Francisco Guarner
Director of the Digestive System Research Unit at the Vall d'Hebron University Hospital in Barcelona and former president of the Spanish Society of Microbiota, Probiotics and Prebiotics (SEMiPyP)
It is neither definitive nor of high quality. They observed discrete alterations in the tolerance test after oral glucose overload in 20 individuals after two weeks of taking 180 mg of saccharin daily, or in 20 individuals after taking 102 mg of sucralose daily, compared to 20 controls [who did not take any sweetener]. The number of individuals in each arm [those taking a particular sweetener or serving as controls] is very small (N=20), although the study includes 120 in total.
It is important to underline that they do not detect this negative effect in individuals treated with stevia or aspartame. Therefore, the discrete negative effect should not be attributed to all sweeteners.
There are many discrepancies with the existing evidence. The new publication is not a clinical study, but an experimental study: the N (the number of individuals in the study) is small, they did not enrol people with insulin resistance and they use exorbitant doses of sweetener. This is a very important limitation: 180 mg of saccharin a day for two weeks is equivalent to taking 50 tablets or 18 sachets of saccharin every day. I do not know anyone who takes such quantities. In the case of sucralose, the intervention would involve taking 20 sucralose tablets every day. Nobody does that.
Personally, I am of the opinion that there is only one acceptable conclusion, which is also important: the fact that a substance is not absorbable and therefore does not enter the blood does not mean that it is inert. The substance influences the microbiota of the large intestine and can induce negative or positive changes.