There are a number of superfoods you already know and love. Whether it is berries, leafy greens or nuts, you have undoubtedly heard of their superb nutrient density and their overall benefits for your health. But what about spirulina? While it has been dubbed a ‘superfood’ and its name may ring a bell, many of us are unfamiliar with the details of what it is, where it comes from and how it affects our overall health. 


So what exactly is spirulina? Spirulina is a cyanobacteria, also known as blue-green algae that grows in both fresh and saltwater. With the rise of its popularity, it has also been commercially grown for use in foods and supplements. Spirulina is 60% protein and contains beneficial polyunsaturated fats as well as antioxidants. It is said to be anti-inflammatory, immune boosting and beneficial for lowering cholesterol. But as with any dietary supplement there are important safety issues to be considered, especially for those with certain conditions that we will be discussing below.

Today we want to talk about our top five safety concerns involved with dietary spirulina to ensure you have a complete picture of this supplement and make an informed decision on whether or not to add it to your diet.

1. Harvested Quality

Spirulina’s quality depends directly on the water it grows in. If said area is polluted, spirulina that is harvested from it may contain heavy metals or harmful bacteria. Prior to purchasing your product, make sure to thoroughly research how and where it was harvested to ensure optimal quality.

2. Microcystins

Much like other forms that have evolved to include defensive mechanisms as part of their survival strategy, spirulina has protective microcystins. Microcystins are toxins produced by cyanobacteria upon cell rupture or death. The toxins are stable in the sunlight, a wide range of temperatures and pH range – meaning they are hard to destroy and can exist even through heat treatment. 

Microcystins are an area of concern due to the fact that they are hepatotoxic, meaning they are harmful to the liver. While the liver may be the main target of microcystins, they are also irritating to the skin, eyes, and throat. 

3. Contamination

If spirulina happens to be contaminated, children are more sensitive to this contamination. To offset this scientists are working to lower the amount of microcystins and remove them from the final product, so spirulina grown in controlled environments may be safer for the human liver. 

4. Immune system interactions

As for the immune boosting properties we mentioned above, spirulina is said to have the ability to strengthen natural killer (NK) cells, which attack perceived threats in the body. However those with autoimmune disorders should be cautioned, as strengthening NK cells in this case can worsen their overall health, given that the immune system is not working properly and attacks the body instead. Spirulina may also weaken the effects of immunosuppressant drugs, so people with autoimmune conditions and those taking immunosuppressive medication should avoid spirulina.

5.Blood clotting effects

Moreover, spirulina has anticoagulant effects which may cause blood to thin and decrease its clotting time. As you already know, clotting is crucial in order to stop bleeding or bruising after an injury. As studies regarding blood thinning drugs are inconclusive at this point, people taking blood thinners or who have a bleeding disorder should avoid using spirulina, as it may decrease clotting time in bleeding and bruising.

It is also important to note that it is possible to have an allergy to spirulina. People with existing allergies should consult with their nutritionist prior to using it. Additionally, spirulina also contains the amino acid phenylalanine, so it is advised that people with the inherited disorder phenylketonuria (PKU) avoid its use. Spirulina may also cause headache, nausea and insomnia. As there is not enough research yet regarding the safety of using spirulina during pregnancy or while breastfeeding, it is best to avoid it during  these times. 

The Good News

The good news is that despite possible side effects, spirulina does offer some health benefits and is generally considered safe for most people when purchased from reliable sources. Ensure you are only purchasing spirulina from trusted distributors and brands that have been tested by third-party organizations, such as U.S. Pharmacopeia (USP), ConsumerLab or NSF International. As with any supplements, it is recommended to check in with your nutritionist or health care practitioner before adding it to your dietary regimen. 

Additionally, there are a number of alternative supplements that offer some of the same benefits as spirulina without negative side effects. Our nutritionists here at Starkel Nutrition would be happy to offer their suggestions and see which products would be best to support your health. Call us at 206-853-0534 today or click here to schedule an appointment with one of our expert nutritionists. 

Written by Yuliya R., Makala T., and student intern Lauren K., Bastyr University