Manganese deficiency is exceedingly rare in healthy people eating a normal diet, but when it does occur, its symptoms span a surprisingly wide range of body systems. Impaired bone development, abnormal blood sugar handling, increased seizure susceptibility, reproductive problems, and weakened intestinal barriers have all been linked to insufficient manganese in both human cases and animal studies. The rarity of outright deficiency has made it difficult to compile a neat symptom checklist the way you can for, say, iron or vitamin D, and much of what we know comes from controlled animal experiments or from a handful of genetic conditions that disrupt manganese transport in humans.
Why Manganese Deficiency Is So Uncommon
Manganese is needed only in trace amounts, and it is widespread in foods like whole grains, nuts, leafy greens, and tea. The body stores enough in the liver and bones that a short-term dietary shortfall rarely causes trouble. Even people receiving all their nutrition intravenously through parenteral nutrition (PN) are unlikely to become deficient, because the solutions and equipment used in PN are typically contaminated with enough manganese to meet basic needs on their own.1PubMed Central. Manganese Provision in Parenteral Nutrition: An Update That quirk of accidental contamination helps explain why confirmed human deficiency cases are so few. The symptoms described below therefore draw heavily on deliberate depletion experiments in animals and on a small number of human genetic conditions, with a few older controlled human studies filling in gaps.
Bone and Joint Abnormalities
The most consistently documented effect of manganese deficiency is impaired skeletal development. Manganese is a required cofactor for enzymes that build and maintain cartilage and bone matrix. Without it, the structural scaffolding of growing bone falls apart. In poultry, manganese deficiency causes a condition called perosis, marked by deformed leg bones and “slipped tendon,” where the Achilles tendon slides out of its groove at the ankle joint.2PubMed. Manganese levels and the morphology of the epiphyseal plate in broilers with slipped tendons Perosis was actually one of the earliest recognized nutritional deficiency diseases in birds.3Poultry Science. The Amount of Manganese Required to Prevent Perosis in the Chick
More recent work in broiler chicks has shown that manganese deficiency damages the growth plate of the tibia by degrading the extracellular matrix, the dense mesh of collagen and proteoglycans that gives cartilage its strength. Deficient birds had fewer chondrocytes (the cells that form cartilage), reduced proteoglycan content, and less type II collagen in the growth plate.4PubMed. Enhanced Extracellular Matrix Degradation in Growth Plate Contributes to Manganese Deficiency-Induced Tibial Dyschondroplasia in Broiler Chicks In humans, skeletal effects of isolated dietary manganese deficiency have not been well documented simply because the deficiency itself is so rare. However, in genetic manganese deficiency (discussed later), short stature and skeletal abnormalities are part of the clinical picture, consistent with the animal data.
Blood Sugar Problems and Insulin
Manganese plays a role in how the pancreas handles insulin, and animal studies show that deficiency throws blood sugar regulation off course. Rats fed a manganese-deficient diet responded to a glucose load with a pattern that resembled a diabetic glucose tolerance curve. Their pancreases released less insulin than normal in both the rapid initial burst (stored insulin being dumped) and the slower second phase (new insulin being synthesized and released).5PubMed. Manganese deficiency and toxicity: effects on carbohydrate metabolism in the rat In other words, the deficient animals were not just a little sluggish in clearing blood sugar; they showed a measurable impairment in the fundamental machinery of insulin production.
Whether this translates directly to diabetes risk in humans remains an open question. Some epidemiological studies have found lower blood manganese levels in people with type 2 diabetes, but it is hard to untangle cause from effect. Low manganese could contribute to insulin dysfunction, or diabetes itself could alter how the body handles manganese. The animal evidence, at least, is fairly clear that severe manganese depletion impairs carbohydrate metabolism.
Neurological Effects and Seizure Risk
Manganese ions help stabilize the electrical properties of nerve cell membranes. When manganese is scarce at the neuronal level, membranes may become more excitable than they should be. A study of people with epilepsy found that blood manganese levels were significantly lower in treated epileptic patients compared to healthy controls. Among those patients, the individuals with the most frequent seizures tended to have manganese levels that fell below the lowest levels seen in any control subject.6PubMed. Seizure disorders and trace metals: manganese tissue levels in treated epileptics The researchers proposed that reduced manganese at the nerve cell membrane could make existing epileptic lesions more likely to fire.
This does not mean that low manganese causes epilepsy on its own. The relationship is more nuanced: in someone who already has a brain predisposed to seizures, insufficient manganese could lower the threshold for seizure activity. It is one of those findings that sits in a gray zone between correlation and causation, but it lines up with the known biochemistry of manganese at the cell membrane.
Reproductive and Developmental Consequences
Some of the most striking effects of manganese deficiency show up in offspring when the mother is depleted during pregnancy. In mice, maternal manganese deficiency produced pups with congenital ataxia, a condition in which the animals could not coordinate their movements properly. When placed in water, affected pups could not maintain an upright position, unlike their healthy littermates. Examination of the inner ear revealed that the otoliths, tiny calcium carbonate structures critical for balance sensing, were shrunken or completely absent in deficient pups.7The Journal of Nutrition. Congenital Ataxia and Otolith Defects Due to Manganese Deficiency in Mice The severity of ataxia tracked with how long and how severely the mother had been manganese-deficient.
Manganese is needed for the enzymes that synthesize the mucopolysaccharides and glycoproteins involved in otolith formation, so the link makes biochemical sense. Fertility problems have also been observed in manganese-deficient animals, including impaired ovulation and testicular degeneration, though these effects are less well characterized than the balance and coordination deficits in offspring.
Intestinal Barrier Breakdown
A more recently discovered consequence of manganese deficiency is damage to the intestinal lining. In a mouse study, a diet lacking adequate manganese increased intestinal permeability all on its own, even without any chemical irritant being applied. The deficiency impaired the tight junctions that normally seal the gaps between intestinal cells, letting material leak through that should stay in the gut.8PubMed Central. Impact of dietary manganese on experimental colitis in mice Interestingly, this effect did not seem to work through changes in the gut microbiome. The bacterial communities looked similar regardless of manganese status; the damage was happening at the level of the intestinal cells themselves.
Separately, research on a common genetic variant in the manganese transporter SLC39A8 has connected impaired manganese delivery to the colon with disrupted intestinal barrier function and a damaged glycocalyx, the protective sugar-rich coating on intestinal cells. Mice carrying this variant were more sensitive to intestinal injury and developed worse colonic inflammation when challenged.9PubMed Central. A missense variant in SLC39A8 confers risk for Crohn’s disease by disrupting manganese homeostasis and intestinal barrier integrity This line of research has drawn attention because the same SLC39A8 variant has been identified as a risk factor for Crohn’s disease in human genetic studies. It offers a plausible tissue-level mechanism linking a trace mineral to inflammatory bowel disease.
Genetic Manganese Deficiency in Humans
The clearest window into what manganese deficiency actually looks like in living humans comes not from dietary studies but from rare inherited mutations. Three transporter genes are known to disrupt manganese balance when mutated. Two of them, SLC30A10 and SLC39A14, cause manganese to build up to toxic levels. The third, SLC39A8, does the opposite: it impairs the body’s ability to absorb and retain manganese, producing a true deficiency state.10PubMed Central. Genetic Disorders of Manganese Metabolism
SLC39A8 mutations cause a congenital disorder of glycosylation, a condition in which the body cannot properly attach sugar chains to proteins, because manganese-dependent enzymes are needed for that process. The clinical presentation in affected children includes developmental delay, intellectual disability, failure to thrive, seizures, low muscle tone, eye misalignment (strabismus), cerebellar atrophy, and variable short stature.11PubMed Central. Autosomal-Recessive Intellectual Disability with Cerebellar Atrophy Syndrome Caused by Mutation of the Manganese and Zinc Transporter Gene SLC39A8 Blood tests in these patients show low manganese and zinc levels in the blood alongside elevated levels in the urine, suggesting the kidneys are wasting what little is absorbed. The disorder was first characterized in affected members of the Hutterite community and in an unrelated Egyptian family.
The symptoms in SLC39A8 deficiency overlap strikingly with what animal studies predict: neurological impairment, seizures, skeletal problems, and poor growth. They also include features like hearing loss and impaired motor function that reflect the broad role manganese plays in brain development.12PubMed Central. Inherited Manganese Disorders and the Brain: What Neurologists Need to Know These cases are rare, typically identified in childhood, and predominantly described in consanguineous families or genetically isolated communities where recessive mutations are more likely to surface.
Can the Damage Be Reversed With Treatment?
One encouraging aspect of SLC39A8 deficiency is that it responds to manganese supplementation. In treated patients, the enzyme dysfunctions caused by impaired glycosylation resolved completely, and substantial clinical improvement in motor abilities, hearing, and other neurological symptoms was observed.13PubMed. SLC39A8 deficiency: biochemical correction and major clinical improvement by manganese therapy That response makes sense biochemically: if the problem is not enough manganese reaching the enzymes that need it, flooding the system with extra oral manganese can partially compensate for the faulty transporter.
The degree of reversal likely depends on timing. Neurological damage that occurs during critical developmental windows may not be fully reversible even with later supplementation, whereas biochemical abnormalities and some functional deficits can improve rapidly. Early identification matters, which is part of why the genetic basis of these conditions has received attention in the pediatric neurology literature. For the rare individual with a dietary manganese shortfall rather than a genetic one, simply restoring adequate intake through food or supplements should correct the problem, though documented cases of dietary deficiency severe enough to produce symptoms are vanishingly few.
Who Could Realistically Become Deficient?
Given that outright manganese deficiency is hard to achieve through diet alone, it helps to know the handful of scenarios where the risk is not zero. People with conditions that severely impair nutrient absorption, such as short bowel syndrome or certain forms of inflammatory bowel disease, could theoretically fall short. Individuals on highly restrictive diets that exclude whole grains, nuts, and legumes over long periods are at a slightly elevated theoretical risk, though even refined diets tend to supply some manganese.
The genetic cases discussed above represent the most clear-cut path to clinically significant deficiency. Beyond SLC39A8 mutations, common genetic variants in the same gene can subtly reduce manganese availability in specific tissues without producing full-blown deficiency. As noted earlier, one such variant has been linked to Crohn’s disease risk through impaired manganese delivery to the colon.9PubMed Central. A missense variant in SLC39A8 confers risk for Crohn’s disease by disrupting manganese homeostasis and intestinal barrier integrity This suggests that even partial, tissue-specific reductions in manganese availability can have health consequences, blurring the line between “deficient” and “adequate.”
Diagnosing Manganese Status
One reason manganese deficiency is poorly understood in humans is that measuring it is genuinely difficult. There is no simple, reliable blood test equivalent to checking serum iron or vitamin D. Whole-blood manganese levels are used clinically, but they reflect recent intake more than long-term tissue stores. A person’s blood level can appear normal even when specific tissues are running low, particularly the brain or intestinal lining. The situation is further complicated by the fact that manganese contamination of laboratory equipment and collection tubes can falsely elevate readings.
In the genetic deficiency cases, diagnosis typically involves a combination of low blood manganese, abnormal glycosylation profiles (detected through transferrin isoelectric focusing), and genetic testing confirming SLC39A8 mutations.11PubMed Central. Autosomal-Recessive Intellectual Disability with Cerebellar Atrophy Syndrome Caused by Mutation of the Manganese and Zinc Transporter Gene SLC39A8 For the average person worried about their manganese intake, though, deficiency testing is not part of routine clinical practice. The far more common concern in occupational and environmental medicine is manganese excess, not shortage.
The Distinction Between Deficiency and Toxicity
Manganese occupies an unusual position among trace minerals because its toxicity syndrome is far better characterized than its deficiency syndrome. Workers exposed to high levels of manganese dust in mining and welding develop a progressive neurological condition called manganism, with symptoms resembling Parkinson’s disease. This toxicity risk has historically received most of the research attention and public health funding, which partly explains why the deficiency side of the equation remains understudied.
The genetic disorders that disrupt manganese transporters underscore this duality. Two of the three known transporter gene mutations cause manganese overload rather than deficiency, and they produce their own severe neurological damage through excess rather than shortage.10PubMed Central. Genetic Disorders of Manganese Metabolism The body needs to maintain manganese within a narrow band: too little starves enzymes of a critical cofactor, and too much poisons the very brain structures that depend on it. For supplementation, this means that taking large doses of manganese to prevent a deficiency that almost certainly does not exist is not a harmless precaution. The margin between enough and too much is tighter than for most minerals, and the brain bears the cost of getting it wrong in either direction.
What the Animal Evidence Can and Cannot Tell Us
Much of the symptom list for manganese deficiency comes from animal experiments conducted over decades of nutrition research. Chickens developed leg deformities. Rats showed diabetic-like glucose curves. Mice gave birth to pups that could not balance. These findings are internally consistent and biochemically coherent, but they were produced under conditions of severe, prolonged depletion that a free-living human is unlikely to ever experience. Animals in these studies were fed diets with manganese stripped down to near-zero levels for weeks or months, a level of restriction that does not happen outside a laboratory.
The human genetic cases offer more direct evidence but involve a different mechanism: not an absence of manganese in the diet, but an inability to get dietary manganese into the cells that need it. The symptoms overlap enough with the animal data to suggest the underlying biology is similar across species, but the specific thresholds, timelines, and severity may differ. If you eat a reasonably varied diet, genuine manganese deficiency is not something you need to worry about. If you have unexplained neurological symptoms, seizures, poor growth in a child, or a family history of consanguinity and developmental delay, the rare genetic forms are worth investigating, particularly because manganese supplementation can produce real improvement when started early.13PubMed. SLC39A8 deficiency: biochemical correction and major clinical improvement by manganese therapy