May 9, 2016

expert reaction to study looking at artificially sweetened drinks in pregnancy and body mass index of infants

Publishing in JAMA Pediatrics a group of researchers have reported that a mother’s consumption of artificial sweeteners during pregnancy may influence the BMI of the infant.

Prof. Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“Given the data that they had to work with, this study is statistically competent. But it’s important to be clear that their main conclusion is that “further research is warranted”, and certainly not that prospective mothers must stop drinking artificially sweetened drinks now. That’s because of the limitations that are acknowledged clearly in the press release and the study report. What the mothers ate and drank was self-reported, so maybe there are inaccuracies. But crucially, this is an observational study, so causal conclusions can’t be drawn.

“I’ll spell that out. A fairly small group of these Canadian mothers – about 5% of them – reported drinking artificially sweetened beverages at least once a day. (That includes diet soft drinks, and also tea or coffee with artificial sweetener added.) In other words, drinking these drinks once a day or more was a fairly unusual thing for Canadian mothers to do. You might expect that these unusual mothers would be different from the average in some ways, and indeed information in the study report shows that they were. For example, they were more likely to be overweight, to have smoked during pregnancy or to have had diabetes. On average they stopped breastfeeding earlier.

“The study found that this group of mothers were also more likely to have babies who were overweight at one year old. Most of them – nearly 9 out of 10 – did not have overweight babies, but the chance of overweight was about double the chance for mothers who drank very few artificially sweetened drinks or none at all. Perhaps that increased risk of overweight was indeed caused by the artificially sweetened drinks, or perhaps it was caused by something else that was unusual about the 5% of mothers. (In the jargon, perhaps the increased risk is due to confounders.) The researchers made statistical corrections to allow for differences in things they knew about, that may have made this group unusual apart from their sweetened drink consumption, such as maternal smoking and diabetes, a measure of the overall quality of their diet, the duration of breastfeeding, and several more. But they can’t know for sure that they accounted for all these things completely, and there may be other aspects of these women’s unusualness that could not be taken into account at all because they weren’t recorded.

“So a study of this nature simply can’t establish what causes the increased risk of overweight one year olds. The research report makes all this explicitly clear, and that’s really why the conclusion can’t go further than asking for more research.”

Dr Janine Elson, spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG) and Subspecialist in Reproductive Medicine and Surgery, said:

“Maternal and childhood obesity are growing problems in the UK with a quarter of women and nearly a third of children aged 2–15 classed as being very overweight or obese.

“While the study found that children of mothers who reported drinking artificially sweetened drinks during pregnancy had an increased risk of being overweight, further research is needed to confirm whether the results seen in this study can be replicated.

“Pregnant women are already advised to cut down on foods that are high in fat and sugar – including fizzy drinks – as these can contribute to weight gain. Keeping healthy during pregnancy is extremely important as a woman’s diet can impact on the health of her baby. Water is the healthiest way to keep hydrated, but some of a woman’s daily fluid intake (around 1.5 litres) can come from other drinks, such as fruit juices, smoothies and milk.”

‘Association between artificially sweetened beverage consumption during pregnancy and infant body mass index’ by Meghan B. Azad et al. published in JAMA Pediatrics on Monday 9 May 2016. 

Declared interests

Prof. Kevin McConway: “I have no conflicts of interest.”

Dr Janine Elson: “No declarations of interest.”