EXPERT REACTION: Maternal paraben exposure and childhood overweight risk

Parabens are a type of chemical that can interfere with how some hormones work in the body. They are used as preservatives in cosmetics and some food, so we are all exposed to them. These researchers set out to find out if paraben exposure in women who are pregnant influences their children’s risk of becoming overweight. They found that the children of women who had the highest levels of parabens in their body while they were pregnant were more likely to be overweight when they were 8 years old. They also showed in animals, that parabens in pregnancy can have long term effects on how appetite works. This suggests that excess paraben exposure when a mother is pregnant might cause her children to be hungrier and gain more weight as a result. However, it is still unclear just how important paraben exposure is to human health and we do not know for sure that parabens do affect appetite development in children. At this stage women who are pregnant should not be overly concerned, but where possible it might be wise to limit the use of leave-on cosmetics (like make-up) unless they say “paraben free” on the label.

The study by Leppert et al demonstrated an association between prenatal exposure to paraben and the risk of developing obesity in offspring up to the age of 8 years old. Parabens are a group of compounds that are widely used as preservatives in a variety of foods, cosmetics and pharmaceutical products due to their antimicrobial and anti-fungal properties, as well as low cost of production and low allergenic potential. These compounds are ubiquitous in the environment and in some studies, 100% of test subjects had parabens metabolites detected in various tissues and bodily fluids.

Parabens are considered to be Endocrine Disrupting Chemicals (EDC), since they are known to have the ability to interfere with normal endocrine function by disrupting synthesis, secretion, transport, binding, action or elimination of natural hormones. These hormones are involved in maintenance of homeostasis, reproduction and fetal and neonatal development.

This study demonstrated an association between maternal use of paraben-containing cosmetic products and increased urinary paraben concentration. As paraben compounds are known to cross the placenta, it is assumed that increased maternal exposure to parabens in pregnancy resulted in increased fetal exposure, which in turn was associated with increased risk of obesity development in early to middle childhood. The mechanism of this effect of in-utero paraben exposure is unknown and the authors explored this question using a mouse model. They concluded that fetal exposure to paraben may result in neuronal dysregulation of food intake via interference with normal gene function in the hypothalamus.

There are a couple of limitations that need to be addressed. Firstly, the proposed mechanism of exposure to paraben causing increased risk of obesity was elucidated in a mouse model. While it points towards a hypothesis of similar mechanism in humans, this connection cannot be automatically assumed.

In previous studies, it was found that mouse physiology may not be identical to humans when it comes to paraben metabolism. Therefore the mechanism of paraben effect on the risk of obesity in humans may be different.

Secondly, as is usually the case in epidemiological studies, the causative relationship between maternal paraben exposure and risk of childhood obesity in offspring cannot be established. An association may not translate into causation, as there may be other factors present in the group exposed to parabens, which could also explain increased rates of childhood obesity.

Further research is clearly required on the topic, especially in view of the fact that numerous cosmetic, pharmaceutical and food compounds widely used by pregnant women contain paraben. 

Wide implications

At this time, it would be advisable for pregnant women to avoid cosmetic compounds that contain paraben. Complete avoidance of paraben is not possible as its use is so widespread, but avoiding non-essential exposure seems like a prudent and easily achievable goal.

"This study looked at the effect of paraben-containing cosmetics use by the mother during pregnancy on the risk of the child being overweight. 

Parabens are a class of chemicals used as preservatives in food and cosmetics. Parabens are known endocrine disrupting chemicals – that is, they can act on the body like a naturally occurring hormone. However, their activity is much, much lower than that of estrogen. 

Human exposure to parabens occurs from use of these products and absorption through the skin. The human body quickly converts these chemicals to inactive metabolites, which are excreted in urine. We can estimate human exposure to parabens by measuring these metabolites in urine. The majority of the population have traces of parabens in their urine. There are no known health effects. 

•    Paraben exposure varies throughout the day and from one day to the next. A single urine sample is not a reliable measure of paraben exposure
•    There was no link between high paraben exposure and the child being overweight at birth (in humans)
•    There was some very weak evidence of a link between high butyl-paraben exposure and the child being overweight 2 to 8 years after birth (in humans)
•    Methyl and propyl paraben are more frequently used than butyl paraben in personal care products and food processing. Neither of these was linked to risk of overweight (in humans)
•    This study was conducted in 2008. Rules governing the use of parabens in cosmetic products have changed since then. 

Pregnant mice exposed to butyl paraben induced increased food intake and weight gain in female offspring. Male offspring were not affected. Experiments in mice provide some evidence for the same effect in humans. Studies in mice are not the same as studies in humans. 

Diet and exercise are much more important than paraben exposure in healthy weight management."