Manganese is a naturally occurring essential nutrient required to maintain the normal physiological functioning in humans, animals and plants. Naturally ubiquitous in the environment, manganese can be found in rocks, soils, rivers, underground waters and foods such nuts, legumes, seeds, tea, whole grains, and leafy green vegetables, to name but a few.
Manganese deficiency has not been reported in humans. However, lack of manganese in animals has been found to cause improper formation of bone and cartilage and in soils with reduced manganese content usually due to poor drainage, crops sown on these soils suffer from yellowing of leaves, brown spots and severely affected leaves wither.
Excess manganese in the environment can cause health effects in humans and animals but excess conditions in plants/crops are rare.