Manganese is an essential trace element that is involved in our metabolism, is required for the production of many important enzymes, and is also involved in the synthesis of an important antioxidant for our body. (1) Its deficiency is very rare, as most foods contain small amounts of it, making its supplementation unnecessary. (1) Some research suggests that manganese deficiency may impair blood sugar levels and bone health, and may play a role in the development of many other diseases. (2) However, few human studies have been done on its health effects.

How to ensure the required intake of manganese?

The required intake has been officially set at 1.8-2.5 mg per day, while a slightly higher intake of 2.6-3 mg is recommended for pregnant and breastfeeding women. (3,4) The average intake of manganese is higher than this, so there is no need to worry about deficiency with a balanced diet.

The best sources of manganese are cereals, pulses, seafood, vegetables, but coffee and tea, and even spices, are rich in manganese. (3) Even if shellfish isn't consumed the world over, cereals, vegetables, and coffee are almost universally consumed, so manganese deficiencies rarely arise.

Manganese is also available in the form of dietary supplements and many multivitamins contain it, but given that its intake is essentially adequate for everyone, it is only worth supplementing in cases of confirmed deficiency.

The absorption of manganese from both food and supplements is very low: on average, less than 5% of the amount consumed is absorbed (5).

What happens in case of a deficiency or an overdose?

Manganese deficiency is so rare that it has so far only been experimentally induced in humans. It can lead to impaired blood sugar control, weak bones, and birth defects (6).

However, manganese, like many other trace elements, can be overdosed, although this is almost impossible through improper diet. It usually occurs in people whose work environment causes them to inhale too much manganese. (9) Over time, manganese overdose causes neurological damage and, like its deficiency, negatively affects blood sugar regulation. (2,9)

The interrelation of manganese and iron

Manganese absorption is very low by design but may decrease further depending on iron supply. Higher levels of ferritin, a form of stored iron, mean that much less manganese is absorbed from our food. Ferritin levels influence manganese absorption so greatly that they are more central to regulating manganese supply than the intake of manganese itself. (10)

The health effects of manganese

Manganese is needed to produce many enzymes that play an important role in blood sugar regulation. Consequently, manganese intake has an impact on the risk of type 2 diabetes, with too much manganese bearing an equally negative effect. Based on observational studies, a U-shaped curve has been observed to describe the relationship between manganese intake and risk of diabetes, meaning that deficiency and excess intake have similarly adverse effects (11).

Manganese-dependent superoxide dismutase is an important antioxidant that forms a part of our body's antioxidant system. Along with vitamin C, vitamin E, and other antioxidants, it protects us from damage caused by free radicals arising from our environment and our metabolism. (12) This manganese-dependent antioxidant protects primarily the energy-producing parts of our cells from damage, but, as has been shown for many other antioxidants, excess intake has an inverse effect and increases oxidative stress.

Although manganese is likely to affect the risk of developing various diseases, there are currently no good quality human studies to draw firm conclusions about the relationship between manganese intake and the risk of various diseases. Manganese supplementation has been shown to have a beneficial effect in some studies, but unfortunately in almost all cases, it has been supplemented alongside substances that by themselves improve the given problems.