Dietary standards for manganese: overlap between nutritional and toxicological studies.

The Estimated Safe and Adequate Daily Dietary Intake (ESADDI) for adults for manganese is 2-5 mg Mn/d. The LOAEL (lowest-observable-adverse-effect level) for manganese in water is 0.06 mg Mn/(kg.d) or 4.2 mg Mn/d for a 70-kg individual. The inconsistency in these standards reflects limitations in the available data as well as differences in the way in which the standards are calculated. Manganese balance and excretion data are not useful biomarkers of manganese exposure but do demonstrate that the body is protected against manganese toxicity primarily by low absorption and/or rapid presystemic elimination of manganese by the liver. Serum manganese concentrations in combination with lymphocyte manganese-dependent superoxide dismutase (MnSOD) activity, and perhaps blood arginase activity, seem to be the best way to monitor ingestion of insufficient manganese. Serum manganese concentrations in combination with brain magnetic resonance imaging (MRI) scans, and perhaps a battery of neurofunctional tests, seem to be the best way to monitor excessive exposure to manganese.