consumption in mice and humans increased the risk of glucose intolerance through modulation of both the functionality and composition of the gut microbiota (Suez et al., 2014). It has been proposed that such effects may underpin suggested links between sweeteners and increased diabetes risk; however, this is a new emerging concern and further research is required. NNS can also be unacceptable to certain consumer groups; for example, those suffering from phenylketonuria (a rare metabolic disorder) must avoid aspartame.