While manganese can sometimes be considered toxic, prenatal exposure may be linked to better memory at adolescence.
Early-life exposure to manganese may improve verbal learning and memory skills by adolescence, according to the authors of a recent paper published in Neurotoxicology and Teratology. The period during which a child was exposed to manganese may impact neurodevelopment and cognition at adolescence, however most of the associations between manganese and cognition remain null, and more research is needed.
“There was some evidence that manganese is beneficial for verbal learning and memory in adolescence,” said study senior author Birgit Claus Henn, associate professor of environmental health at Boston University School of Public Health (BUSPH), in a press release. “In early life, it makes sense that we might need more manganese for growth and healthy development, but as we get older, the need for manganese might change.”
Manganese can be considered both an essential nutrient and a toxic chemical, depending on a variety of factors. The most common means of manganese exposure include diet, water, supplements, or environmental factors, however the relationship between manganese exposure and neurotoxic effects is lesser known.
BUSPH investigators conducted the study to understand if the timing of manganese exposure (prenatal vs early childhood) may impact susceptibility to its potential neurotoxic effects—in essence, researchers aimed to understand where the line is drawn between manganese being a beneficial or harmful chemical for brain development.
This is the first study to evaluate the effects of manganese exposure on verbal learning and memory in late childhood, particularly evaluating the effects of exposure during the prenatal period and up until early childhood. The team collected data from 140 adolescents (aged 10 to 14 years) in Italy who were a part of the Public Health Impact of Metals Exposure (PHIME) study from 2007 to 2014; they had been exposed to manganese because they lived near a ferroalloy plant.
The team evaluated learning and memory by looking at the cohorts’ neurobehavioral assessment scores, and they also evaluated patient baby teeth data collected from trimester 2 to age 6.
“The tooth biomarker allowed us to measure retrospective exposure during multiple exposure periods spanning distinct developmental stages,” Henn said in the press release. Claus Henn explained further that this allowed researchers to identify a possible link between the time of exposure and neurobehavioral outcomes.
Prenatal tooth manganese was associated with less memory and learning error, as was childhood tooth manganese. However, tooth manganese from birth to age 1 was not associated with better memory at adolescence.
Children in the first year of life might not have the same sensitivity as children in the prenatal period to manganese-related cognition changes, according to investigators; this may explain the null association. Moreover, there may be a possible association between manganese exposure and beneficial neurobehavioral outcomes in males, regardless of prenatal vs childhood exposure.
Larger cohorts are needed to further examine the association between early-life exposure and behavioral outcomes. In addition, other studies could look at the relationship between teeth biomarkers and manganese in the environment and our diets, according to Claus Henn.
“It would also be useful to look more comprehensively at impacts on the brain, because verbal learning and memory is just one aspect of neurobehavioral functioning,” Henn said in the press release.
Early-life exposure to manganese may be beneficial to adolescent cognition. Boston University School of Public Health. News Release. November 6, 2023. Accessed on November 10, 2023. https://www.eurekalert.org/news-releases/1007175