"Our findings have potentially important public health implications in countries where a lot of black tea is consumed".
A University College Dublin study has warned that drinking large amounts of tea may be bad for an unborn baby’s health.
The research argues that tea contains a significant amount of caffeine, so it should also be taken into calculation when expected mothers are adhering to the caffeine intake limit during pregnancy.
The new study, carried out by lead researcher Ling-Wei Chen at UCD, shows a consistent link between both coffee and tea caffeine and adverse birth outcomes.
The researchers said: "Our findings have potentially important public health implications in countries where a lot of black tea is consumed, such as Ireland and the UK."
Mr Chen and his team set out to find if there is a link between maternal caffeine intake and negative birth outcomes in a population where tea is the main caffeine source.
To do this the researchers used data from an Irish cohort study.
The data, from about 1,000 Irish women, provided them with the usual dietary intakes of caffeinated products during early pregnancy.
Next they matched that information with the women’s newborns hospital records to get information on the health and birth size of their babies.
Tea was the predominant caffeine source for 48pc of pregnant women followed by coffee at 39pc.
And their findings, published in The American Journal of Clinical Nutrition, showed that that both tea and coffee lead to adverse birth effects.
So what are the risks?
Those mothers who had higher caffeine consumption showed the risks of a low birth weight or short gestational age at birth were about two times higher.
The results were similar regardless of the caffeine source (tea or coffee).
In a statement, the UCD researchers said: “These findings and other study results, are from observational studies, and observational studies cannot prove that caffeine causes these outcomes, only that there is a link between them.
“To prove causation, scientists would need to conduct randomised controlled trials. However, to do so might be deemed ethically dubious.”
While coffee is clearly the main source of caffeine in most parts of the world (about 100mg per cup), it is less recognised that tea contains a significant amount of caffeine, too (about 33mg per cup).
