Non-sugar sweeteners: not good, not bad
The inconclusive results of the review by Toews et al.  suggest that we need to see better, bigger and longer-term studies of non-sugar sweetener use, to find out for sure their benefits and risks. The review  suggests that there could be some benefits in terms of preventing weight gain, but the evidence so far is not strong and does not show consistent enough results to be sure. New large studies, such as Masic et al.,  are ongoing and will certainly help in providing further evidence about the benefits of non-sugar sweeteners.
An important benefit of non-sugar sweeteners relates to dental health, as non-sugar sweeteners cannot be fermented by oral bacteria and hence do not contribute to tooth decay. This has also been recognised by the European Food Safety Authority in its 2011 opinion, which supported that the consumption of foods containing non-sugar sweeteners instead of sugar contributes to the maintenance of tooth mineralisation by decreasing tooth demineralisation. 
 Toews I, Lohner S, Küllenberg de Gaudry D, et al. 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;364:k4718.
 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;53:80-8.
 EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). Scientific Opinion on the substantiation of health claims related to intense sweeteners and contribution to the maintenance or achievement of a normal body weight (ID 1136, 1444, 4299), reduction of post-prandial glycaemic responses (ID 4298), maintenance of normal blood glucose concentrations (ID 1221, 4298), and maintenance of tooth mineralisation by decreasing tooth demineralisation (ID 1134, 1167, 1283) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2011;9(6):2229. https://www.efsa.europa.eu/en/efsajournal/pub/2229
Competing interests: No competing interests