The image reflects the origin of name of the element in the form of an antique electro magnet .

Manganese is an essential trace nutrient in all known living organisms.  Many classes of enzymes have manganese cofactors.  Manganese is also important in photosynthesis in plants as the metalloenzyme core of the oxygen-evolving complex contains four atoms of manganese. Certain soils are deficient in manganese and so it is added to some fertilisers and given as a food supplement to grazing animals.  The average human body contains about 12 milligrams and we take in about 4 milligrams per day from such foods as nuts, bran, wholegrain cereals, tea and parsley.  Without it, bones grow spongier and break more easily.  Manganese may also be essential for utilisation of vitamin B. 

Skin Integrity

Manganese is a required co-factor for an enzyme called prolidase, which is in turn necessary to make collagen as a structural component of skin. It is also a co-factor for an enzyme called manganese superoxide dismutase (MnSOD), which is a potent antioxidant associated with protection against UV damage.

When human volunteers eat a manganese-depleted diet for several weeks, they develop a reversible red and itchy skin rash. Given that MnSOD activity declined markedly during the low manganese diet, it is likely that this enzyme played a key role in this rash.

Blood Sugar Control

Manganese is needed to help multiple enzymes in a process called gluconeogenesis. This is the process by which we build non-carbohydrate food products—for example, digested fats—into sugars to burn as fuel.

In animal studies, manganese-depleted diets can lead to high blood sugars similar to those seen in diabetics. Whether this is true in humans has not been determined.

Either way, manganese deficiency is probably not a common contributor to human diabetes. Humans with diabetes do not reliably have lower manganese intake than people without diabetes. Also, supplementation with large doses of manganese—doses at the top end of what would be seen with plant-based diets—did not improve blood sugar control in diabetes.

Protection Against Free Radical Damage

As noted above, manganese is a co-factor for an enzyme called manganese superoxide dismutase (MnSOD), which is a potent antioxidant associated with protection against free radical damage. Diets low in manganese have been linked to conditions marked by increased oxidative stress, including skin problems and asthma.