What is a safe daily intake for manganese?
For most healthy adults (19 years and older), manganese is considered likely safe when consumed orally in amounts up to 11 mg daily. This 11 mg figure is the Tolerable Upper Intake Level (UL) established by the National Academies of Sciences, Engineering, and Medicine, representing the maximum daily intake unlikely to cause harmful health effects. The Adequate Intake (AI) for adult men is 2.3 mg per day, and for adult women is 1.8 mg per day. In contrast to dietary intake, manganese from supplements and contaminated water can pose a higher risk of toxicity, as it is more readily absorbed by the body.
Tolerable Upper Intake Levels (UL) for manganese
The UL for manganese varies significantly by age. It is crucial to adhere to these guidelines to prevent adverse effects.
- Adults (19+ years): 11 mg/day
- Pregnant and breastfeeding women (19+ years): 11 mg/day
- Adolescents (14–18 years): 9 mg/day
- Pregnant and breastfeeding adolescents (14–18 years): 9 mg/day
- Children (9–13 years): 6 mg/day
- Children (4–8 years): 3 mg/day
- Children (1–3 years): 2 mg/day
- Infants (0–12 months): UL not determined; intake should only be from food and formula.
Sources of manganese: Diet vs. supplements
Most people can obtain sufficient manganese from their diet alone, and deficiency is uncommon. A balanced, varied diet rich in plant-based foods typically provides all the manganese required. Manganese is found in many common foods, including whole grains, nuts, legumes, leafy vegetables, and tea.
However, some factors can inhibit dietary manganese absorption, such as high intake of phytates (found in nuts, seeds, and whole grains) or oxalates (in spinach and sweet potatoes). In contrast, manganese in supplements is often more bioavailable and absorbed more efficiently by the body. While this can be beneficial for those with documented deficiencies, it also increases the risk of reaching toxic levels, especially with long-term use at high doses.
Comparing manganese to other trace minerals
| Feature | Manganese (Mn) | Iron (Fe) | Zinc (Zn) |
|---|---|---|---|
| Function | Essential for metabolism, bone health, antioxidant defense (MnSOD), and enzyme activation. | Crucial for hemoglobin formation, oxygen transport, and cell growth. | Important for immune function, wound healing, and DNA synthesis. |
| Sources | Whole grains, nuts, legumes, leafy greens, tea. | Red meat, poultry, beans, spinach, fortified cereals. | Oysters, red meat, poultry, beans, nuts, dairy products. |
| Absorption Interaction | Competes with iron and calcium for absorption, and absorption is increased during iron deficiency. | Influences manganese absorption; low iron stores increase Mn absorption. | Can compete with manganese for absorption at very high doses. |
| Toxicity Risk | Primarily from inhalation or excessive supplementation; buildup is regulated by the liver and excretion via bile. | High doses from supplements can cause gastrointestinal distress and, in severe cases, liver damage. | Chronic high intake can interfere with copper absorption and cause anemia. |
Side effects and toxicity from excessive intake
Excessive manganese intake, particularly from supplements or occupational exposure to manganese dust, can lead to serious health issues. The body tightly regulates manganese absorption and excretion, but this system can be overwhelmed by high intakes.
Manganism: The primary risk
Perhaps the most well-known consequence of manganese toxicity is a neurodegenerative disorder called manganism, which presents symptoms similar to Parkinson's disease. Early symptoms can include irritability, mood changes, and compulsive behaviors, followed by motor symptoms like tremors, difficulty walking, and muscle spasms. Inhaled manganese is particularly dangerous as it bypasses normal metabolic controls in the liver and goes directly to the brain.
Who should be cautious with manganese supplements?
Certain individuals are at a higher risk for manganese toxicity and should avoid or limit supplementation, consulting a healthcare provider before use.
- Individuals with chronic liver disease: People with liver problems have a reduced ability to excrete manganese through bile, which can lead to a dangerous buildup in the body.
- People with iron-deficiency anemia: Those with low iron levels tend to absorb more manganese, increasing their risk of toxicity if excess is present.
- Infants and children: Young children have higher intestinal absorption and lower excretion rates of manganese, making them more vulnerable to its neurotoxic effects. The UL for children is significantly lower than for adults.
- Welders and miners: Occupational exposure to inhaled manganese dust is a significant risk factor for manganism.
- Individuals with certain medical conditions: Patients on total parenteral nutrition (TPN) and those with specific genetic predispositions may also have an increased risk.
Conclusion: Prioritize dietary intake and consult a professional
Yes, you can take manganese every day, but for most people, it should come from dietary sources and not from supplements. Maintaining a balanced diet rich in whole grains, nuts, and leafy greens is generally sufficient to meet the body's needs and prevent deficiency, which is rare. The key is to stay within the recommended Adequate Intake (AI) and well below the Tolerable Upper Intake Level (UL) of 11 mg per day for adults. The risks associated with excessive manganese intake, particularly for those with underlying health conditions or occupational exposure, far outweigh any perceived benefits of high-dose supplementation. Always consult a healthcare provider before beginning any supplement regimen, especially if you have liver disease, iron deficiency, or are considering long-term use.
Is it safe to take manganese every day?
It is generally safe for healthy adults to consume manganese daily, provided the intake is from food and does not exceed the Tolerable Upper Intake Level (UL) of 11 mg. For most people, dietary intake is sufficient, and supplements are not necessary.
What is the highest safe daily dose of manganese?
The Tolerable Upper Intake Level (UL) for adults 19 years and older is 11 mg of total intake per day from food, water, and supplements. Taking more than this amount, especially from supplements over a long period, is possibly unsafe and increases the risk of side effects.
How can I get enough manganese from my diet?
Good dietary sources of manganese include whole grains (brown rice, oatmeal), nuts (pecans, hazelnuts), legumes (chickpeas, lentils), leafy greens (spinach, kale), and tea. A balanced diet typically provides the adequate amount, and deficiency is rare.
What are the symptoms of manganese toxicity?
Symptoms of manganese toxicity, or manganism, can include neurological issues similar to Parkinson's disease, such as tremors, difficulty walking, and facial muscle spasms. Other symptoms may include irritability, memory loss, headaches, and other central nervous system effects.
Can manganese supplements cause side effects?
Yes, taking high-dose manganese supplements long-term can lead to muscle pain, nerve damage, and psychiatric symptoms like fatigue and depression. The risk is higher for those with liver disease or iron deficiency.
Does dietary manganese have the same risks as inhaled manganese?
No, inhaled manganese (from occupational exposure like welding) is more directly toxic to the central nervous system because it bypasses the liver's normal metabolic controls. While excessive dietary intake can also be toxic, the risk profile and severity are different.
Are there any drug interactions with manganese supplements?
Yes, manganese can interact with certain medications. For example, it can bind to tetracycline and quinolone antibiotics in the stomach, reducing their effectiveness. It is recommended to take manganese supplements at least one to four hours apart from these drugs.
Who should not take manganese supplements?
Individuals with liver disease, iron-deficiency anemia, and infants and children are especially vulnerable to manganese toxicity and should be cautious or avoid supplementation entirely unless directed by a doctor. Occupational exposure should also be monitored.
What is manganism?
Manganism is a severe and progressive neurodegenerative disorder resulting from excessive manganese exposure, often presenting with motor dysfunction and psychiatric symptoms that resemble Parkinson's disease. In advanced cases, the neurological damage can be permanent.
