Spirulina is a blue-green vegetable alga, and an abundant source of protein, amino acids, phytonutrients, iron, antioxidants and B-vitamins.   M. Eric Gershwin, from University of California/Davis (UCD; California, USA), and colleagues studied 40 seniors, mean age 63 years, wjo took 6 tablets of 500mg spirulina daily for 12 weeks.  The team measured Immune function via  complete blood cell (CBC) counts and indoleamine 2,3-dioxygenase (IDO) enzyme activity, with results showing that over half of all participants receiving spirulina had higher IDO activity after 6 and 12 weeks; in particular, this effect was striking in men, with over 75% of study subjects manifesting the benefit. Further, spirulina was associated with a steady increase in corpuscular hemoglobin, thereby aiding to “ameliorate anemia and immunosenescence in older subjects.”