Spirulina is a blue-green algae which is used as a nutritional supplement in many regions of the world. Blue-green algae, also known as cyanobacteria, are famous for thriving in very harsh conditions, and they often store large amounts of nutrients to sustain themselves when their environment is compromised. These stored nutrients can benefit people who consume spirulina, although studies seem to suggest that you would need to eat a rather large amount of this algae to get any benefits from it.
People in Mesoamerica have been using spirulina as a dietary supplement for centuries, as have inhabitants of some regions of Africa. This algae inhabits brackish lakes naturally, and they can also be easily cultivated to increase a yield of algae. Historically, people used this algae to dress their food and to supplement meager diets, and it continues to be used for this purpose in some developing nations. Health food fans eat it because they believe it is a valuable food supplement, consuming spirulina tablets, powders, and drinks.
Depending on the growing conditions, spirulina can be as much as 70% protein, and the protein is complete, rather than partial, as is the case with most proteins of plant origin. It also contains vitamins and nutrients like iron, calcium, vitamin B, magnesium, zinc, and beta carotene, among others. However, one must eat a significant serving of algae each day to really benefit from its nutritional value, rather than having a small sprinkle now and then.
Numerous claims are made about the miraculous abilities of this algae to treat a range of medical problems. The National Institutes of Health in the United States generally give a “C” grade to most of these health claims, meaning that there is “unclear scientific evidence” to support use of spirulina to treat things like viral infections, malnutrition, diabetes, high cholesterol, and eye disorders, among others. However, this doesn't necessarily mean that eating it is a bad thing, and most health food stores make it readily available in an assortment of forms for people who want it.
Pure spirulina has a slightly mossy flavor, and it can taste a bit marine, depending on how it is cultivated. Some people enjoy the flavor, along with the texture, which tends to be a bit clumpy. For people who aren't as into the flavor, smell, and texture, it is possible to find tablets and gelcaps, which allow people to ingest spirulina without tasting it.