July 24, 2019

expert reaction to study looking at caffeine in pregnant rats and liver development and disease in rat offspring

A study of rats, published in the  Journal of Endocrinology, reports that too much caffeine in pregnancy may impair a baby’s liver development, making them susceptible to liver disease in adulthood.

Prof Jonathan Seckl, Professor of Molecular Medicine, University of Edinburgh, said:

“This interesting paper builds upon previous research that suggests that women who consume large amounts of caffeine in pregnancy tend to give birth to babies with lower weight and have a higher risk of preterm birth or even pregnancy loss.  These effects are not massive or unequivocal, but it seems wise to suggest (as we already do) based on the totality of evidence that pregnant women avoid a heavy intake of caffeine (in coffee, tea, etc.).

“In this new work, pregnant rats were given caffeine and the researchers observed what happened to their foetuses and the subsequent offspring.  This builds on previous research by showing how caffeine in pregnancy can affect the developing liver as well as the hormones of stress in the offspring.  The research has been carefully done and the results are interesting.

“But a reality check is also in order.  The dose of caffeine given to rats ranged from the equivalent of 4-16 medium-sized cups of strong coffee a day for the average British woman.  Moreover, many of the persisting effects were only seen at the highest dose.

“It is perhaps a bit too bold to extrapolate from this work in rats to advise women to avoid all caffeine in pregnancy.  The simple advice already in place to all pregnant women to eat a balanced diet, avoid smoking, alcohol and drugs, and limit caffeinated drinks seems wise.

“Now where is my cuppa?”

Dr Amelia Lake, Reader in Public Health Nutrition, Teesside University, said:

“Current UK health advice is to limit caffeine in pregnancy.  This study doesn’t change that – pregnant women should limit caffeine and we don’t yet have the evidence to recommend completely avoiding it.

“We know that caffeine in pregnancy can cause low-birth weight which is associated with health problems later in life.

“This study, using an animal model, is suggesting that too much caffeine could be associated with long term liver development.  Animal models are important in understanding the mechanisms underlying diseases.  This fits in with what we currently know but it does give added insight.  It would be unethical to repeat this study in humans given we know the negative effects of high levels of caffeine in utero.

“The recommendation to reduce caffeine in pregnancy still stands – limit your intake of caffeine to 200 milligrams (mg) a day, approximately 2 mugs of instant coffee.”

Dr Sarah Stock, Senior Clinical Lecturer Maternal and Fetal Medicine, University of Edinburgh, said:

“This study shows that rats given large amounts of caffeine in pregnancy have pups that are smaller, and have some changes in liver development.

“Although this is an interesting study in an animal model, the relevance to human pregnancy is not very clear.  The doses of caffeine used in the study were much higher than current pregnancy recommendations.

“UK guidance is that pregnant women limit caffeine to less than 200mg a day, and most pregnant women in the UK actually consume less than this.

“Some studies in women have suggested that high caffeine intake may be linked to miscarriage and having smaller babies, so it seems sensible to keep within the 200mg per day limit.  This new animal work shouldn’t change current recommendations though.  Statements from the authors that pregnant women should avoid all caffeine seem to be over-interpreting the findings.”

Dr Michelle Bellingham, member of the Society for Endocrinology, and lecturer at the University of Glasgow, said:

“This group have previously shown in rats, that prenatal caffeine exposure can affect fetal growth, resulting in reduced birthweight of the offspring.  In this follow-up study, again in rats, they aimed to understand the underlying mechanisms.

“Their results suggest that the mechanisms underlying intrauterine growth restriction induced by maternal caffeine consumption, may involve altered development of fetal liver signalling pathways and growth factors.

“While this is an interesting and extensive study which attempts to increase our understanding of how caffeine can affect fetal development, and builds on previous knowledge that high maternal caffeine consumption may cause detrimental effects to the fetus, we must bear in mind that these results are in rats, in which caffeine may not have exactly the same effects as in humans due to inherent species differences (e.g. differences in metabolism, genetic and environmental influences).  The authors acknowledge that their findings still need to be confirmed in humans.

“The NHS has published guidelines and information on limiting caffeine consumption during pregnancy¹.  We need more research done in humans before we know whether these findings translate to people – some pregnant women may choose to avoid caffeine, which would do no harm, but that would be precautionary and isn’t warranted by this study alone.”

1 https://www.nhs.uk/common-health-questions/pregnancy/should-i-limit-caffeine-during-pregnancy/

* ‘Prenatal caffeine exposure induces liver developmental dysfunction in offspring rats’ by Bo He et al. was published in the Journal of Endocrinology at 20:00 UK time on Wednesday 24 July 2019.

Declared interests

Dr Amelia Lake: “Amelia Lake is a dietitian and a public health nutritionist who works as a Reader in Public Health Nutrition at Teesside University and is associate director of Fuse, the centre for translational research in public health.  No conflicts of interest.”

Dr Sarah Stock: “No conflicts of interest.”

Dr Michelle Bellingham: “No potentially conflicting interests to declare.”

None others received.