Letter to the editor in response to article “Consumption patterns of nonnutritive sweeteners among university students at a Caribbean Institute”

Webb et al conducted a survey in a population of 196 university students investigating the usage levels and awareness of health effects of non-nutritive sweeteners (NNSs). From this study, the authors claim that students were largely unaware “that NNS does cause cancer” and largely aware “that NNS are associated with weight gain”. The reporting of this study infers that the investigators directly asked the student participants if they were aware that NNS cause cancer and/or aware that NNS are associated with weight gain. The publication by Webb et al is misleading with regard to understanding the health effects of use of NNSs. Regulatory food safety authorities worldwide consistently confirm that NNSs are safe, and do not cause cancer. While there has been much conversation regarding the potential for NNSs to cause weight gain, such an effect has been refuted by collective evidence from randomized controlled trials (RCTs) – the most reliable type of research for evaluation of proposed effects. Webb et al cite a recently conducted scoping review by Lohner et al when claiming that NNS use can cause cancer. While this review lists certain types of studies that investigated the carcinogenicity potential of NNSs, Lohner et al did not conclude that these studies were evidence that any NNS causes cancer. Moreover, the purpose of the Lohner et al paper was aimed only at mapping outcomes from human data, and from this, suggesting health outcomes about which systematic reviews should explore. This scoping review, due its design, also did not give consideration to either the quality of the studies listed (e.g., RCT vs observational studies) or the significant body of pre-clinical research required by regulators. Again, based on the totality of the available evidence, regulators around the world consistently confirm that NNSs are non-carcinogenic. In addition, a systematic review and meta-analysis (Toews et al), commissioned by the WHO and conducted by the same Cochrane research group that published the scoping review by Lohner et al, found no evidence of association between NNS consumption and several forms of cancer. Further reviews of particular NNSs have also shown no evidence of carcinogenic potential. Similarly, the research cited by Webb et al does not fairly represent the totality of evidence regarding the potential for NNSs to cause weight gain. While there have been numerous hypotheses generated about how NNS might cause excess weight gain in humans, collective results from RCTs do not show that NNS use would cause weight gain. Indeed, results of RCTs overall indicate that use of NNSs can help in lowering excess body weight. For example, a systematic review and meta-analysis of RCTs on NNS, energy intake and body weight concluded that: “Overall, the balance of evidence indicates that use of LES [low-energy sweeteners] in place of sugar, in children and adults, leads to reduced energy intake and body weight”. While there have been some observational studies reporting a positive association between NNS intake and obesity, such studies are not designed to evaluate causality. Moreover, it has been noted repeatedly that interpretation of data from observational studies, with regard to NNS use and body weight gain, is difficult, as reverse causality can exist. That is, the association of use of an NNS with weight gain may be the result of using an NNS in response to gaining weight and not the other way around. Hence, it is imperative to consider the collective body of evidence, and to rely on more definitive studies, such as RCTs, when considering the potential for an NNS to cause weight gain. Webb and colleagues rightly point out that excess body weight can lead to serious health complications for both children and adults. At a time when the rates of obesity continue to increase worldwide for all age groups, health organizations recommend the reduction of free sugars intake to less than 10% of energy intake. The availability of approved NNSs can help achieve this goal, and aid in sound weight control strategies. Given this, and the fact that allegations about NNSs made by Webb et al are not supported by the collective scientific evidence, such claims are irresponsible. High standards in research design and publication are necessary to ensure a balanced interpretation, context, and reporting in research on NNS.