Health stores sell the blue-green algae supplement spirulina as a potential treatment for everything from heart disease to diabetes. However, according to MedlinePlus, no medical evidence currently exists to prove any of the health claims concerning spirulina. However, this supplement generally doesn't trigger too many negative health effects in normal doses. Negative facts about spirulina relate to the preparation of the product and its unsuitability for people with certain medical conditions.
Though pure spirulina offers few health risks, the growing algae is highly prone to contamination. Contamination occurs through several natural means, including the mold anatoxin and a toxic substance called microcystin. In addition, the algae absorbs local pollutants such as toxic metals like mercury. In all cases, these contaminants may harm the liver and in some cases can lead to diseases such as cancer. Other adverse symptoms due to contamination include headaches, nausea and weakness. In severe cases the toxins can lead to death. However, reputable suppliers should test the spirulina for pollutants.
A negative fact about spirulina is that it may aggravate symptoms of autoimmune diseases. Some evidence points to spirulina's stimulating affect on the human immune system. This could make conditions such as lupus, arthritis, psoriasis, or multiple sclerosis more pronounced. Similarly, spirulina could interact with medications designed as immune system suppressants including adalimumab, azathioprine or cyclosporine.
Spirulina may negatively affect people with the metabolic condition known as phenylketonuria, or PKU, according to the University of Maryland Medical Center. People with phenylketonuria usually have the condition from birth which suppresses a person's ability to break down phenylalanine, a type of amino acid found in many protein-rich foods. Spirulina contains all the essential amino acids including phenylalanine. This means that as a supplement, it may have the unintended effect of harming a person with phenylketonuria -- leading to symptoms such as seizures or skin rashes over time.
As the NYU Langone Medical Center points out, spirulina contains lots of nutritional benefits -- but at a relatively high price. While spirulina is high in protein, you can get vegetable and plant protein such as beans, soy, grains and nuts for a lower price. You can also get the beta-carotene in spirulina without spending as much by consuming common vegetables such as carrots. Iron is found in spirulina, but you can get a similar dose from dark leafy green vegetables, red meats and fish. Be aware that until medical evidence confirms otherwise, spirulina offers few additional nutritional benefits to a healthy diet.