The findings come from a two-part study published in Nature Communications, which reported that children born to women who use cosmetics containing butylparaben during pregnancy were at an increased risk of obesity – and that butylparaben can lead to epigenetic changes that may interfere with appetite regulation.
"We initially wanted to find out whether the parabens detected in urine from expectant mothers from the mother-child cohort had an impact on the development of their children's weight," explains former UFZ researcher Professor Irina Lehmann, currently at the Berlin Institute of Health (BIH) and at Charité - Berlin University Hospital.
"In doing so, we discovered a positive correlation between the concentrations of butylparaben in the mothers' urine and a higher body-mass index of their children - particularly of the daughters - until their eighth birthday."
Led by researchers from the Helmholtz Centre for Environmental Research (UFZ), the team initially analysed data from the LINA mother-child study, before using mouse and cell line models to identify epigenetic modifications that are triggered by parabens and may interfere with the natural regulation of satiety in the brain.
While the researchers have not, so far, been able to come to firm conclusions on how stable these epigenetic modifications are - or whether they can be passed on to the next generation – they do warn that use of cosmetics containing parabens during pregnancy is a risk and that the ‘unambiguous’ recommendation should be to not use such products during pregnancy.
"Bearing in mind the future health of their children, expectant mothers really should use paraben-free products during the sensitive periods of pregnancy and breastfeeding," warned Lehmann.
Parabens are commonly used as preservatives in cosmetic products – especially in creams and body lotions in order to protect against microbial growth.
However, the new study suggests parebens including methylparaben, propylparaben, butylparaben may be linked to negative effects if used during pregnancy.
"If pregnant women absorb parabens through the skin, this can lead to overweight in their children," said UFZ researcher Dr Tobias Polte, senior author of the paper.
He noted that many cosmetics products already declare to be paraben-free, but added that where there is any concern information can be obtained from the list of ingredients or using the ToxFox app, for instance.
Identifying a link
The team used data from the LINA mother-child cohort study, a long-term study conducted by UFZ to examine the significance of environmental factors in sensitive periods of childhood development for the later occurrence of allergies and respiratory diseases or overweight.
In order to find out where the butylparabens in the pregnant women's urine came from, the researchers analysed answers from questionnaires completed by the participants in the LINA study relating to the use of cosmetics used during pregnancy.
"Using the ToxFox app developed by BUND enabled us to easily and quickly check whether parabens were among the ingredients of the respective cosmetics products," said Polte.
"High concentrations of parabens in the mothers' urine were indeed associated with the use of cosmetics containing parabens - particularly those that remained on the skin for a protracted period of time, such as creams or body lotions."
To track down the underlying mechanisms of the connection the team then used a combination of cell cultures and mouse studies, initially to examine whether fat cells themselves react to high concentrations of butylparaben.
"Butylparaben did not bring about an increase in the size of the fat cells, nor did the fat cells store more fat than otherwise," said Lehmann. “It was evident that the differentiation of fat cells was not impacted by the parabens."
However, when the team simulated exposure to butylparaben during pregnancy in a mouse model the team found the same link to obese offspring.
"Just as in the LINA study, the female offspring here also demonstrated increased weight gain," said Polte. "They ate significantly more than the offspring of mice from the control group."
Because of the increased feeding, Polte and his colleagues suspected that parabens might somehow influence how hunger is regulated in the brain – and took a closer look at some of the key genes regulating hunger.
They identified a marker known as proopiomelanocortin (POMC), which is crucial in controlling the feeling of hunger, but was down-regulated in the brains of the young mice.
"The influence of parabens during gestation obviously gives rise to epigenetic modifications in the offspring that permanently disrupt the regulation of the natural feeling of satiety,” said Polte. “This means that they have a higher food intake.”
He added that epigenetic modifications that relate to the regulation of satiety are only one possible mechanism, and that inter-generational effects of environmental factors “have often been underestimated.”
“We hope that our research will help to focus greater attention on such factors in future."
Source: Nature Communications
Volume 11, Article number 561, Open Access, doi: 10.1038/s41467-019-14202-1
“Maternal paraben exposure triggers childhood overweight development”
Authors: Beate Leppert, et al
**The headline and introduction of this article have been modified to make it clear that the study relates mainly to butylparaben and the risk of obesity in children - rather than a 'risk to pregnancy'