The World Health Organization (WHO) has released new guidance on the use of non-sugar sweeteners, recommending that they should “not be used as a means of achieving weight control or reducing the risk of noncommunicable diseases.”. In this commentary, Unit PhD student Lorenzo Del Grosso examines the evidence on which the new guidance is based and what it means for consumers.

What are non-sugar sweeteners?

Non-sugar sweeteners are no-calorie or low-calorie sweeteners, which can be made artificially (e.g., aspartame, acesulfame K, and saccharin) or from natural sources (e.g., stevia). They are often used in place of sugar to sweeten manufactured foods and beverages such as soft drinks, sweets, and yogurts, as well as medicines and dental hygiene products (e.g., chewing gums). Many non-sugar sweeteners are also available as a table-top products, for example, to add to tea and coffee.

Non-sugar sweeteners have typically been marketed as healthier choices than sugars, particularly as an aid to weight loss. The idea is that because non-sugar sweeteners have no or negligible calories, using them instead of sugars – which provide 4 calories per gram and are linked with tooth decay and obesity – should reduce calorie intake, helping to prevent weight gain, obesity, and obesity-related diseases.

Why are the WHO interested in non-sugar sweeteners?

The increasing use of non-sugar sweeteners, particularly in soft drinks, has stimulated interest in the scientific evidence of their effects on health. Their widespread use may stem from a variety of factors such as personal preference, the perceived health benefits, promotion by manufacturers, or in response to recent policies designed to reduce sugar intakes.

UK policies include the 2018 UK Soft Drink Industry Levy – a ‘tax’ applied to manufacturers of sugar-sweetened soft drinks to encourage companies to reduce the amounts of sugar in their soft drinks – and the wider sugar reduction and reformulation programme.

What is the new guideline based on?

The WHO conducted a systematic review and meta-analysis to comprehensively review the available evidence on links between non-sugar sweeteners – consumed either in beverages, foods, table-top products, or capsules – and various health outcomes, and then statistically combine the results from multiple studies.

The review included over 280 studies of different designs, primarily randomised controlled trials (50 studies), prospective cohort studies (97 studies), and case-control studies (47 studies).

What were the main findings of the evidence review?

The randomised controlled trials showed that higher intakes of non-sugar sweeteners resulted in reduced calories (-136 kcal/day) and sugars (-38.4 grams/day) intakes and lower body weight (-0.71 kg). But evidence from prospective cohort studies suggested that higher intakes of non-sugar sweeteners were linked with higher BMI (0.14 kg/m²) and increased risk of obesity (76%), type 2 diabetes (23%), mortality (12%), stroke (19%), and preterm birth among pregnant women (25%). Case-control studies also found links between non-sugar sweeteners (mainly saccharin) and bladder cancer risk, but not other cancers.

Overall, the WHO concluded that any potential short-term benefits of using non-sugar sweeteners for weight control, as shown in trials, were outweighed by the potential long-term risks of obesity and chronic disease as suggested in cohort and case-control studies.

If non-sugar sweeteners don’t contain calories, how could they lead to weight gain?

The biological processes are not entirely clear, partly because studies in humans are limited. But it’s possible that using non-sugar sweeteners may not lead to the reduction in calories that we might expect, which may be due to a variety of factors.

Although non-sugar sweeteners taste sweet like sugar, the body doesn’t get the energy (calories) it then expects after tasting sweetness, which may leave us feeling hungry or unsatisfied. Continued use of non-sugar sweeteners could make us less sensitive to sweetness, leading us to choose sweeter foods, which are often high in calories. Or it may be that people justify that extra slice of cake as a treat because they’ve been ‘good’ by choosing a ‘diet’ product containing non-sugar sweeteners. This means we end up eating more food and ultimately consuming more calories.

Other research suggests non-sugar sweeteners may change the balance of bacteria in our gut, which plays a role in obesity and metabolic health.

How strong is the evidence?

It’s worth noting that the overall quality of evidence available for the review conducted by the WHO was graded as ‘low certainty’.

Findings from the randomised controlled trials give us the most confidence because they can show whether non-sugar sweeteners caused the health outcome(s). But only four of the trials lasted for more than a year, so most did not look at long-term weight control. Most trials also did not look at the effects of switching from sugars to non-sugar sweeteners on health, which is how they may be used by consumers.

The prospective cohort and case-control studies can only find whether non-sugar sweeteners associated with the health outcome(s) but are useful to study long-term weight control and diseases which take a long time to develop, such as cardiovascular diseases and cancer. A key limitation of the cohort studies is that people who had already gained weight may have taken action to cut their calories by switching from sugars to non-sugar sweeteners. This means these studies may find that higher non-sugar sweeteners intake is linked with ill-health, when actually it was because these people carried excess weight in the first place. People consuming more non-sugar sweeteners may also have had other differences in health-related behaviours which were not fully accounted for.

Dr Nita Forouhi, Professor of Population Health and Nutrition at the MRC Epidemiology Unit, University of Cambridge, commented:

The role of artificial or non-sugar sweeteners in health is a hot topic, with unresolved questions that only better research can help to answer. We, and others, are taking forward new research in this area including identifying objective markers of their consumption rather than relying on people’s recall of what sweeteners they consumed. We look forward to positively informing the ongoing debate”

The WHO recognised that further research is needed to shed more light on these possible links, particularly in children and pregnant women.

Should I be cutting out non-sugar sweeteners?

The WHO guideline is intended to inform policy decisions rather than provide a personal target for individuals, but you may want to consider the certainty of the evidence, and why and how often you are consuming non-sugar sweeteners. The guideline does not give a maximum amount of non-sugar sweeteners to limit intake to, although if you are a frequent (e.g., daily) or high consumer, you may have more reason to consider reducing your intake compared to an occasional consumer.

When considering this guideline, you should be mindful that it does not apply to sugar alcohols/polyols (which are not considered non-sugar sweeteners because they contain calories), medicines, and dental hygiene products, or individuals who already have diabetes, who should consult a dietitian before making significant changes to their diet.

Existing WHO recommendations to limit intakes of free sugars – those added to foods and drinks or naturally present in honey, syrups, and fruit juices – also still apply. UK guidelines recommend that less than 5% of total daily calories should come from free sugars. For adults, this is around 30g or 6 teaspoons of sugars.

Because non-sugar sweeteners do not appear to be an ideal replacement for sugars, you may want to consider other ways of reducing your sugars intake. Drinking water instead of sugary drinks is a great choice, but unsweetened tea, coffee, and low-fat milks are good options too. You could try infusing water with fresh fruit or pure (100%) fruit juice if you need that hint of sweetness, but try to limit fruit juices to 150ml per day – they contain free sugars too! Consider choosing lower sugars options for breakfast cereals (e.g., porridge, wheat biscuits) and yogurts (e.g., plain natural yogurt), and top with some chopped fruit for sweetness. Reading the nutritional label (for sugar content) and ingredients lists (if you wish to identify non-sugar sweeteners) on food products is a great place to start when considering making changes to your diet.

By Lorenzo Del Grosso, MRC Epidemiology Unit.

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Additional information

Acknowledgements

Professor Nita Forouhi and Professor Jean Adams have supervised the drafting of this commentary.

Further Reading

The 2022 WHO publication ‘Health effects of the use of non-sugar sweeteners: a systematic review and meta-analysis’ on which the new guideline was based cited three studies led by researchers at the MRC Epidemiology Unit. These were:

• Barrett P, Imamura F, Brage S, Griffin SJ, Wareham NJ, Forouhi NG. Sociodemographic, lifestyle and behavioural factors associated with consumption of sweetened beverages among adults in Cambridgeshire, UK: the Fenland Study. Public Health Nutr. (2017) DOI:10.1017%2FS136898001700177X
• O’Connor L, Imamura F, Lentjes MAH, Khaw K-T, Wareham NJ, Forouhi NG. ‘Prospective associations and population impact of sweet beverage intake and type 2 diabetes, and effects of substitutions with alternative beverages’ Diabetologia (2015) DOI:10.1007/s00125-015-3572-1
• The InterAct consortium ‘Consumption of sweet beverages and type 2 diabetes incidence in European adults: results from EPIC-InterAct’ Diabetologia (2013) DOI:10.1007/s00125-013-2899-8

In addition, these studies published by researchers at the MRC Epidemiology Unit are relevant to the topic:

• Forde H, Penney TA, White M, et al. Understanding Marketing Responses to a Tax on Sugary Drinks: A Qualitative Interview Study in the United Kingdom, 2019. International Journal of Health Policy and Management (2022) DOI:10.34172/IJHPM.2022.5465
• Imamura F, O’Connor L, Ye Z, et al.  Consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice and incidence of type 2 diabetes: systematic review, meta-analysis, and estimation of population attributable fraction. The BMJ (2015) DOI:10.1136/bmj.h3576
• Imamura F, Schulze MB, Sharp SJ, et al. Estimated Substitution of Tea or Coffee for Sugar-Sweetened Beverages Was Associated with Lower Type 2 Diabetes Incidence in Case-Cohort Analysis across 8 European Countries in the EPIC-InterAct Study. J Nutr. (2019) DOI:1093/jn/nxz156
• O’Connor L, Imamura F, Brage S, Griffin SJ, Wareham NJ, Forouhi NG. Intakes and sources of dietary sugars and their association with metabolic and inflammatory markers. Clin Nutr. (2018) DOI:10.1016/j.clnu.2017.05.030