and sweating in some. Because of its possible effect on the immune system, spirulina should be avoided in people with autoimmune diseases or on immunosuppressive therapies. Pregnant and nursing people or those with phenylketonuria should also avoid spirulina.

Always opt for spirulina supplements certified by third-party authorities like ConsumerLab, NSF International, or U.S. Pharmacopeia (USP). There is no recommended dose for spirulina.

As with all supplements, it's important to talk with your health provider before using spirulina to determine if it's appropriate for you and if there are any interactions that may cause you harm.

It is important to remember that just because a remedy is "natural" doesn't mean that it is safe.

Spirulina is a nutrient-dense blue-green algae used as a nutritional supplement. It is claimed to help reduce fatigue and boost energy, lower cholesterol and triglyceride levels, stimulate the immune system, fight viral infections, and aid in weight loss.

Spirulina rarely causes side effects, but the potential side effects include headaches, muscle pain, sweating, and insomnia. Some people can be allergic to spirulina and may experience an allergic reaction.

People who should not take spirulina include those: 

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Karkos PD, Leong SC, Karkos CD, Sivaji N, Assimakopoulos DA. Spirulina in clinical practice: evidence-based human applications. Evid Based Complement Alternat Med. 2011;2011:531053. doi:10.1093/ecam/nen058

Park HJ, Lee YJ, Ryu HK, Kim MH, Chung HW, Kim WY. A randomized double-blind, placebo-controlled study to establish the effects of spirulina in elderly Koreans. Ann Nutr Metab. 2008;52(4):322-8. doi:10.1159/000151486

Cingi C, Conk-Dalay M, Cakli H, Bal C. The effects of spirulina on allergic rhinitis. Eur Arch Otorhinolaryngol. 2008;265(10):1219-23. doi:10.1007/s00405-008-0642-8

Lee EH, Park JE, Choi YJ, Huh KB, Kim WY. A randomized study to establish the effects of spirulina in type 2 diabetes mellitus patients. Nutr Res Pract. 2008;2(4):295-300. doi:10.4162/nrp.2008.2.4.295

Mathew B, Sankaranarayanan R, Nair PP, et al. Evaluation of chemoprevention of oral cancer with Spirulina fusiformis. Nutr Cancer. 1995;24(2):197-202. doi:10.1080/01635589509514407

Mani UV, Desai S, Iyer U. Studies on the long-term effect of spirulina supplementation on serum lipid profile and glycated proteins in NIDDM patients. Journal of Nutraceuticals, Functional & Medical Foods. 2000;2:3, 25-32. doi:10.1300/J133v02n03_03

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