Manganese and Human Health
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.
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.
The following fresh food groups (in descending order) are most important in manganese content : nuts, whole cereals, dried fruits, roots, tubers and stalks, fruits, non-leafy vegetables, meat, poultry products, fish and seafoods. Leafy vegetables also rank high on the list when expressed in dry-weight terms. Tea has a very high manganese content, ten times that of cereals.
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.
Manganese, like anything else, when in excess has been demonstrated in animals and highlighted in some epidemiological studies to cause subtle sub-clinical neurological effects if inhaled in excess or in small amounts over a long period of time. Exposure via the gut, on the other hand has been shown in similar studies to be tightly controlled by homeostatsis.
Manganese and Animal Health
Grazing cattle do not seem to suffer from manganese shortage, probably because their manganese requirements are met by the herbage they consume. Manganese deficiency is a more serious problem in domestic animals such as poultry, non-grazing cattle and pigs. The main reason for this is that protein supplements of animal origin (dried milk, fish meal, mean meal) are usually low in manganese.
To promote strong legs in poultry, and to keep up normal egg production, it is necessary to supplement their feed with about 40 mg of manganese per kilo of weight. For ruminants, the requirement for optimal skeletal development is only 20-25 mg/kilo. Soybean meal, important in poultry raising, contains 30 to 40 ppm manganese.