Why use low calorie sweeteners? Is there any health benefit after all?
Author(s): Vicky Pyrogianni, MSc, Dietitian – Nutritionist Scientific Director, International Sweeteners Association (ISA) |
Posted: 11 January 2019
A critical appraisal of the BMJ paper by Toews et al that claimed no benefits or harms for low calorie sweeteners
- Health benefits of low calorie sweeteners are clear when used to replace sugars in the diet: they help reduce calorie intake, they do not cause a spike in blood glucose, and they do not contribute to tooth decay
- The study by Toews et al did find some benefits for low calorie sweeteners’ use over sugar in both adults and children but called for more research as current evidence is weak
- It should not be expected that low calorie sweeteners, by themselves, would act as magic bullets in weight loss, but they can be useful when used to replace sugar calories
A recent review published by Toews and colleagues in the British Medical Journal (BMJ) in early January 2019 gained widespread media attention and led to headlines in mainstream media such as “sweeteners have no health benefits over sugar”, “no benefits, no harms for sugar substitutes”, “sweeteners: not good, not bad”. But do these headlines reflect the actual outcome of the systematic review by Toews and colleagues or what the collective evidence (some of which has not been considered in this new review) shows? The answer is simply no.
What did the study find?
So, first of all, let’s have a careful look at what the systematic review and meta-analyses by Toews et al actually found, based on the analysis of 56 studies including 17 randomised controlled trials (RCTs), which provide higher quality of evidence.
- In adults, mean daily energy intake was about 250 calories lower in people consuming low calorie sweeteners than in those receiving sugar, based on the study’s meta-analysis of four RCTs. Similarly, sugar intake was also found to be lower in consumers of low calorie sweeteners. Also, current studies show no effect on feelings of hunger or on appetite.
- Evidence indicated a small beneficial effect of low calorie sweeteners on body mass index (BMI) and fasting blood glucose, but this is based on a limited number of clinical studies included in the review (5 RCTs). However, due to the inclusion criteria set by the authors, important, large and well-designed RCTs of longer duration were excluded from their analysis. So, for example, the recent 1-year trial by Peters et al. (2014, 2016) that studied the impact of daily consumption of low calorie sweetened drinks on body weight in 303 participants, and which showed a clear benefit of diet drinks in weight loss and maintenance, has not been considered in the Toews et al analysis.
- When the meta-analysis estimated effects of low calorie sweeteners on overweight and obese people specifically, their use resulted in reduced body weight of approximately 2kg (3 RCTs), which could be an important benefit for individuals who need to pay more attention and manage their weight.
- Among children, the intake of low calorie sweeteners led to a smaller increase in body mass index z score than sugar intake, but no difference was found on body weight.
- No other statistically or clinically relevant health effect of low calorie sweeteners’ intake has been found, including no increased risk for cancer. The safety of low calorie sweeteners has been repeatedly confirmed by regulatory authorities around the world.
So, the review by Toews et al did find some benefits for low calorie sweeteners in relation to calorie and sugar reduction, modest weight loss and fasting glucose reduction. Not unexpectedly, these benefits have been found when low calorie sweeteners are compared to sugar. Low calorie sweeteners, by themselves, have no weight- or glucose-lowering properties, so their benefits are evident when used to replace sugars and thus calories in the diet.
The authors of the review also point out that the level of evidence is of very low to moderate quality and more longer-term studies are required, and thus they conclude that: “There was no compelling evidence to indicate important health benefits of non-sugar sweetener use on a range of health outcomes.” New large studies are indeed ongoing (e.g. Masic et al, 2017) and will certainly help in providing further evidence about the benefits of low calorie sweeteners. But on the other hand, some of the existing studies of long-term design have been excluded from the analysis of Toews et al, and therefore this exclusion is one important limitation that lowers the strength of the current review.
Commenting on the study by Toews et al in an editorial published in the same issue of BMJ, Vasanti Malik states that, “the weight of evidence hints at benefits, but the full picture has yet to emerge” (Malik V, 2019).
What the collective evidence shows?
Previously published systematic reviews and meta-analyses that have examined the totality of the published studies investigating the effects of low calorie sweeteners on body weight, and importantly have examined these effects in relation to caloric sweeteners, confirm the beneficial effects of low calorie sweeteners in calorie reduction and in modest weight loss when used to replace sugar (Rogers et al, 2016; Miller and Perez, 2014). In fact, the methodological and clinical inclusion and exclusion criteria used in these previously published systematic reviews differed substantially from the criteria of the latest review, resulting in a largely different and limited pool of included studies in the Toews et al paper. For example, the Rogers et al meta-analysis included 10 trials with 12 comparisons that examine effects on body weight versus 5 trials in the Toews et al paper; the number of included studies is much higher for short- and longer-term effects on energy intake. Also, another notable issue with the selected inclusion criteria of the Toews et al review is that by not placing any restrictions on study design, this strategy allowed the inclusion of cross sectional and non-randomised designs that are prone to confounding and reverse causation, as well as case control studies that are vulnerable to selection and recall bias (Malik V, 2019).
Similarly, the benefit of no effect of low calorie sweeteners on blood glucose (versus sugar that causes a spike in blood glucose after consumption) has been re-confirmed in recent systematic reviews and meta-analyses (Nichol et al, 2018; Tucker and Tan, 2017). The European Food Safety Authority (EFSA) has reached the same conclusion in a scientific opinion published in 2011 supporting that, “Consumption of foods containing intense sweeteners instead of sugar induces a lower blood glucose rise after their consumption compared to sugar-containing foods”. (EFSA, 2011)
Finally, another important benefit of low calorie sweeteners relates to dental health, as low calorie sweeteners are not fermented by oral bacteria and thus do not contribute to tooth decay. This has also been recognised by EFSA in its 2011 opinion, which supported that “the consumption of foods containing low/no-calorie sweeteners instead of sugar contributes to the maintenance of tooth mineralisation”. (EFSA, 2011)
In conclusion, low calorie sweeteners do have benefits when used in place of sugars in the diet. The study by Toews et al does not show any different outcome, but it notices that more research is needed to confirm their effects. On the other hand, what is certainly well established is that excess sugars’ intake should be reduced and that low calorie sweeteners are a useful tool in helping people to meet this dietary goal.
- EFSA. Scientific opinion on the substantiation of health claims related to intense sweeteners. EFSA Journal 2011, 9(6), 2229. Available at: http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2229/epdf
- Malik VS. Non-sugar sweeteners and health. The weight of evidence hints at benefits, but the full picture has yet to emerge. BMJ 2019; 363: k5005 - doi: 10.1136/bmj.k5005
- Masic U, Harrold JA, Christiansen P, et al. EffectS of non-nutritive sWeetened beverages on appetITe during aCtive weigHt loss (SWITCH): Protocol for a randomized, controlled trial assessing the effects of non-nutritive sweetened beverages compared to water during a 12-week weight loss period and a follow up weight maintenance period. Contemp Clin Trials 2017 Feb; 53: 80-88
- Miller P, Perez V. Low-calorie sweeteners and body weight and composition: a meta-analysis of randomized controlled trials and prospective cohorts (391.1). Am J Clin Nutr. 2014; 100(3): 765-77
- Nichol AD, Holle MJ, An R. Glycemic impact of non-nutritive sweeteners: a systematic review and meta-analysis of randomized controlled trials. Eur J Clin Nutr 2018; 72: 796-804
- Rogers PJ, Hogenkamp PS, de Graaf C, et al. Does low-energy sweetener consumption affect energy intake and body weight? A systematic review, including meta-analyses, of the evidence from human and animal studies. Int J Obes 2016; 40(3): 381-94
- Peters JC, Wyatt HR, Foster GD, et al. The effects of water and non-nutritive sweetened beverages on weight loss during a 12-week weight loss treatment program. Obesity 2014; 22: 1415–1421
- Peters JC, Beck J, Cardel M, et al. The Effects of Water and Non-Nutritive Sweetened Beverages on Weight Loss and Weight Maintenance: A Randomized Clinical Trial. Obesity (Silver Spring) 2016; 24(2): 297-304
- Toews I, Lohner S, de Gaudry DK, Sommer J, Meerpohl JJ. Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses of randomised and non-randomised controlled trials and observational studies. BMJ 2019; 363: k4718
- Tucker RM, Tan SY. Do non-nutritive sweeteners influence acute glucose homeostasis in humans? A systematic review. Physiol Behav 2017; 182: 17-26