A new study has found that caffeine is unsafe for pregnant women and those trying to conceive, and its lead is calling for a “radical revision” of guidelines.
Prof Jack James, of Reykjavik University in Iceland, drew his research from 48 studies into miscarriages, stillbirths, low birth weights, early labour, and childhood acute leukaemia and obesity.
Thirty-two of the studies found that caffeine significantly increased risks of all these outcomes, except for early labour and childhood obesity.
But some did find significant association between caffeine consumption and overweight children.
Side effects of excessive caffeine intake are well known and range from headaches and nausea, to increased heart rate and sweating.
But until now, health authorities in the UK and the US advised that 200 milligrams of caffeine a day does not harm babies.
"Chronic exposure to any chemical during pregnancy is cause for concern," said Prof James, whose study was published in the British Medical Journal.
"There should be no exception simply because that chemical, caffeine, happens to be widely consumed."
"Caffeine is a habit-forming substance of no nutritional value. If anything, its widespread consumption suggests that it should be given special attention."
The new findings could be a blow to the global caffeine industry, which in 2018 was estimated to be worth $202 billion (Dh742bn).
The British Coffee Foundation estimates that 500 billion cups are drunk around the world each day.
One cup of coffee contains an average of about 100mg of caffeine.
Cause not proved but there is ‘substantial cumulative evidence’
The study was observational and so unable to prove direct cause.
Prof James says the results could be affected by factors such as inaccurate recollection of how much caffeine was drunk, smoking and, most importantly, pregnancy symptoms. Nausea and vomiting in the early term are signs of a healthy pregnancy, and women who experience them are likely to reduce their caffeine intake.
Despite these variables, Prof James says several of the reviewed studies found no threshold for caffeine consumption that did not harm babies.
"Certainly there is no evidence to suggest that caffeine benefits either mother or baby," he said.
"Therefore, even if the evidence were merely suggestive, and in reality it is much stronger than that, the case for recommending caffeine be avoided during pregnancy is thoroughly compelling."
"Specifically, [the evidence] supports pregnant women and women contemplating pregnancy being advised to avoid caffeine," he said.
Prof James said it was important for the public to understand that caffeine was not the benign substance it was portrayed to be.
"The idea that there is a safe level of maternal caffeine consumption is a myth that is strongly at odds with the scientific evidence," he said.
"This accepting attitude towards caffeine and pregnancy must change."
