Manganese supply in everyday life — figures, sources, limits

Where the trace element in our food comes from

Manganese enters plants through the roots and from there reaches the plate. The content of a food therefore depends greatly on what it grew in and which part of the plant is eaten. Outer layers and germs of cereals contain considerably more than the milled interior of the flour, which is why wholegrain products rank high in every content table.

Animal foods supply comparatively little. Meat, fish, milk and eggs are mostly in the range of hundredths of a milligram per hundred grams. A household's manganese intake therefore depends almost entirely on the plant side of the menu.

Why wholegrain and nuts rank so highly

In the aleurone layer of the cereal grain, minerals are stored in bound form, mostly as salts of phytic acid. When milled into white flour, most of this fraction is lost. Nuts and oilseeds, in turn, are in a sense concentrated germs and accordingly bring high contents with them.

Rounded orientation values from common nutrition tables. The reference value is 2 mg per day under Annex XIII of Regulation (EU) No 1169/2011.

Tea as an unusual but productive source

Dried tea leaves are among the most manganese-rich plant materials of all. When infused, part of it passes into the drink, so that a cup of black or green tea makes a measurable contribution to daily intake depending on steeping time. In population groups with high tea consumption, tea is arithmetically one of the three largest sources.

What actually happens in connective tissue

Connective tissue does not only connect; it carries, cushions, conducts and stores water. Its mechanical properties arise from the interplay of fibres and ground substance. The fibres provide tensile strength, the ground substance compressive elasticity. Both components are produced by cells, which employ a whole series of enzymes for the purpose.

Manganese as a cofactor of the glycosyltransferases

Proteoglycans are proteins to which long sugar chains are attached. Glycosyltransferases perform this linking, and many of them need a divalent metal ion to position the sugar substrate correctly. Manganese is among the ions that can fill this position. This is precisely where the authorised claim on connective tissue formation is derived from.

Under Regulation (EU) No 432/2012

Manganese superoxide dismutase in the mitochondria

MnSOD is one of the few enzymes whose name already contains the bound metal. It works in the mitochondrial matrix and converts superoxide radicals into hydrogen peroxide, which is then processed further by catalase and glutathione peroxidase. Without this first step, superoxide would react with the iron-sulfur centres of the respiratory chain.

Under Regulation (EU) No 432/2012

Reference values, intake and upper limits

For manganese there is no derived requirement value in the strict sense, because the data is not sufficient to derive one. Professional bodies therefore work with estimated values for an adequate intake. On food packaging, by contrast, the uniform EU reference value of 2 mg appears, against which the percentages are calculated.

The values serve as orientation and do not replace individual dietary advice.

Phytate, iron and the competition for the same transport route

The content of a food and the amount actually absorbed are two different quantities. From a mixed diet, only an estimated few percent of the manganese contained is absorbed. Phytic acid from cereals and pulses binds the ion and lowers uptake — in precisely those foods that show the highest contents. Iron and manganese also partly use the same transporter in the intestinal mucosa, which is why a very high iron intake arithmetically lowers manganese uptake.

Soaking, sprouting and long dough fermentation break down part of the phytate. That is why slowly fermented sourdough bread performs better in bioavailability studies than quickly baked wholemeal bread with an identical content.

What the body does with the excess

Absorbed manganese is released predominantly via the liver into the bile and excreted in the stool. This route is the essential regulatory mechanism. That is why blood values alone are rarely informative, and why excessive exposure in the specialist literature mainly concerns situations in which uptake bypasses the intestine — for example with parenteral nutrition or occupational dust exposure.

Four authorised claims, considered individually

The following overview reproduces the authorised wording. Each claim stands on its own and applies to manganese alone. Combining several claims into one sentence would not be legally permissible.

The condition behind every claim

An authorised claim may not be used arbitrarily. It presupposes that the food in question contains at least a significant amount of the nutrient — for most products that is 15 % of the reference value per 100 g, i.e. 0.3 mg of manganese. Only then is the claim permissible, and even then only in the exact wording or in an equivalent formulation that does not take the consumer further than the original.

What such a claim expressly does not say: that a higher intake would have an additional effect, that a set of symptoms would change as a result, or that a product would be equivalent to a medical intervention.

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