Spirulina is a natural "algae" (cyanbacteria) powder that is incredibly high in protein and nutrients. When harvested correctly from non-contaminated ponds and bodies of water, it is one of the most potent nutrient sources available. It is largely made up of protein and essential amino acids, and is typically recommended to people who decide to remain vegetarian for its high natural iron content. It is often touted for its high B12 content, though there is a lot of debate about if this particular form is a complete and absorbable form of B12 and it is not recommended completely in place of animal products.
The high concentration of protein and iron also makes it ideal during pregnancy, after surgery, or anytime the immune system needs a boost.
Spirulina is 65% protein and amino acids, including the essential fatty acid gamma linolenic acid (GLA), which has gotten a lot of attention for its anti-inflammatory properties, especially when taken with other quality omega-3 supplements like fermented cod liver oil. It contains all essential amino acids.
Spirulina contains omega 3-,6 and 9s and is especially high in omega-3s.
Spirulina is extremely high in chlorophyll, which helps remove toxins from the blood and boost the immune system.
Spirulina has a very high concentration of bio-available iron and is excellent during pregnancy and for those with anemia and will not cause constipation.
Spirulina is a great source of other nutrients including (according to Wikipedia): "Spirulina contains vitamins B1 (thiamine), B2 (riboflavin), B3 (nicotinamide), B6 (pyridoxine), B9 (folic acid), vitamin C, vitamin D, vitamin A, and vitamin E. It is also a source of potassium, calcium, chromium, copper, iron, magnesium, manganese, phosphorus, selenium, sodium, and zinc. Spirulina contains many pigments, which may be beneficial and bioavailable".
Spirulina (from Mountain Rose Herbs) was tested by an independent laboratory and found to have an ORAC (Oxygen Radical Absorbance Capacity) of over 24,000, which is 4x the ORAC score of blueberries. The ORAC score is generally used to measure antioxidant ability and concentration in different foods.
Spirulina is also incredibly high in calcium with over 26 times the calcium in milk, making it excellent for children, the elderly, and during pregnancy.
Some research has suggested that spirulina may be helpful in allergies and allergic reactions.
Spirulina's phosphorus content makes it helpful as part of a tooth remineralization regimen.
Emerging evidence suggests that it binds with radioactive isotopes and may be useful for radioactivity exposure or radiation therapy.
The protein in spirulina is highly usable and has a net protein utilization rate of between 50-61%.
Spirulina can bind with heavy metals in the body and help remove them.
Spirulina can also increase fat burning during exercise.