Manganese is both an essential nutrient and one that can very easily become toxic if you take too much. Manganese is needed for the following enzymes:
- Superoxide dismutase (SOD) the main antioxidant in the mitochondria where oxidative stress can be a major factor.
- Phosphoenolpyruvate carboxykinase needed to produce glucose (gluconeogenesis).
- Arginase needed in the liver to detoxify ammonia produced during amino acid synthesis.
- Alycosyltransferases, needed for normal bone and cartilage formation, and wound healing.
- Glutamine synthatase is involved in converting glutamate to glutamine.
There are studies suggesting iron and manganese share similar absorption and transport pathways, with less manganese absorption when iron is high in a meal or taken as a supplement. Increased ferritin levels (suggesting high iron stores) are associated with lower manganese absorption.
SYMPTOMS OF DEFICIENCY
No symptoms have ever been shown unless a person was intentionally fed a manganese deficient diet or were on total parenteral nutrition (fed through an IV) that was lacking manganese. In these unusual circumstances, rash, poor bone mineralization, higher calcium and alkaline phosphatase, and impaired glucose tolerance have been reported.
Manganese is highest in whole grains, nuts and green leafy vegetables. The average intake in the US is about 2 mg a day and for vegetarians and the health conscious, who eat whole grains, intake is typically around 10 mg a day. There is no RDA (Recommended Daily Allowance)
Bran cereal w/raisins (1 cup) 1.4 – 2.5
Pineapple (1/2 cup) 1.3
Nuts (1 oz) 0.6 – 1.1
Brown rice (1/2 cup) 0.9
Spinach/greens (1/2 cup cooked) 0.8
Whole wheat bread (1slice) 0.7
Sweet potato (1/2 cup) 0.6
Beans (1/2 cup cooked) 0.5
Tea (black / green) (8 oz) 0.2 – 1.6
SAFETY AND TOXICIY
Symptoms of toxicity typically begin with irritability, aggressiveness, and hallucinations and can mimic Parkinson’s disease, (tremors, difficulty walking, and facial spasms) and permanent neurological changes including impaired memory and loss of facial expression. Hypertension has been reported. Toxicity is typically after prolonged inhalation of dust contaminated with manganese and rarely from water that was high in manganese. The water that caused symptoms had 14 mg/L. There is a case report of manganese toxicity from taking supplements high in manganese (manganese, or bone and joint health supplements of chondroitin or glucosamine).
The developing brain is particularly vulnerable to manganese, so this supplement and the bone health supplements with chondroitin and glucosamine should be avoided in pregnancy and for infants. This is one nutrient to avoid in supplement form unless you are documented as deficient (perhaps by functional testing like Spectracell www.specracell.com). In minimal amounts as part of a multivitamin (not for infants) at a dose of 1-2 mg a day, this might supply needs and avoid deficiency if you are not eating a diet that includes some of the foods listed above.
This is a nutrient that is much more likely to be a toxin than one that you are suffering from a deficiency of. Since 2006, manganese (along with fluoride, chlopyrifos, dichlorophenyltrichloroethane, tetrachloroethylene, and polybrominated biphenyl ethers) has been added to the five other known industrial neurotoxicants: lead, methymercury, polychlorinated biphenyls, arsenic, and toluene. Clearly, this is a bad list to be a part of. Be very careful if you supplement manganese.
TOLERABLE UPPER LIMITS
Children 1-8 2-3
Children 9-13 6
You can learn more about manganese at the following links: