Manganese and its effects on pregnancy have not been well studied.
Although manganese is an important nutrient, optimal levels during pregnancy are not known, but deficiency is very rare due to its abundance in a wide variety of foods.
It is known, however, that too much exposure to manganese via supplementation or through the environment (i.e. employment, well water) could cause potential problems during pregnancy.
Women who are concerned about their occupational exposure to manganese, or manganese levels in their well water, should talk to their health care provider (HCP) (see Resources).
Background
Manganese is derived from the Greek word for “magic”, as the nutrient plays an important role in the metabolism of carbohydrates, proteins, and fats, the formation of collagen (for wound healing), cartilage, and bone, immune function, regulation of blood sugar, reproduction, digestion, and blood clotting.
Despite its importance, manganese is one of the least studied micronutrients, and information regarding manganese and its effects on pregnancy are even more limited. Further, its effects on pregnancy are probably more complex than other nutrients since manganese is both nutritionally essential and potentially toxic.
Humans obtain nutritional manganese through food sources and supplements. Manganese exposure can also occur in the environment through the air, soil, and drinking water, and is used in fireworks, dry-cell batteries, fertilizer, paints, and cosmetics.
Pregnancy
There is very little research regarding the benefits of manganese in pregnancy. However, a study published in June 2021 found that higher levels of selenium or manganese in the mothers’ blood were associated with lower blood pressure readings in their children at clinic visits 3 to 15 years later, likely due to their antioxidant properties. Manganese may lower blood pressure in part by countering a blood pressure-raising effect of another heavy metal, cadmium.
However, manganese can also be harmful. Some research indicates supplements should be avoided or used with caution, as excess could have toxic neurological effects on the developing brain (such as neural tube defects) and raise the risk of preterm birth and/or intrauterine growth restriction. Further, no beneficial effect of manganese supplementation has been identified, outside of severe deficiency.
Currently, there are no recommended values or guidelines for ideal urinary or blood levels during pregnancy (daily intake recommendations are below), and deficiency is very, very rare.
Pregnant women can potentially have toxic exposure to manganese in the environment through well water or certain types of factory work:
Certain occupations like welding or working in a factory where steel is made may increase the risk of being exposed to high levels of manganese (through its dust), which can cause neurological problems.
For example, manganese dust has been recognized as a problem in the Southeast Side of Chicago since 2016 from industrial contamination.
NOTE: Toxicity from dietary exposure has not been reported.
Well Water
Elevated concentrations of manganese in ground water (well water) is common worldwide and can cause subtle toxic effects that may impair fetal growth.
In the United States, the Environmental Protection Agency recommends 0.05 milligrams (mg)/Liter (L) as the maximum allowable manganese concentration in drinking water. The amount of manganese in drinking water varies by location.
Moderate to severe manganese toxicity in adults (which appears over a period of months to years) can result in tremors, difficulty walking, muscle pain, fatigue, memory problems, and facial muscle spasms (similar to Parkinson’s).
It is well documented that water can be polluted with manganese contaminants and cause symptoms within just a few months, with exposure levels of 1.8 to 14 mg/L.
A 2016 study found that more than one million people who rely on well water in parts of Virginia, North Carolina, South Carolina, and Georgia reside in an area in which soil manganese concentrations are exceptionally high with water containing unhealthy manganese levels.
People who smoke tobacco or inhale second-hand smoke are exposed to manganese at levels higher than those not exposed to tobacco smoke.
Share tweetSupplementation
Manganese is present in such a wide variety of foods that deficiency is exceptionally rare and has not been reported (outside of experiments). Therefore, routine supplementation is not recommended during pregnancy.
Daily allowance/adequate intake recommendations vary greatly, likely due to a lack of research. Estimates are between 1.8 and 5 mg/day for both pregnant and non-pregnant adults; the tolerable upper dietary limit for manganese in adults is 9 to 11 mg/d. However, less than 5% of dietary manganese is absorbed.
Food Sources
Plant sources have much higher manganese concentrations than animal sources. Rich sources of manganese include whole grains, rice, hazelnuts, almonds, pecans, chocolate, tea, mussels, clams, legumes, fruit, leafy vegetables, spinach, seeds such as flax, sesame, pumpkin, sunflower, and pine nuts, and spices (chili powder, cloves, and saffron).
Action
Women who are concerned about their occupational exposure to manganese, or manganese levels in their well water, should talk to their HCP (see Resources).
Women should not take any supplements without speaking to their HCP first.
Resources
Read the U.S. Center for Disease Control’s 2012 Public Health Statement on Manganese here.
For more information regarding drinking water and having a well tested for manganese levels and other contaminants, visit the below links or call your local health department or the EPA Safe Drinking Water Hotline at (800) 426-4791.