Manganese Intake in Babies: Drinking Water plus Formula Can Cause High Exposures.

Several years ago, researchers at the Minnesota Department of Health (MDH) made a startling discovery: While performing an unpublished pilot study of metals in baby formula, they detected unusually high levels of manganese. The MDH had earlier sampled private wells in the state and found that nearly half of them contained manganese at concentrations over Minnesota’s health-based guidance value (HBGV) of . Now, in Environmental Health Perspectives, the Minnesota researchers report findings from a wider investigation of manganese levels in the state’s public water supplies and powdered infant formula, as well as the total exposure and potential risk to formula-fed infants.1

An essential nutrient, manganese is neurotoxic at high levels of exposure,2 and evidence suggests that infants could be uniquely vulnerable to its effects.3,4 Manganese exposures in children have been associated with neurodevelopmental outcomes that include reduced IQ, inattention, hyperactivity, and impulsivity.5,6

Manganese is added to infant formula to meet nutritional needs, but results of a new study show that the amounts in different products vary widely. When mixed with water that also contains manganese, the total concentration of the metal may pose neurodevelopmental risks to infants and young children, according to a new risk assessment. Image: © Benjamin Clapp/Shutterstock.

The new results show that manganese concentrations in Minnesota public water frequently exceeded both the state’s HBGV and the U.S. Environmental Protection Agency’s health advisory level (HAL) of . The researchers estimated that infants fed formula mixed with Minnesota public water can be exposed to the metal in potentially harmful amounts.

During their study, the researchers reviewed drinking water data for 919 public water systems in Minnesota. More than a quarter of those had manganese levels exceeding the HBGV; of those, 96 had manganese levels exceeding the HAL. First author Deanna Scher, an MDH principal epidemiologist, says MDH staff are working with water system operators to address elevated levels.

The researchers also measured manganese in 27 store-bought infant formulas, including 22 cow’s milk products, 4 soy products, and 1 amino acid product. They mixed the formula samples with deionized water and measured manganese concentrations ranging from . The highest concentration was measured in the amino acid product, and the lowest was measured in a formula made from whole cow’s milk. Levels in soy products fell in the middle.

Next, the team performed a risk assessment to determine whether exposures from formula mixed with Minnesota public water would exceed the state’s reference dose (RfD) for manganese, which is the highest daily intake that is estimated not to cause harmful effects over a lifetime of exposure.7 According to their analysis, infant exposure to manganese in reconstituted cow’s milk formula would, on average, exceed the RfD if the corresponding manganese levels in water were or higher. Similarly, manganese exposure from soy formula would surpass the RfD if mixed with public water containing manganese at levels of at least . Manganese levels in the amino acid formula exceeded the RfD even when mixed with water that was otherwise free of the metal.

The findings should be seen as a wake-up call, asserts Scher. “This is not just a Minnesota issue,” she says. “High water manganese levels are prevalent in many parts of the United States.” Nor is it just a water issue. The study showed that formula products sold in the United States contain widely varying amounts of manganese.

U.S. regulators have not set enforceable upper-level standards for manganese in either infant formula or drinking water. Neither the Minnesota HBGV nor the federal HAL are regulatory concentrations. The U.S. Food and Drug Administration (FDA) has established minimum levels in infant formula to meet nutritional needs,8 but the agency has yet to set a legal maximum for the metal.

The authors noted that, given that the FDA standard is a minimum rather than a maximum, “it may be in the manufacturers’ interest to ensure that levels are well above the legal minimum concentration, as well as labeled levels, to avoid products being found [by the FDA to be] misbranded … which can lead to product recall.”1 Thus, an unintended consequence of no maximum level may be harmful exposure levels during a vulnerable time of life, they suggested.

“This study is significant because it calls attention not only to high levels of manganese in formula, but also the important fact that many small communities have elevated manganese in their public water systems,” says Maryse Bouchard, an associate professor in the Department of Environmental and Occupational Health at the University of Montréal, Canada. Bouchard, who was not involved in the current study, has published research linking manganese exposure in drinking water to poorer memory, attention, and motor function in children.9

Scher emphasizes that residents should be aware of the manganese levels in their water—particularly if they have infants or young children. People using public water can obtain this information from their local water utility; those on private wells can test their water themselves. Scher suggests that parents consider offering formula based on cow’s milk unless medically contraindicated and take care not to add formula in excess of labeling instructions when reconstituting the products.