Manganese

What manganese is

Manganese is an essential trace element. It is a component of enzymes such as arginase, pyruvate carboxylase and manganese-dependent superoxide dismutase, which breaks down oxygen radicals in the mitochondria. Rich in manganese are nuts, tea leaves, legumes, whole grains and some fruits such as pineapple, bananas and berries; a cup of tea contains 300 to 1,000 micrograms. Dairy products, meat, fish and eggs contain little.

EFSA gives an adequate intake of 3 mg per day for adults, the D-A-CH societies 2 to 5 mg. In Germany, the median intake is 2.7 to 3.0 mg, in vegetarians 3.0 to 3.3 mg. In the BK-Score, human evidence stands at 3 out of 10 points: That manganese is indispensable is established; whether additional manganese does anything has barely been studied. The case is similar for other trace elements such as copper.

How it works

Only a small fraction of the manganese in food is absorbed, as a rule less than 10 percent. What reaches the blood is largely taken up by the liver and excreted again with the bile, so that only a little arrives in the circulation. In people with impaired liver and biliary function and under long-term intravenous feeding, manganese deposits in the brain have been described.

In excess, manganese accumulates in the basal ganglia, a brain region for the control of movement. The condition is called manganism and resembles Parkinson’s disease.

What the studies show

Depletion experiment: Friedman 1987

Seven men aged 19 to 22 ate a normal diet with 2.59 mg of manganese per day for 3 weeks, then a purified diet with 0.11 mg for 39 days. Plasma cholesterol fell from 170 to 152 mg/dl in the baseline phase and further to 142 mg/dl at the end of the depletion phase. Five of seven developed a transient skin change that disappeared when manganese was given again. The authors calculated the minimum requirement at 0.74 mg per day, and at 2.11 mg under unfavorable assumptions.

Bone: Strause 1994

In a double-blind, placebo-controlled study over 2 years, 59 healthy postmenopausal women, 66 years old on average, received placebo, trace elements alone (15 mg zinc, 5 mg manganese, 2.5 mg copper), calcium alone, or calcium plus trace elements. Bone density of the lumbar spine fell by 3.53 percent under placebo and rose by 1.48 percent under calcium plus trace elements; only this difference was significant. What share manganese had in this cannot be read from the study.

Safe level of intake: EFSA 2023

On behalf of the European Commission, EFSA systematically reviewed studies in humans and animals on nerve damage from manganese. The data were not sufficient to describe a dose-response relationship. Instead of an upper limit, EFSA therefore set a safe level of intake of 8 mg per day for adults, derived from the intake of people who take in particularly large amounts of manganese through normal foods. This does not determine the amount above which the risk rises.

Nerve damage: Stepens 2008

In Latvia, physicians examined 23 adults who had injected home-made methcathinone for years; in the production with potassium permanganate, manganese remained in the solution. All had gait disorders, 21 had quiet speech that was hard to understand. MRI showed changes in the basal ganglia, and manganese in the blood was elevated. The deficits did not regress after stopping. The intravenous route is not comparable with manganese from food, but the finding shows how sensitively the nervous system reacts.

Where the data stop

• Benefit of additional manganese. A controlled study with manganese as a single substance on bones, joints or metabolism does not exist in the sources reviewed.
• Who has a deficiency. In humans, a deficiency has only been described from one experiment with an extremely manganese-poor diet; a normal diet supplies roughly the recommended amount on average.
• Where the threshold for harm lies. EFSA could not determine it; the 8 mg per day is an amount with reasonable safety, not a threshold.

Status, approval and legal

Several manganese salts are authorized in the EU for the fortification of foods and for food supplements. The BfR recommends no more than 0.5 mg of manganese per recommended daily dose for food supplements and advises against fortifying normal foods with manganese. It derived the value from a British guidance value for older people; the BfR has announced an adjustment to the 2023 EFSA assessment. The BfR values are recommendations, not legal provisions.

For manganese, the EU has authorized four health claims: energy metabolism, bones, connective tissue and protection of cells from oxidative stress.

Safety

The central risk is nerve damage. It is known mainly after inhaling manganese in mining and welding. Through diet, EFSA describes, among other things, an individual case with around 26 mg of manganese per day from about 3 liters of black tea over more than 10 years; after chelation therapy, most symptoms improved.

Because there is little distance between the usual intake and the amounts at which effects have been observed, the BfR considers only 0.5 mg in supplements acceptable; this leaves no room for a second manganese-containing product. In the BK-Score, safety stands at 5 out of 10 points; this axis measures how well safety has been studied, not how safe the substance is. This text is information and does not replace medical advice.

Sources

• EFSA NDA Panel, EFSA Journal 2023 – Tolerable upper intake level for manganese, safe level of intake 8 mg per day
• BfR – Proposed maximum levels for manganese in foods including food supplements (2021)
• Friedman BJ et al., J Nutr 1987 – depletion study, 7 young men, 39 days
• Strause L et al., J Nutr 1994 – placebo-controlled study, 59 postmenopausal women, calcium and trace elements over 2 years
• Stepens A et al., N Engl J Med 2008 – parkinsonian syndrome in 23 methcathinone users and the role of manganese
• Regulation (EU) No 432/2012 – list of permitted health claims made on foods