Higher Selenium and Manganese Levels During Pregnancy May Protect Babies from High Blood Pressure Later in Life

Children who were exposed to higher concentrations of the trace elements manganese and selenium during their mothers’ pregnancies had a lower risk of childhood hypertension, according to a study led by researchers at the Johns Hopkins Bloomberg School of Public Health and published in Environmental Health Perspectives.

Selenium and Manganese as Protection Against High Blood Pressure in Children

The researchers analyzed the concentrations of toxic metals and trace elements in blood samples from nearly 1,200 women in the Boston area who had given birth between 2002 and 2013. They found that higher concentrations of selenium or manganese in the mothers’ blood were associated with lower blood pressure readings in their children during doctor visits 3 to 15 years later. The researchers also observed that manganese had a stronger inverse relationship with children’s blood pressure when the level of cadmium—a toxic heavy metal—in the mother’s blood was higher. This suggests that manganese partially lowers blood pressure by counteracting the blood pressure-raising effect of cadmium. The findings were published in Environmental Health Perspectives.

“These findings suggest that healthy levels of selenium and manganese in the mother’s diet during pregnancy may protect her children from developing high blood pressure,” said the study’s lead author, Dr. Noel Mueller, assistant professor at the Bloomberg School’s Department of Epidemiology. “This work underscores the importance of nutrition and environmental influences in the womb on a child’s cardiovascular health. As we continue to advance this research, it could ultimately lead to updated dietary recommendations and environmental regulations aimed at disease prevention.”

High blood pressure is one of the most important modifiable risk factors for other debilitating and deadly diseases such as heart disease, stroke, kidney failure, and Alzheimer’s disease. It is also very common: the US Centers for Disease Control and Prevention estimates that about half of Americans over the age of 20 have high blood pressure—defined as systolic blood pressure above 130 mm Hg or diastolic blood pressure above 80 mm Hg—or have been prescribed blood pressure medication.

Previous research suggests that susceptibility to high blood pressure can begin early in life, even in the womb, and that protection against this susceptibility can also begin early. The researchers investigated these questions in the study: They compared the children’s blood pressure readings with the levels of toxic metals and trace elements in their mothers’ blood; they measured the toxic metals lead, mercury, and cadmium, which are associated with high blood pressure in adults; and they examined the levels of the trace elements manganese and selenium, which are associated with lower blood pressure.

Link Between Maternal Selenium Levels and Lower Blood Pressure in Children

The data set used for the analysis included 1,194 mother-child pairs from a study called the Boston Birth Cohort. The children’s blood pressure readings were taken between the ages of 3 and 15. Most of the mothers were Black (61 percent) or Hispanic (20 percent). Although previous findings have predominantly established a link between lead, mercury, and cadmium on the one hand and high blood pressure and heart disease in adults on the other, the researchers in this study found no link between these toxic metals and blood pressure in children. However, they did observe a link between maternal selenium levels and lower blood pressure in their children during childhood. For every doubling of the mother’s selenium level, the children’s systolic blood pressure decreased by an average of 6.23 points. Manganese showed a similar, albeit weaker, association with blood pressure: a doubling of exposure was associated with an average 2.62-point decrease in systolic blood pressure.

The Influence of Cadmium

Although cadmium alone was not associated with children’s blood pressure, the researchers found that higher cadmium levels in the mothers’ blood significantly strengthened the inverse relationship between manganese and children’s blood pressure. This finding suggests that manganese may specifically protect against the blood pressure-raising effects of cadmium and may even mask this effect in normal populations.

“It is often assumed that exposure to heavy metals such as cadmium only occurs in the workplace, but in fact these metals are found everywhere around us – cadmium, for example, is present in normal cigarette smoke,” says the study’s first author, Mingyu Zhang, a doctoral student in Mueller’s research group. The researchers highlighted the apparent link with cadmium and observed that manganese was much more strongly associated with lower blood pressure in children whose mothers had smoked during pregnancy. Manganese and selenium have antioxidant properties and are found in a variety of foods, including nuts and grains, leafy vegetables, fish, and seafood.