Manganese and the Human Body

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.

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.

The wide range of manganese contained in cereal grains and products depends on the species and on the milling process used. In a US study, wholewheat containing 31 ppm manganese yielded 160 ppm in the germ, 119 ppm in the bran and only 5 ppm in the white flour.

Half a cup of oatmeal, 30 grams of shredded wheat or raisin bran cereal, a quarter of a cup of pecans or a third of a cup of peanuts, and half a cup of cooked spinach, contain each over a milligram of manganese.

Sweet potatoes, red lima or navy beans and pineapple juice are other sources. There is very little or no manganese present in dairy products and highly refined sugar-containing foods.

 

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.