According to findings published in the American Journal of Clinical Nutrition, pregnant Danish women who consumed at least four servings of artificially sweetened carbonated soft drinks per day were at a 78 per cent higher risk of preterm birth than women who did not consume any soft drinks.
Researchers from Statens Serum Institut in Copenhagen, the University of Iceland, and Harvard School of Public Health analysed data from 59,334 women participating in the Danish National Birth Cohort. Drinking only one serving of artificially sweetened carbonated soft drinks per day was associated with a 38 per cent increase in the risk of premature birth. No associations were observed for sugar-sweetened beverages.
“Our findings suggest that the daily intake of artificially sweetened soft drinks may be associated with an increased risk of preterm delivery,” wrote the researchers. “The relative consistency of our findings for carbonated and noncarbonated soft drinks and the absence of an association for sugar-sweetened soft drinks suggest that the content of artificial sweeteners might be the causal factor.
The researchers stress, however, that their study is the first to report this association and that their findings need to be replicated "in another experimental setting" in order to confirm or reject the current results.
The use of sweeteners in food and beverage products is widespread and has gathered yet more pace as food firms seek to deliver healthier products, with less sugar, to consumers. According to Leatherhead International, the global market for sweeteners was worth US$1.83bn in 2007.
Although all the sweeteners used in the EU and US have been approved and are deemed safe by the food safety authorities, internet forums, newspaper reports and some scientific literature – including the new AJCN study – continue to promote suspicion.
The Calorie Control Council, an international association representing the low-calorie and reduced-fat food and beverage industry, said the study challenged “the weight of the scientific literature and provides misleading conclusions”.
“This study may unduly alarm pregnant women,” said Beth Hubrich, a dietitian with the Calorie Control Council. “While this study is counter to the weight of the scientific evidence demonstrating that low-calorie sweeteners are safe for use in pregnancy, research has shown that overweight and obesity can negatively affect pregnancy outcomes.
“Leading health groups support the use of low-calorie sweeteners in pregnancy. Further, low-calorie sweeteners can help pregnant women enjoy the taste of sweets without excess calories, leaving room for nutritious foods and beverages without excess weight gain – something that has been shown to be harmful to both the mother and developing baby,” she added.
These statements were echoed by the International Sweeteners Association, an organisation representing manufacturers and users of low-calorie sweeteners. “Before being authorised for use in food and drinks, all low-calorie sweeteners must undergo a range of safety evaluations by independent national and international scientific expert committees,” said the association. “These evaluations take into account potentially sensitive groups such as pregnant women, infants and children.
“There are many factors that increase the risk of premature births, such as smoking, diabetes, poor nutrition, anaemia, stress, depression and many more. They include overweight and obesity,” it added.
What they measured
The new study evaluated intakes of carbonated and noncarbonated sugar-sweetened and sugar-free/ light soft drinks and/or cola using food frequency questionnaires. Statistical analysis of the data took into account non-dietary risk factors of premature delivery, including the mother’s age, her height, her BMI prior to becoming pregnant, her cohabitant status, her smoking habits, and her familial socio-occupational status.
Lead researcher Thorhallur Halldorsson told FoodNavigator that women who developed gestational diabetes were eliminated from the study. "[However], we do not have any data at the moment on pre-existing diabetes but we are working on that issue and we will have those numbers in the near future".
Dr Halldorson added that the average age of the women was 29 and that "type-II diabetes is unlikely to be a problem and that assumption is partly supported by the fact that we observed similar effects among normal- and overweight women.
"It would have been an added strength to have numbers on type I diabetes," added Dr Halldorson.
Despite the apparently strong associations for artificial sweeteners overall, the researchers stated it was difficult to differentiate since “most artificially sweetened soft drinks include mixtures of different sweeteners”. Indeed, an earlier Danish survey found that most diet drinks in the country were sweetener with a blend of aspartame and acesulfame-K.
“Given that a mixture of artificial sweeteners are used in the production of soft drinks, the lack of studies with respect to pregnancy complications, and the controversy surrounding the health effects for some of those sweeteners, the replication or rejection of our findings in other independent data are warranted,” wrote the researchers.
Commenting on a potential mechanism, the researchers note that aspartame is broken down in the body to produce aspartic acid, phenylalanine, and methanol. A study with primates indicated that low dose methanol exposure may reduce the gestation period, said the researchers (Neurotoxicol Teratol., 2004, Vol. 26, pp. 639-650).
In response to this mechanism, the AminoSweet Information Service (AIS), the information service for Ajinomoto’s AminoSweet aspartame ingredient, said the study’s findings were “not plausible scientifically”.
“The amount of methanol produced from the aspartame used to sweeten a 330ml can of low calorie beverage is less than that contained in a small banana, and half the amount in a 220ml glass of tomato juice,” stated the AIS. “The body treats the methanol produced during digestion of food in exactly the same way no matter what its source.”
“At a time when the consequences of overweight and obesity, including in pregnancy, pose a significant challenge to public health, scare-mongering about this low calorie sweetener does the public a disservice,” stated the AIS.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.2009.28968
“Intake of artificially sweetened soft drinks and risk of preterm delivery: a prospective cohort study of 59,334 Danish pregnant women”
Authors: T.I. Halldorsson, M. Strom, S.B. Petersen, S.F. Olsen