Doses at 1, 5 or 10 mg manganese in food supplements may increase risk for irreversible neurotoxic adverse effects.
This is the conclusion from the Norwegian Scientific Committee on Food and Environment (VKM) in an assessment of dietary intake of manganese in relation to tolerable upper intake level.
VKM has evaluated doses at 1, 5 and 10 mg manganese per day. The previous maximum limit for manganese in food supplements was 5 mg.
Irreversible neurotoxic adverse effects from intakes of manganese close to adequate intakes have been reported in humans. A no observed adverse effect level (NOAEL) could not be set, because all the doses tested reported negative effects. Consequently, no tolerable upper intake level (UL) could be established for manganese.
Manganese is an essential mineral in humans. Norwegian authorities have not suggested any recommendations for intake of manganese. In 2013, the European Food Safety Authority (EFSA) suggested 3 mg/day to represent an adequate intake (AI) of manganese.
Main contributor to dietary manganese intake is cereals (57%) followed by fruit, vegetables, nuts and coffee/tea. In Norway, manganese content in drinking water is low.
Daily dietary intake of manganese in Norway is not known, but it is proposed that manganese intake is adequate in the Scandinavian countries. EFSA report on an observed mean intake in EU around 3 mg/day for adults.