This week in the news there are reports on whether coffee consumption in pregnancy could increase the chances of having an overweight child. This was picked up by the Daily Mail, The Telegraph and The Express.
The report is based on a study published this month in the British Medical Journal where it was found that any caffeine consumption during pregnancy was associated with a higher risk of excess infant growth and of being overweight in childhood.
Our opinion in brief
The study has limitations. It was not controlled and being a single study alone, we cannot say there is conclusive evidence to support the theory that drinking coffee in pregnancy leads to overweight children.
Nevertheless, current advice for pregnant women is to avoid high intakes of caffeine and stick to no more than 200mg per day.
Details of the study and findings
- 51,000 mother and infant pairs in Norway between 2002 and 2008 were studied.
- Expectant mother’s daily intake of caffeine (found in coffee, chocolate, tea and soft drinks) was measured at 22 weeks of pregnancy.
- The results were divided into the following categories:
- 1) ‘Low caffeine intake’ – less than 50mg/day (equivalent of half a cup of coffee/two thirds of a cup of tea) just less than 50% were in this group.
- 2) ‘Average caffeine intake’ – 50-199mg/day (equivalent of up to two cups of coffee/tea per day), over 40% were in this group.
- 3) ‘High caffeine intake’ – 200-299mg/day (equivalent of up to three cups of coffee/four cups of tea per day), 7% were in this group.
- 4) ‘Very high caffeine intake’ – more than 300mg/day (equivalent of three or more cups of coffee/four or more cups of tea per day), 3% were in this group.
- Children’s weight and height were measured at six weeks of age, at three, six, eight, 12 and 18 months and then at two years and every year thereafter up to the age of eight.
- The prevalence of excess growth in infancy increased from 23% to 29% as prenatal caffeine intake increased from low to very high.
- The prevalence of overweight increased by 5% at age 3 years, by 6% at age 5 years and by 3% at age 8 years with increasing prenatal caffeine exposure from low to very high.
The original study shows all the detailed findings.
Behind the headlines: the Nutrilicious dietetic view
What do we know already about caffeine in pregnancy?
High intakes of caffeine during pregnancy (more than 200mg per day or two cups of coffee or tea) can result in low birth weight babies, which can increase the chances of health problems in later life. Too much caffeine can also cause a miscarriage.
Source: National Health Service
The study, however, focuses on excessive weight gain during infancy and childhood, which is currently not a known effect associated with high caffeine intakes. We must consider the strengths and weaknesses of this study.
Strengths and weaknesses of the study
Strengths include the very large sample size on which the study was based (51,000 mother-child pairs) and also that maternal caffeine intake was estimated from all possible food sources (not just coffee).
A major weakness of the study, as with many other dietary studies, is that the data is self-reported. It relies on the honesty and accuracy of the mother reporting their caffeine intake. Additionally, measurements of height and weight after 2 years were self-reported by the mother, again reducing the accuracy of the findings.
Importantly, this study was not a controlled trial and thus we cannot prove or be certain that the caffeine intake during pregnancy was the cause of the children being overweight. There are many factors which could interfere with the results including the other attributes or lifestyles and dietary choices that the mothers may have that were in the high caffeine intake groups.
For example, it was reported that women who were in the ‘high caffeine intake’ group were more likely to have been obese before pregnancy and to have partners who were obese and smokers.
We would strongly advise that pregnant women stick to the advice from the Foods Standards Agency, which is to limit caffeine to no more than 200mg per day.
This is equivalent to about
- two mugs of instant coffee (100mg each)
- one mug of filter coffee (140mg each)
- two mugs of tea (75mg each)
- five cans of cola (up to 40mg each)
- two cans of energy drinks (up to 80mg each) or
- four (50g) bars of plain chocolate (up to 50 mg each).
Many of the headlines focus on coffee even though, as shown above, other food and drinks contain caffeine. All sources of caffeine should be considered and to ensure maximum limits are not exceeded.