Required in trace amounts, this metal can wreak havoc in the body in excess. Too much manganese triggers oxidative stress, inflammation, as well as cognitive and reproductive issues. It can make infections more dangerous and lead to a Parkinson’s-like condition called manganism. Read on to find out more about manganese toxicity and ways to combat it.
What is Manganese?
Multiple enzymes require manganese as a cofactor. These enzymes play roles in:
- Energy (ATP) production in the mitochondria 
- Antioxidant defense (including superoxide dismutase) 
- Burning fats, proteins, and sugars [1, 2]
- Brain development and health 
- Immune response 
- Sex hormone production and reproductive health [2, 7]
- Digestion 
- Building bones and connective tissue [2, 7]
Traces of manganese are part of a healthy diet. However, exposure to excess levels can be toxic .
Because it’s found pretty much everywhere, you’re more likely to have excess manganese than to be deficient.
Absorption & Elimination
You get most manganese through your diet .
Of the manganese you take in, only 1 – 5% is absorbed into the blood. This level is tightly regulated based on the amount of Mn in your diet. You will absorb less if you’re eating a lot of manganese-rich food .
Excess manganese is transported to the liver and released into the bile, which is passed back into the gut and removed with the stool. About 80% of manganese is eliminated this way, while small amounts can also be removed with urine, sweat, and breast milk [8, 11].
Manganese in mostly stored in the bones (40%), liver, kidneys, pancreas, and adrenal and pituitary glands. Some are dispersed in your bloodstream and can readily travel across the blood-brain and placental barriers [11, 8].
You can check your brain levels with an MRI. But it is only good for recent exposures, spanning a few months .
Symptoms of Manganese Toxicity
- Eye issues
- Sore throat
- Memory loss
- Hand tremors
- Exaggerated reflexes
- Muscle cramps
Aside from the above symptoms, too much manganese can cause a long list of side effects. These mainly depend on the amount and duration of exposure.
Side Effects of Too Much Manganese
1) Causes Manganism (Manganese Toxicity)
Next, issues with short-term memory and computational ability follow .
Symptoms of early poisoning stages are reversible .
At a point, manganese toxicity becomes irreversible. It starts to damage the brain, and a horrifying sequence follows: the damage progresses, even without further exposure. Symptoms include a loss of balance, uncontrollable tremors (dystonia), slow and clumsy movements (bradykinesia), face muscle spasms, speech disturbance, rigidity, and gait abnormalities [22, 8, 23, 11].
Many symptoms of manganism resemble those of Parkinson’s disease. However, manganism targets different brain regions (globus pallidus and striatum as opposed to substantia nigra). It is also doesn’t improve with levodopa, unlike Parkinson’s [23, 5].
2) Increased Oxidative Stress
Trace amounts of manganese help your body fight oxidative stress, but too much of this metal actually makes it worse.
In excess, manganese builds up in mitochondria and increases the production of reactive oxygen species (ROS). It also depletes the antioxidant glutathione, according to rat and monkey studies [20, 23, 4].
3) Triggers Inflammation
Excess manganese triggers the release of several inflammatory molecules (including TNF-α, IL-6, IL-1β, prostaglandins, and nitric oxide). It also activates the body’s key inflammatory signal, NF-κB. Altogether, this can cause inflammation in the brain and body [4, 24, 23].
4) Impairs Cognition (Lowers IQ)
In addition, a review of 21 studies concluded manganese in drinking water worsens cognitive function in school-aged children .
Children who are exposed to higher Mn perform more poorly in school, measured by mastery of language, mathematics, and overall grade average:
- In 2 studies conducted in Canada with 630 children, higher Mn levels in drinking water were associated with lower IQ scores .
- In a study of 201 school children in Bangladesh, higher drinking water Mn was associated with lower achievement scores in mathematics .
- Among 172 children in Mexico, those exposed to more airborne Mn performed worse on cognitive function tests .
- In another group of 265 Mexican children, higher Mn hair levels were linked with decreased verbal memory and learning .
- Similarly, in another 2 studies of 83 Brazilian children and 106 US children, higher Mn hair levels were associated with poorer cognitive function and lower IQ [32, 33].
Long-term exposure to high levels of manganese can also cause mild cognitive impairment in adults .
In 95 workers, those exposed to more Mn-containing welding fume had poorer working memory .
Further, in a study of 60 Chinese workers, higher bone and fingernail but not blood manganese was linked to worse cognitive function .
5) May Increase ADHD Risk
In a meta-analysis of 4 studies with 175 ADHD and 999 healthy children, children with ADHD had higher manganese levels .
In addition, in a study of 288 adults living in a mining district in Mexico, those exposed to higher air Mn levels were at a higher risk of having attention problems .
6) Damages the Brain
In a study of 66 people, welders chronically exposed to manganese had smaller brain areas (globus pallidus, cerebellum) compared to unexposed people. Those with larger reductions had more cognitive and behavioral symptoms .
7) May Contribute to Anxiety
In one study of 101 people, patients suffering from generalized anxiety had elevated Mn levels .
8) May Contribute to Parkinson’s
It is possible that the elderly have a propensity for Parkinson’s that could be “pushed over the edge” by increased doses of manganese .
Also, chronic exposure to high Mn levels may accelerate Parkinson’s disease by lowering dopamine and promoting protein clumping in the brain (alpha-synuclein protein misfolding) .
In a meta-analysis of 22 studies with over 2k patients with Parkinson’s and as many healthy controls, those with Parkison’s had higher Mn blood levels .
9) May Contribute to Alzheimer’s
High manganese may be involved in Alzheimer’s by increasing blood amyloid-beta levels.
Amyloid beta creates plaques in the brain linked to cognitive impairment in Alzheimer’s. Chronic Mn treatment in monkeys increased these brain plaques. Additionally, advanced stages of manganese poisoning have been linked to dementia [48, 49, 50].
10) May Contribute to ALS
One study found higher Mn levels in the spinal cord of 7 ASL patients compared to 6 controls .
In addition, ALS is common in patients with liver cirrhosis, a condition in which manganese builds up since bile flow is impaired .
11) Disrupts Sex Hormones
An observational study conducted among factory workers in the ’80s showed that Mn-exposed male workers had significantly fewer children than those not exposed to Mn, suggesting this metal may decrease fertility .
More recently, in a study of 84 male workers exposed to Mn and 92 controls, those exposed to manganese had lower testosterone and higher gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) levels. They also had decreased sperm motility .
Several studies have found higher prolactin levels in Mn-exposed workers (251 and 179 welders) and children living in Mn-rich zones (77 and 225 children). High prolactin levels can cause reproductive problems in both men and women [54, 55, 56, 57].
Manganese can trigger the early onset of puberty (by stimulating the hypothalamic-pituitary axis). Exposure to Mn induces early puberty in rats, raising sex hormones such as estradiol [58, 59, 60, 61].
12) May Impair Sleep
In a study of 15 people, chronic Mn intoxication decreased REM sleep .
13) Makes Microbes More Dangerous
In mice, a high-Mn diet promotes S. aureus, a common cause of skin and respiratory infections, sinusitis, and food poisoning .
14) May Worsen Prion Disease
Animals and humans with prion disease have increased Mn levels in blood, brain, and liver .
However, to date, there is no evidence to say Mn overload causes prion disease .
15) May Damage the Heart
16) Can Blunt the Sense of Smell
In a study of 60 people, those exposed to airborne Mn had an impaired sense of smell .
17) May Cause Asthma
Mn belongs to the group of “transitional metals” – known inducers of occupational asthma. Nevertheless, only a single case of Mn-induced asthma has been well-documented so far .
18) Increases Infant Mortality
High manganese levels in water have been linked to increased infant mortality .
Across North Carolina (population over 8 million), the increase in groundwater Mn was associated with a higher rate of county-level infant deaths .
In a study of over 26,000 babies in Bangladesh, infants exposed to higher water Mn were more likely to die during the first year of life .
19) May Increase Cancer and Liver Disease Mortality
In an observational study of 14 Chinese towns and 28 villages, the concentration of Mn in drinking water was associated with higher cancer rates and deaths .
Similarly, high drinking water but not airborne Mn levels were associated with higher cancer mortality in the state of North Carolina .
On the other hand, higher airborne levels of on-road Mn were linked with higher chronic liver disease deaths in North Carolina .
Who is at Risk of Manganese Toxicity?
1) Infants and Children
Children also accumulate more manganese in the brain, since their blood-brain barrier is more permeable. In addition, their bile excretion capacity is lower .
Therefore, children may easily exceed the recommended dietary intake of manganese through a combination of airborne and dietary sources .
The 2011-2012 National Health and Nutrition Examination Survey (NHANES) found higher Mn levels in children, the highest ones being in 1-year-olds .
Cow milk-based and soy-based infant formulas are higher in Mn than human breast milk.
That’s why formula-fed infants have higher Mn levels than in their breast milk-fed counterparts .
However, the body usually adapts by reducing gut absorption and increasing bile excretion. These mechanisms can work remarkably well, even in preterm infants .
2) Those on Parenteral Nutrition
Parenteral nutrition solutions (IV solutions) are routinely used in critically-ill and preterm infants who cannot tolerate oral feeding. These solutions can contribute to excessive Mn levels .
In newborns on total parenteral nutrition, Mn burden can be increased by 100-fold, compared to breastfed infants .
Mn toxicity has also been reported in adults receiving long-term parenteral nutrition. In such cases, manganese can build up in the brain and this can be detected before any symptoms arise. Stopping parenteral nutrition lowers Mn, allowing for it to be cleared from the brain [18, 76].
3) People with Liver Disease
Patients suffering from liver failure are at risk since their main manganese removal system – the production and flow of bile – isn’t working .
Any existing liver damage may delay or decrease manganese elimination, in turn, increasing its blood levels .
People with liver cirrhosis have increased blood and brain manganese. One MRI imaging study also measured higher brain manganese in those with liver dysfunction and liver failure .
4) Iron-Deficient People
Iron has a strong influence on manganese balance. Both metals share transporters (transferrin and DMT1) . Iron deficiency increases the production of these transporters and, inadvertently, the accumulation of Mn .
Children breastfed for prolonged periods of time are at risk of iron deficiency and may have higher blood Mn levels .
According to the 2011 – 2012 NHANES study of US residents, women have significantly higher blood manganese levels than men .
Additionally, the 2011 – 2012 NHANES showed that pregnant women accumulate even higher Mn levels .
6) People with Neurological Diseases
Those with pre-existing neurological diseases may be at higher risk of developing Mn toxicity, because of the potential for combined effects .
7) Patients with Kidney Failure
Chronic kidney failure on dialysis may develop manganism even of their overall external exposure is low .
8) People with Occupational Mn Exposure
Finally, Mn toxicity can occur in rural workers exposed to Mn-containing pesticides such as maneb .
9) People with Rare Genetic Mutations
Mutations in these genes can cause high manganese blood levels (hypermanganesemia) and Mn buildup in the brain, resulting in movement disorders, liver disease, low iron, and high red blood cell mass (polycythemia) [89, 90].
Sources of Manganese
- Whole grains
This metal is also found in seafood, seeds, chocolate, tea, leafy green vegetables, spices, soybean, and some fruits such as pineapple, blueberries, and acai. However, all these foods are generally healthy and avoiding them is not a good idea [21, 2, 79].
Various supplements and multivitamins often contain manganese. Most people already have more than an adequate intake of Mn, and should be careful when supplementing this metal.
Around the web, Mn is discussed as a histamine-lowering and dopamine-increasing agent, although there is little research to support this. In fact, manganese may actually decrease dopamine in the long run [18, 92].
Manganese supplements can cause a short-term boost in energy, but people often report side effects such as emotional instability, mood issues, racing pulse, nausea, and fatigue.
You should especially be careful if your liver is not functioning properly, because that makes you prone to Mn accumulation and toxicity.
As a plant-rich diet provides more than enough manganese for most of us, you may want to skip on Mn and opt for other supplements that can provide the same benefits but without the toxic effects.
Water, Air, and Other Sources
Overexposure to Mn can occur through diverse sources, including drinking water, industrial pollution, and mining wastes .
Approximately 5.2 % of the 2,167 wells surveyed across the USA exceeded the health benchmark of 300 µg/L Mn .
In the industry, the majority of Mn is used to make alloys and steel. Mn is also used in the manufacturing of dry cell batteries, fuel additives (MMT), fungicides (e.g., maneb and mancozeb), paint, adhesives, ceramics, cosmetics, leather, glass, and textiles [2, 5, 93].
Ways to Combat Manganese Toxicity
Substances that help with manganese toxicity include antioxidants, plant extracts, chelating agents, precursors of glutathione (GSH), and synthetic compounds .
- The best way to keep your Mn levels in check is to make sure you take adequate amounts of iron. High-iron diets suppress Mn absorption .
- Calcium can also help decrease manganese absorption .
- Taurine improves the impairment of learning and memory caused by excessive Mn in rats . You can find taurine in energy drinks.
- Vitamin E and Trolox (a water-soluble analog of vitamin E) protect animal brains from the toxic effects of Mn .
- Magnesium [97, 98, 99, 100]
- Glutathione (GSH) (in cell studies) 
- N-Acetylcysteine (NAC), a precursor of GSH (in cell studies) [101, 102]
- Melatonin (in mice and cells) [103, 104]
- Quercetin (in rats) [105, 106, 107]
- Acai – although acai (Euterpe oleracea) on its own is a source of Mn, its extract protected rat brain cells from Mn-induced oxidative stress. These protective effects are likely due to the antioxidant and anti-inflammatory effects components in the berries 
- Lemon balm (Melissa officinalis) extract (in mice) 
- Milk thistle (Silymarin) (in rats) 
- Lycopene (in rats) 
- Curcumin (in cells) 
- Chelating agents, such as calcium disodium salt of the chelator EDTA (in humans and rats) 
Anti-inflammatory compounds, such as ibuprofen (in rats) 
If you already got your manganese blood levels checked, LabTestAnalyzer helps you make sense of your results. It informs you which labs are not in the optimal range and gives you guidance about how to get them to optimal. It also allows you to track your labs over time. No need to do thousands of hours of research on what to make of your lab tests.
LabTestAnalyzer is a sister company of SelfHacked. The proceeds from your purchase of this product are reinvested into our research and development, in order to serve you better. Thanks for your support.
Getting more manganese than you need can cause serious health problems. Manganese toxicity leads to brain damage, mental health issues, and hormonal imbalances.
If you suspect you’re taking in more than you need, there are a couple of steps you can take.
First of all, check for sources of environmental exposure – your workplace, home, or drinking water may be excessively high in this metal.
You can also make simple dietary changes to lower your manganese burden, such as upping your intake of iron- and calcium-rich foods. Supplements containing plant antioxidants and magnesium can also help.