Conducted by researchers from Dartmouth College in Hanover, NH, the study found that infants who were breastfed had much lower levels of arsenic in their urine, compared with infants who were formula fed.
"This study's results highlight that breastfeeding can reduce arsenic exposure even at the relatively low levels of arsenic typically experienced in the United States. This is an important public health benefit of breastfeeding," says lead author Prof. Kathryn Cottingham, of the Children's Environmental Health and Diseases Prevention Research Center at Dartmouth.
The researchers recently published their findings in the journal Environmental Health Perspectives.
Arsenic is a naturally occurring element found in water, rocks, soil and air, as well as in plants and animals. The most common sources of arsenic in humans is food, including some rice and dairy products, and water - particularly water that comes from ground sources, such as wells.
Exposure to arsenic at high levels has been associated with cancer, gastrointestinal disorders and other diseases. Early-life exposure to arsenic has been linked to fetal death, reduced birth weight and impaired cognitive functioning.
According to the US Environmental Protection Agency (EPA), public drinking water should contain no more than 10 micrograms per liter (μg/L) of arsenic. However, well water is not subject to EPA regulation, and in many rural areas of the US, wells are the primary source of water.
Prof. Cottingham and her team note that past studies have suggested that, even in women living in areas with high arsenic levels in drink water, arsenic concentrations in breast milk are relatively low, indicating that breastfeeding may reduce infant exposure to the element.
To test this theory, the team measured arsenic levels in the urine of 72 6-week-old infants from New Hampshire and the breast milk of nine mothers aged 18-45 who were a part of the New Hampshire Birth Cohort Study (NHBCS). In addition, the researchers measured the arsenic concentrations in the tap water of 874 homes in New Hampshire.
Overall, the team found the average arsenic concentrations in the urine of infants were low, at 0.17 μg/L. The highest concentration identified was 3.0 μg/L.
However, the researchers found that the arsenic concentrations among infants who were exclusively breastfed were around 7.5 times lower than those of infants who were formula fed. "Moreover," the authors add, "urinary arsenic increased with formula consumption and decreased with minutes of breastfeeding among infants who were not exclusively breastfed."
Though the highest arsenic concentrations identified in tap water were much greater than the highest concentrations found in powdered baby formulas, the team says the powdered formula was found to be a main source of arsenic exposure:
"Specifically, formula powder accounted for 71% of median estimated exposure in the NHBCS, suggesting that the powdered component of formula, rather than the mixing water, may be the primary source of exposure for many of the formula-fed infants in this population.
Identifying the sources of arsenic in formula powder could help reduce exposure for formula-fed infants if alternatives are available in the production process, consistent with earlier calls for greater attention to contaminants in infant formula."
The authors note, however, that drinking water from private wells is also a primary source of arsenic exposure, and that families with these wells should get their tap water tested for arsenic.
Medical News Today recently reported on a study suggesting breastfeeding - as well as many other early-life factors - could help shape an infants' immune system development.
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