Taking Too Much Manganese

Manganese is a mineral that's nutritionally important to many metabolic processes that play a role in maintaining your brain health and bones, and healing wounds. A manganese deficiency is uncommon, but toxicity related to too much manganese exposure is a concern.

Manganese is an essential mineral you need in very small amounts. Your body contains about 10 to 20 milligrams of manganese, which is concentrated in the mitochondria of cells, primarily in the bones — 25 to 40 percent — and liver, brain, pancreas and kidneys, according to National Institutes of Health (NIH).

Your liver regulates the amount of manganese concentration in your tissues. More than 90 percent of absorbed manganese is excreted with bile into the feces, and a small amount is reabsorbed.

Manganese is a cofactor for several enzymes, including manganese superoxide dismutase, which acts as an antioxidant and helps neutralize free radicals that can damage the fats in your cellular membranes, according to University of Rochester. These manganese-activated enzymes play important roles in the metabolism of carbohydrates, cholesterol and amino acids.

Crucial for growth and development, manganese is required for bone formation, brain function and keeping your reproductive system functioning properly. Additionally, along with vitamin K, manganese plays a role in blood clotting and wound healing, says the NIH.

The NIH lists recommended amounts of manganese needed for good health. These values are set by the Food and Nutrition Board and vary by age and gender. Amounts include:

• Children ages 9 to 13 years: 1.9 milligrams
• Teens ages 14 to 18 years: 2.2 milligrams for males; 1.6 milligrams for females
• Adults ages 19 and older: 2.3 milligrams for males; 1.8 milligrams for females
• Pregnant and lactating women: 2 to 2.6 milligrams

You can usually get all the manganese you need from your diet. Many foods contain manganese, including seafood, whole grains, nuts, legumes, rice and leafy vegetables. Some of the top manganese-rich foods, according to the USDA, are:

• Mussels: 251 percent DV per 3 ounces
• Wheat germ: 246 percent DV per ounce
• Firm tofu: 129 percent DV per cup
• Sweet potatoes: 110 percent DV per cup
• Pine nuts: 109 percent DV per ounce
• Brown rice: 93 percent DV per cup
• Lima beans: 93 percent DV per cup
• Chickpeas: 73 percent DV per cup

Your body absorbs only about 1 to 5 percent of dietary manganese from food, according to the NIH. Foods high in oxalic acid, such as cabbage and sweet potatoes, or foods high in phytic acid, such as whole grains, beans and soy products, may slightly inhibit manganese absorption, according to the Linus Pauling Institute. Additionally tannins in tea may moderately limit retention of manganese, as may the intake of iron, calcium and phosphorus.

Manganese deficiency is very rare and hard to detect. Some medical conditions that restrict the absorption of minerals may cause you to have lower than normal levels of manganese in your body. According to the University of Rochester, symptoms of a deficiency may include:

• Slowed growth in children
• Abnormal glucose levels
• Changes in glucose tolerance
• Abnormal cholesterol levels
• Change in hair or beard color

If you cannot get the amount your body needs from manganese in food alone, single supplements are available in several forms, according to the Linus Pauling Institute. Some of these include:

• Manganese gluconate
• Manganese sulfate
• Manganese ascorbate
• Amino acid chelates of manganese

Of the supplements, manganese gluconate may be least likely to upset your stomach, according to the University of Rochester.

Manganese is often a component of multivitamin-mineral supplements or combination products, such as bone maintenance preparations. Most dietary manganese vitamin stand-alone supplements contain 5 to 20 milligrams of manganese, says the NIH.

Read more: Potential Benefits of Multivitamins

Although overdose from manganese is uncommon, certain condition may increase a susceptibility to manganese toxicity. Because of impaired liver function, people with chronic liver disease may not eliminate excess manganese efficiently. An accumulation of manganese in people with cirrhosis or liver failure may contribute to neurological problems, warns Linus Pauling Institute.

The brains of newborn babies may be more susceptible to manganese toxicity due to developing nerve cells and an immature liver; the liver is vital to manganese elimination. Compared to adults, infants and children have higher intestinal absorption of manganese with a lower ability to excrete the mineral, making them especially susceptible to detrimental neurotoxic effects.

In addition, a low level of iron may increase the risk of manganese accumulation in the brain.

Read more: Signs and Symptoms of Severe Iron Deficiency and Anemia

Taking too much manganese in the form of supplements can cause manganese side effects. According to the University of Rochester, symptoms of excess manganese may include:

• Loss of appetite
• Slowed growth
• Reproductive issues
• Anemia from manganese competing with iron for absorption

For people receiving intravenous feeding or for those with liver problems, serious toxicity may result from oral manganese supplements. Effects may include:

• Headache and insomnia
• Exaggerated tendon reflexes
• Memory loss
• Impaired motor skills
• Psychiatric issues
• Irreversible nerve damage that causes symptoms like Parkinson's disease
• Reproductive problems

Manganese is also a potent toxicant if you are exposed through inhalation of dust or fumes. This poisoning is a potential danger to individuals working in occupations such as mining or welding. Manganese toxicity may result in permanent neurological disorders, reports Linus Pauling Institute. Inhaled manganese is transported directly to the brain instead of first being metabolized by the liver.

Symptoms of this kind of toxicity can appear slowly, over a period of months to years. Manganese toxicity can start with symptoms such as:

• Psychiatric symptoms

• Irritability

• Aggressiveness

• Hallucinations

Progression to a more advanced form of toxicity, known as manganism, can cause neuromotor disorders similar to symptoms of Parkinson's disease, including:

• Tremors
• Difficulty walking
• Facial muscle spasms

Additionally, inhalation of manganese may cause an inflammatory response in the lungs, with side effects that include:

• Cough
• Acute bronchitis
• Decreased lung function

Manganese toxicity can also result from drinking water containing high levels of the mineral, such as well water. Linus Pauling Institute suggests that manganese in drinking water may be more bioavailable than manganese in food. However, evidence that manganese intake from drinking water could cause neurological symptoms, similar to those of Parkinson's disease, has been conflicting.

Children exposed to high levels of manganese in their drinking water may be affected in their cognitive abilities and behavior. Linus Pauling reported evidence that suggests these children had significantly lower scores on tests of intellectual function.