Spiruina most often is considered a health food, but there may be little-known dangers lurking within this popular blue-green algae. While spirulina might help promote good health though its complete nutritional profile, do not overlook the dangers associated with this nutritional supplement. The risks are related to the fact that spirulina is grown in water that potentially can be contaminated with dangerous substances.

Spirulna Uses

Spiulina is rich in vitamins, minerals and antioxidants that help protect the body from damage. In addition, spirulina is 62 percent amino acids, making it high in protein. The University of Maryland Medical Center says spirulina is used to improve immune function, boost the growth of healthy bacteria, known as probiotics, and treat liver disorders, allergies and infections. While spirulina is not officially approved to treat or prevent any disease, its high concentrations of nutrients make it useful for supporting good health.

Contamination by Toxins

All types of blue-green algae can become contaminated with toxins known as microcystins, the University of Maryland Medical Center warns. Blue-green algae, also known as cyanobacteria, release toxins when they die. Of these toxins, microcystins are of the greatest concern, due to the fact that they are toxic to the liver, the U.S. Environmental Protection Agency notes. In addition, microcystins can irritate the skin, eyes and throat. MedlinePlus reports that contaminated blue-green algae can cause a number of symptoms, including nausea, vomiting, stomach pain, thirst, weakness, liver damage and death.

Contamination by Heavy Metals

Another potential danger of spirulina is heavy metal contamination. The University of Maryland Medical Center notes that heavy metals in the water can be absorbed by algae. One study published in 2013 in "Saudi Journal of Biological Sciences" sampled 25 commercial spirulina products and found concentrations of six heavy metals. Study authors say lead, mercury, cadmium and arsenic are most likely to contaminate spirulina products. Each of these heavy metals can produce organ damage, even at lower levels of exposure.

Choosing a Safe Spirulina Product

To avoid the dangers of spirulina, purchase it from a trusted manufacturer. One way to do this is to look for seals that represent third-party testing -- for example, the NSF seal indicates that the seller uses Good Manufacturer Practices, a set of quality guidelines set by the National Sanitation Foundation. Alternatively, you can look for a USP seal, which means the product has been verified by U.S. Pharmacopeial Convention, a scientific, nonprofit organization that sets quality standards for supplements and medicines.