Understanding and being able to identify spirulina side effects is important if you are adding this nutrient-dense substance to your regular diet.
Spirulina is a blue-green micro-algae that has been consumed as a food source for centuries, and recently became popularly known as a ‘superfood.’, according to a research published by O. Ciferri in the American Society of Microbiology. Proponents of spirulina tout that it has more protein than chicken or beef, as well as 9 essential amino acids and many vitamins and nutrients. It is also known as a detoxifier, helping to oxygenate the blood and flush out dangerous toxins from the body. 
Spirulina Side Effects
However, like almost all supplements, consuming too much can result in spirulina side effects such as liver toxicity, nausea, kidney stones, stomach pain, and motor neuron diseases. It is not only important to know your own sensitivity to spirulina, but it’s also important to know where this superfood is sourced and how it is grown. Although spirulina can certainly be part of a healthy diet, be aware of the possible side effects.
Heavy Metal Toxicity
Like seafood, spirulina that is grown in the wild can be contaminated with arsenic, mercury, or other heavy metals according to research conducted by Siva Kiran R.R., Department of Biotechnology, MS Ramaiah Institute of Technology, Bangalore. Children are especially at risk for developing symptoms of heavy metal poisoning, which include abdominal pain, nausea, anemia, and central nervous system dysfunction. 
Metabolizing spirulina creates ammonia, which is converted into urea. Excessive amounts of spirulina can cause your kidney to overload from flushing out the urea, which can lead to kidney stones or even kidney failure, in the most serious cases.
Body Weight Fluctuation
Spirulina contains a large amount of iodine, which is normally an essential part of a healthy diet. However, this concentration of iodine can affect your thyroid glands, so it’s not recommended for anyone suffering from thyroid disease or hyperparathyroidism. Excessive use of spirulina can also cause edema, a build-up of fluid in your limbs. Edema can affect your absorption of calcium, cause weight gain, and create feelings of lethargy.
Eating spirulina can cause debilitating flatulence, leading to painful abdominal cramps or nausea. Consuming unregulated spirulina that has been harvested from the wild can also put you at risk from microcystins, toxins created by blue-green algae varieties that are easily mistaken for spirulina, which can cause indigestion and dehydration, according to a Liverpool University study, Liverpool, UK.
Motor Neuron Disease
Motor neuron disease, also known as MND, is a severe neurodegenerative disease that can be caused by the neurotoxic chemicals in similar strains of blue-green algae as per a report published by Audrey Roy-Lachapelle, M.S., Department of Chemistry, Université de Montréal. For this reason, knowing the source of your spirulina is always paramount. Eating unregulated, wild-harvested spirulina can lead to MND, Parkinson’s and dementia, while even the less serious consequences, such as anxiety and insomnia, should not be ignored if they begin to appear.