Daily manganese requirements and the safe upper limit

Short answer: The NIH Office of Dietary Supplements sets the Adequate Intake for manganese at 2.3 mg per day for adult men and 1.8 mg per day for adult women. Most people reach these levels through a varied diet, and the Tolerable Upper Intake Level for adults is 11 mg per day from all sources combined.

What is manganese and why does the body need it?

Manganese is an essential trace mineral found naturally in many foods. According to the NIH Office of Dietary Supplements, it serves as a cofactor for several key enzymes, including manganese superoxide dismutase, arginase, and pyruvate carboxylase. Through these enzymes, manganese is involved in amino acid, cholesterol, glucose, and carbohydrate metabolism. It also contributes to the body's antioxidant defense system by helping scavenge reactive oxygen species.

Research also supports a role for manganese as a cofactor for enzymes involved in bone formation. The evidence that manganese performs these physiological functions is graded as strong by the NIH. However, it is important to note that supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA.

Daily targets: Adequate Intake, not an RDA

Unlike many nutrients, manganese does not have a Recommended Dietary Allowance (RDA). Instead, the Food and Nutrition Board established an Adequate Intake (AI), which is used when there is not yet enough data to set a precise RDA. The NIH Office of Dietary Supplements reports the following AI values for adults aged 19 and older:

• Men (19 years and older): 2.3 mg per day
• Women (19 years and older): 1.8 mg per day

These figures represent estimated intakes assumed to meet the needs of most healthy adults. Because they are AIs rather than RDAs, they carry a slightly higher degree of uncertainty. If you are unsure whether your intake is appropriate for your individual circumstances, speak with a clinician or registered dietitian.

The Tolerable Upper Intake Level: 11 mg per day

The Food and Nutrition Board set the Tolerable Upper Intake Level (UL) for manganese at 11 mg per day for all adults aged 19 and older. This figure applies to intake from all sources combined, meaning food, water, and supplements together.

The UL was established based on evidence linking whole-blood manganese concentrations above the normal range with a risk of neurotoxicity. Exceeding the UL consistently may therefore pose a safety concern for otherwise healthy adults. That said, the NIH notes there is no evidence of toxicity from high dietary intakes alone. The concern arises primarily with supplemental or occupational exposure.

One important clarification from the NIH: the UL does not apply to individuals taking supplemental manganese under medical supervision. If a clinician has recommended a specific supplemental dose for a clinical reason, that guidance takes precedence over the general population UL.

What does the research actually show?

It is worth being transparent about the strength of evidence behind various claims you may encounter about manganese. Here is how the NIH grades the key areas:

• Enzyme cofactor and metabolic roles: Strong evidence supports manganese's function as a cofactor for manganese superoxide dismutase, arginase, and pyruvate carboxylase, and its involvement in normal metabolism.
• Bone formation: Strong evidence supports manganese's role as a cofactor for bone-related enzymes. However, evidence that manganese supplementation improves bone mineral density or reduces osteoporosis risk in humans is graded as insufficient.
• Type 2 diabetes: Evidence that manganese status is associated with, or affects the risk of, type 2 diabetes is graded as insufficient.
• Deficiency: Evidence that manganese deficiency causes defined clinical signs in humans is graded as limited.

In plain terms, the physiological roles are well established, but the clinical benefits of supplementation beyond meeting the AI are not yet supported by strong human evidence in most areas.

Food sources

Most adults in countries with varied diets meet the AI through food alone. Rich dietary sources include whole grains, legumes, nuts, seeds, leafy green vegetables, and tea. Because manganese is widespread in plant foods, people who eat a balanced diet are unlikely to fall short of the AI.

Absorption and nutrient interactions

The NIH Office of Dietary Supplements notes that manganese is not known to have any clinically relevant interactions with medications. If you take any prescription or over-the-counter medications alongside supplements, talk to your doctor or pharmacist before combining them, as individual circumstances vary.

There is, however, a notable interaction between manganese and iron. Iron and manganese appear to share an intestinal transporter, which can lead to competitive absorption. Dietary iron intake and iron status, measured by serum ferritin, are inversely associated with manganese absorption. In practical terms, low iron status increases manganese absorption and may increase the risk of manganese accumulating to higher levels. People with iron deficiency should be aware of this relationship, particularly if they are also taking manganese supplements.

Who should pay closer attention?

For the general healthy adult population, manganese intake from food alone is unlikely to approach the 11 mg UL. Concerns about exceeding the UL are more relevant for people who:

• Take multiple supplements that each contain manganese
• Use high-dose or combination supplement products without reviewing total manganese content
• Have low iron status, which can increase manganese absorption
• Have been advised by a clinician to monitor their trace mineral intake

A note on personal dosing

The figures in this guide are population reference values published by the NIH Office of Dietary Supplements and the Food and Nutrition Board. They are not personal medical advice. Your individual needs may differ based on health status, diet, medications, and other factors. Always consult a clinician or pharmacist before starting a new supplement, adjusting your dose, or combining supplements with other treatments.

Sources

• NIH Office of Dietary Supplements, Manganese Health Professional Fact Sheet: https://ods.od.nih.gov/factsheets/Manganese-HealthProfessional/
• NIH Office of Dietary Supplements, Manganese Consumer Fact Sheet: https://ods.od.nih.gov/factsheets/Manganese-Consumer/
• National Academies of Sciences, Dietary Reference Intakes: https://nap.nationalacademies.org/catalog/10026