Spirulina is cyanobacterium (blue-green algae) that grows in alkaline water. Spirulina is rich in protein and nutrients and been used as a food source in Africa for centuries. Today, spirulina powders and capsules are popular nutritional supplements. And, the rich antioxidant properties and therapeutic benefits are not just for people. Preliminary research in Australia has shown that livestock feed that's been enhanced with nutritious spirulina to improve growth, fertility, aesthetic and nutritional quality in farm animals. 
Top Benefits of Spirulina
Spirulina and Eye Health
Spirulina is a rich dietary source of zeaxanthin, a xanthophyll. Xanthophyll are substances similar to carotenes, the pro-eye compounds found in carrots. Zeaxanthin is a xanthophyll that has nutritional importance to human eyes in that sufficient intake may reduce risk of cataracts and age-related macular degeneration. Observational studies have shown a connection between adequate zeaxanthin and lower incidence of age-related macular degeneration. 
Spirulina and Liver Health
Incidence of non-alcoholic fatty liver disease is on the rise. It is often a side effect of obesity and poor diet that occurs when a fat overload in the liver is coupled with oxidative stress. The best strategy against it is to lose any excessive body weight (fat) and make the appropriate dietary changes that will help decrease lipid levels. Additionally, supplementing with spirulina may support a boost in fatty acid oxidation.  Many, many animal models have shown spirulina to promote liver health by lessening redness through anti-oxidative mechanisms.  
A Chinese study involving mice showed that supplementation of spirulina and vitamin C could reduce enzyme activity known to be damaging to the liver. No surprise, the effect was credited to the antioxidant levels. 
Spirulina and Brain Health
You may have heard of the "blood-brain barrier", it is a separation of the brain and spinal cord from the other organs in the body. This natural mechanism is in place to keep infections from reaching your most vulnerable tissues. Your brain contains microglia cells that are the immune system for your nervous system. It's the job of these microglia cells to constantly scavenge your central nervous system for plaque, damaged neurons, and harmful agents. When harmful agents do manage to cross the blood-brain barrier, microglial cells spring into action for defense. However, activated microglia produce redness and in the brain, which is thought to be a major component in the development of degenerative brain diseases. Spirulina may be beneficial and provide resistance to the oxidative aspect of microglial cell activation.  Research by the Department of Otolaryngology at Buddhist Dalin Tzu-Chi General Hospital in Taiwan found similar oxidation-reduction properties in Spirulina and even stated that these properties may fight against memory loss. 
The Dietary Supplements Information Expert Committee of the United States Pharmacopeial Convention undertook a safety evaluation of spirulina and assigned a Class A safety rating.  Spirulina is generally considered safe and is backed by a long history of use as a food source and safety in animal models. However, when purchasing spirulina or any produce you're going to put into your body, it is important to ONLY invest in quality products that are responsibly produced so as to avoid contamination and guarantee safety. 
- Holman BW, Malau-Aduli AE. Spirulina as a livestock supplement and animal feed. J Anim Physiol Anim Nutr (Berl). 2012 Aug 2. doi: 10.1111/j.1439-0396.2012.01328.x.
- Yu B, Wang J, Suter PM, Russell RM, Grusak MA, Wang Y, Wang Z, Yin S, Tang G. Spirulina is an effective dietary source of zeaxanthin to humans. Br J Nutr. 2012 Aug;108(4):611-9. doi: 10.1017/S0007114511005885. Epub 2012 Feb 7.
- McCarty MF. Full-spectrum antioxidant therapy featuring astaxanthin coupled with lipoprivic strategies and salsalate for management of non-alcoholic fatty liver disease. Med Hypotheses. 2011 Oct;77(4):550-6. doi: 10.1016/j.mehy.2011.06.029. Epub 2011 Jul 20.
- Pak W, Takayama F, Mine M, Nakamoto K, Kodo Y, Mankura M, Egashira T, Kawasaki H, Mori A. Anti-oxidative and anti-inflammatory effects of spirulina on rat model of non-alcoholic steatohepatitis. J Clin Biochem Nutr. 2012 Nov;51(3):227-34. doi: 10.3164/jcbn.12-18. Epub 2012 Oct 12.
- Selmi C, Leung PS, Fischer L, German B, Yang CY, Kenny TP, Cysewski GR, Gershwin ME. The effects of Spirulina on anemia and immune function in senior citizens. Cell Mol Immunol. 2011 May;8(3):248-54. doi: 10.1038/cmi.2010.76. Epub 2011 Jan 31.
- Bhattacharyya S, Mehta P. The hepatoprotective potential of Spirulina and vitamin C supplemention in cisplatin toxicity. Food Funct. 2012 Feb;3(2):164-9. doi: 10.1039/c1fo10172b. Epub 2011 Nov 28.
- Pabon MM, Jernberg JN, Morganti J, Contreras J, Hudson CE, Klein RL, Bickford PC. A spirulina-enhanced diet provides neuroprotection in an α-synuclein model of Parkinson's disease. PLoS One. 2012;7(9):e45256. doi: 10.1371/journal.pone.0045256. Epub 2012 Sep 18.
- Hwang JH, Lee IT, Jeng KC, Wang MF, Hou RC, Wu SM, Chan YC. Spirulina prevents memory dysfunction, reduces oxidative stress damage and augments antioxidant activity in senescence-accelerated mice. J Nutr Sci Vitaminol (Tokyo). 2011;57(2):186-91.
- Marles RJ, Barrett ML, Barnes J, Chavez ML, Gardiner P, Ko R, Mahady GB, Low Dog T, Sarma ND, Giancaspro GI, Sharaf M, Griffiths J. United States pharmacopeia safety evaluation of spirulina. Crit Rev Food Sci Nutr. 2011 Aug;51(7):593-604. doi: 10.1080/10408391003721719. Review.
- Deng R, Chow TJ. Hypolipidemic, antioxidant, and antiinflammatory activities of microalgae Spirulina. Cardiovasc Ther. 2010 Aug;28(4):e33-45. doi: 10.1111/j.1755-5922.2010.00200.x. Review.
†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.