There is general agreement amongst health professionals and dieticians that manganese is essential to ensure the health and well being of humans and animals. The human body contains from 12 to 20 milligrams of manganese. Estimations of the human requirements for manganese vary considerably, but are based on studies of the balance between intake and excretion necessary to maintain this level.
Data from several studies suggest that manganese intake of from 0.035 to 0.070 milligrams per kilo of body weight provides the needed balance. However, a 1988 study conducted by researchers at the University of Texas at Austin found that a minimum of 3.5 milligrams per day seems necessary.
Human consumption depends on the amount of certain foods consumed. The typical English winter diet (with substantial tea intake) provides up to 8.8 mg of manganese per day, while studies of women in Japan, Canada, New Zealand and the USA suggest average daily intakes from 2.5 to 4 mg per day.
Manganese deficiency has been demonstrated in animals and has been noted in humans in association with vitamin K deficiency. Its main manifestations in all species studied are impaired growth, skeletal abnormalities, disturbed or depressed reproductive functions, lack of muscular coordination among newborns and defects in lipid and carbohydrate metabolisms.