Experts argue over benefits of diet drinks
BMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j58 (Published 05 January 2017) Cite this as: BMJ 2017;356:j58
A row has blown up around the benefits of sugar-free or “diet” drinks after academics claimed, in the open access journal PLoS Medicine, that these are no more helpful than the full sugar versions for maintaining a healthy weight.1 However, other experts have criticised their conclusions and fear that they may add to public confusion.
Academics from Imperial College London and two universities in Brazil wrote in a commentary article that, although artificially sweetened beverages may be perceived by consumers as the healthier option, no solid evidence supports the claims that they are healthier or can help prevent obesity and diseases such as type 2 diabetes.
They emphasised concerns that artificially sweetened beverages may trigger compensatory food intake by stimulating sweet taste receptors. And consumers may eat more if they are aware of the low calorie content of their diet drink. The reviewers also noted that producing artificially sweetened beverages has negative consequences for the environment, as 300 L of water can be needed to produce a 0.5 L plastic bottle of a carbonated soft drink.
In March 2015 the World Health Organization published revised guidelines on sugar intake, urging national governments to institute policies to reduce sugar intake.2 Drinks companies have responded to the growing global threat of regulatory action by producing sugar-free or “diet” versions and promoting them as a healthier alternative.
Christopher Millett, senior investigator at Imperial College’s School of Public Health, said, “A common perception, which may be influenced by industry marketing, is that, because ‘diet’ drinks have no sugar, they must be healthier and aid weight loss when used as a substitute for full sugar versions. However, we found no solid evidence to support this.”
The narrative review concluded that evidence of the long term impact of sugar-free drinks on controlling weight is limited. Evidence from randomised trials has produced mixed findings, as some studies indicate a null effect while others have found modest reductions in weight, but the reviewers added that most of these studies had numerous limitations.
They also noted that industry sponsored research was common. Systematic reviews sponsored by food or beverage companies are more likely to report favourable results about the effect of artificially sweetened beverages on weight control than non-sponsored reviews, they wrote.
But Tom Sanders, professor emeritus of nutrition and dietetics at King’s College, London, said, “This article is an opinion piece rather than a systematic review of the evidence. It refutes a previously published systematic review that showed modest weight loss when full sugar drinks were replaced with artificially sweetened beverages because that review was industry funded, not on the basis of the scientific methods used.”
Russell Viner, officer for health promotion for the Royal College of Paediatrics and Child Health, commented, “As this paper acknowledges, the effect of artificially sweetened beverages on weight and other health outcomes, especially for children, is inconclusive. And, although plausible, many of the researchers’ arguments are theoretical and cannot be substantiated with existing data.
“What we do know, though, is that, regardless of any impact on weight, reducing sugar intake will have beneficial effects on dental health, which is particularly important in children.”
Susan Jebb, professor of diet and population health at Oxford University, said, “For people seeking to manage their weight, tap water is without question the best drink to choose, for health and the environment, but for many people who are used to drinking sugary drinks this will be too hard a change to make.
“Artificially sweetened drinks are a step in the right direction to cut calories.”
