Some species of blue-green algae, including some which are occasionally sold as nutritional Spirulina are capable of producing nasty toxins which can make people very ill indeed. These spirulina products are produced from other species of blue-green algae, and not from Arthrospira platensis and Arthrospira maxima. The main species of blue-green algae which is responsible for this is Microcystis aeruginosa. This species produces potentially very dangerous toxins known as microcystins. Unfortunately, this species often grows in the same places as another species known as Aphanizomenon flos aquae, which is harvested from the wild for human supplements by some companies.
There have also been reports of spirulina products coming from China which have been found to be contaminated with microcystins. Again, this is in all likelihood because the algae is being harvested from the wild. Harvesting from the wild can also bring with it other contaminants such as mercury. This is however nothing to worry about as long as you completely avoid spirulina products containing Aphanizomenon flos aquae, completely avoid spirulina products containing any spirulina harvested from the wild (since it is very difficult to guarantee no contamination) and stick to spirulina products made from Arthrospira platensis or Hawaiian Spirulina Pacifica® which are intentionally grown under very controlled conditions to avoid cross-contamination with other species.
Make sure that you buy from reputable sources and from companies which stick to strict guidelines (for example suppliers that have obtained ISO 9000 certification, have had their products FDA reviewed, comply with pharmaceutical GMP standards etc.) This is no more caution than people should take when purchasing any product which they intend to consume. I am sure that most people would not choose to buy drugs from dodgy online pharmacies. (See here for sources)
There are however some people for whom spirulina is not recommended at all:
- People with auto-immune diseases, and people taking medication designed to suppress the immune system. This is because spirulina can increase the activity of the immune system.
- Women who are pregnant or breast-feeding have been advised to avoid taking spirulina until more research has been done.
- People suffering from Phenylketonuria should not take spirulina as it contains phenylalanine.
As far as general side effects go, there have been reported cases of people experiencing elevated body temperature and changes in digestive activity when beginning using the product. This is however unlikely if spirulina is taken at recommended doses. It is generally believed to be due to the intense doses of nutrients that the body is processing and soon settles down. If you are concerned about any spirulina side effects then reduce the dose.
Other than this, spirulina is generally considered a safe and healthy product with great potential benefits that are still being investigated. True Hawaiian Spirulina Pacifica® has been FDA reviewed and classed as Generally Recognised as Safe (GRAS) for use in foods. Examples of organisations that are supporting spirulina research include:
- The UN, who recognised early on the potential for spirulina to be used in the fight against global malnutrition and as such formed the Intergovernmental Institution for the Use of Micro-Algae Spirulina Against Malnutrition.
- NASA, who have suggested that spirulina could be a very useful food resource for cultivation during long distance space travel