No evidence of sugar substitutes' health benefits, finds study

Low-calorie and artificial sweeteners, increasingly added to drinks and food as the industry responds to pressure to cut sugar, may not help people lose weight and there is not enough evidence on their safety, according to a major new review.

The review, carried out by Cochrane – an international non-profit research group – aims to provide evidence for the World Health Organization, which is preparing guidance on what it calls “non-sugar sweeteners” or NSSs – a term that includes artificial sweeteners such as aspartame and low or no-calorie natural alternatives such as stevia.

“No evidence was seen for health benefits from NSSs and potential harms could not be excluded,” says the review, published in the British Medical Journal, which calls for better-quality research to be done.

Food and drink manufacturers have been under pressure from Public Health England (PHE) to reduce the sugar content of their products to help tackle the obesity crisis. PHE has asked for a cut of 20% by 2020, with a 5% reduction in the year to April 2018. The industry failed to hit that target, achieving 2% instead. Many companies have opted to use artificial sweeteners instead of sugar, particularly in soft drinks.

WHO is aiming to produce guidance on sweeteners because, it says, “their use is widespread and they continue to be heavily promoted as healthy alternatives to sugars”.

The Cochrane review was set up to answer a set of questions posed by WHO about the effects on adult and child health of consuming sweeteners and specifically the impact on obesity.

The evidence analysed in the review was not very robust, said the reviewers. They included 56 studies but said most were small and did not last long enough to come to firm conclusions.

The studies were set up to look at different types of sweeteners, measuring weight, blood sugar (glycaemic) control, oral health, cancer, cardiovascular disease, kidney disease, mood and behaviour in consumers. For most of them, there was no statistical difference in weight loss or health benefits of adults and children using higher doses of sweeteners rather than small amounts or none.

The review did not find solid evidence of any major safety issues. People who used sweeteners did not appear to have an increased cancer risk, for instance. But there was what the authors described as a “very low certainty of evidence”. More and better studies of the effects and the safety of sweeteners were needed, they said.

However, sweeteners had their uses, said PHE. “Using sweeteners is one way the food and drink industry can reduce sugar in everyday products,” said Dr Alison Tedstone, the chief nutritionist at PHE. “The evidence suggests sweeteners are safe and can help consumers make healthier choices.”

“I would say that there is no convincing evidence of clear health benefits in the general population. There might be a small benefit on weight, but we don’t have high quality data with long-term follow-up that definitely confirm this effect,” said Joerg J Meerpohl, co-director of Cochrane Germany and one of the authors.

“Finally, there is a good, and safe, alternative for people/people trying to loose weight: water, and non-/less-sweetened foods. In other words, there is no need to either add free additional sugar, or sweeteners in most instances.”

Tom Sanders, emeritus professor of nutrition and dietetics at King’s College London, said: “The findings of this study are not surprising and confirm the view that artificial sweeteners are not a magic bullet to prevent obesity. Replacement of sugary drinks with artificial sweeteners helps prevent weight gain in children but is not superior to the preferred alternative – water.”

Another expert said sweeteners were still preferable to sugar and pointed out that some large studies not included in the review showed they did help some people lose weight.

“This paper does not change my mind – non-sugar sweeteners remain far better than sugar-sweetened beverages given lack of calories in the former, and the well-known harms of the latter including in particular on dental health,” said Naveed Sattar, professor of metabolic medicine at the University of Glasgow.

“Also, the two best randomised trials ever conducted did show benefits of lower weight gain in children and adolescents when comparing diet drinks to sugar-sweetened beverages.

“The issue with this current study is that it also includes data from sources other than randomised trials and as soon as you do this, the quality of the evidence becomes far weaker and for this reason hard conclusions are near impossible to make from studies which mix different types of studies.

“The authors recognise this to some extent and I strongly agree with them when they say there is a need for higher quality and larger randomised trials in the nutritional field, however hard they may be to conduct, as, without these, some issues will never be fully resolved.”

In a linked editorial in the BMJ, Vasanti Malik, from the Harvard TH Chan School of Public Health in the US, also said more research was needed.

However, she said, based on the existing evidence, replacing sugar with sweeteners, particularly in drinks, “could be a helpful strategy to reduce cardiometabolic risk [chances of having diabetes, heart disease or stroke] among heavy consumers, with the ultimate goal of switching to water or other healthy drinks.

“Policies and recommendations will need updating regularly, as more evidence emerges to ensure that the best available data is used to inform the important public health debate on sugar and its alternatives.”