Manganese in pregnancy: evidence and safety

How does manganese work?

Manganese works as a cofactor for many enzymes, among them manganese superoxide dismutase, arginase, and pyruvate carboxylase. Through those it takes part in amino acid, cholesterol, glucose, and carbohydrate metabolism, reactive oxygen species scavenging, bone formation, reproduction, and immune response, and it has a role in blood clotting and hemostasis alongside vitamin K. The body bounds the supply tightly at both ends: only about 1 to 5 percent of dietary manganese is absorbed, through an active transport system in the small intestine and possibly by diffusion when intake runs high, and more than 90 percent of what is absorbed leaves through bile into the feces. That homeostatic control is the backdrop to the Institute of Medicine's conclusion that manganese supplements are not indicated during pregnancy.

What does the evidence say about manganese in pregnancy?

• The adequate intake is 2.0 mg a day during pregnancy and 2.6 mg during lactation for women 19 to 50, against a tolerable upper intake level of 11 mg for adults 19 and older. Grain products, tea, and vegetables supply most of it in typical American diets. 1
• Among 1,033 pregnant women followed prospectively, those who delivered preterm averaged 3.60 mg of dietary manganese a day versus 2.99 mg in those who delivered at term (P = .03), with an odds ratio of 1.12 (95 percent CI 1.02 to 1.23). Seven percent of the cohort delivered preterm. 2
• Manganese toxicity acts mainly on the central nervous system, producing tremor, muscle spasms, rigidity, and neuromotor problems that resemble Parkinson disease. Documented cases came from drinking water carrying manganese as high as 28 mg/L. 1
• The Institute of Medicine concluded that manganese supplements are not indicated during pregnancy, noting that the body maintains strong homeostatic control and that deficiency has never been observed in pregnant women, who typically consume around 2 mg a day already. 3
• A 2021 review proposing an optimal prenatal formula suggested 1 mg of manganese daily against an 11 mg upper limit, while flagging that cord blood manganese above the 75th percentile was negatively associated with neurodevelopment scores and that more research is needed. 4

What's on the label?

Labels carry manganese either as an amino acid chelate (manganese bisglycinate chelate, manganese glycinate chelate, manganese aspartate) or as the gluconate, picolinate, sulfate, citrate, or chloride salt. The amounts split sharply by product type: NIH ODS puts multivitamin and mineral products at 1.0 to 4.5 mg and standalone manganese supplements at 5 to 20 mg. Read that second range against the 2.0 mg pregnancy adequate intake and the 11 mg adult upper limit before stacking one on top of a prenatal.

What should I know before taking manganese?

Please consult your healthcare provider before adding this supplement to a prenatal regimen, particularly if you are on prescription medication or have a scheduled procedure. Supplement contents are not FDA-verified, so a labeled dose and an actual dose can differ; look for third-party-tested brands.