Our blood sugar level is finely regulated and kept reliably within narrow boundaries. A long-term high sugar consumption often leads to overweight and can result in diseases such as type 2 diabetes mellitus. As sugar is considered unhealthy, artificial sweeteners such as aspartame and saccharin or sugar substitutes such as sorbitol or xylitol are currently used for sweetening. In comparison to ordinary sugar, these substances have no or few calories, and have a sweetening strength of at least 2 to 400 times that of sugar. They are intended to help with weight loss and contribute to stabilising blood sugar levels. But recent studies cast increasing doubt on whether artificial sweeteners are in fact healthier. For instance, a growing consumption of fast food that contains sweeteners has been linked to a higher risk of depression . Moreover, a first large-scale human study has shown that, contrary to expectations, artificial sweeteners actually influence blood sugar levels and also alter the composition of the gut flora .
This randomised controlled intervention study was carried out in 2022 at the Israeli Weizmann Institute and involved 120 test subjects. Groups of twenty healthy subjects each took a low dose of one of the four sweeteners saccharin, sucralose, aspartame and stevia over a two-week period. Two further groups were given either glucose or a placebo. The subjects' physical activity and eating behaviour were documented and a range of metabolic and microbial parameters were measured. Glucose tolerance tests were carried out at regular intervals to identify whether the sweeteners had an effect on blood sugar levels. The effect of the sweeteners on the composition and function of the gut microbiome was analysed, for example, by means of stool samples.
The study showed that consumption of saccharin and sucralose significantly increased blood sugar levels, however the biochemical processes responsible for this are unclear. The ability to regulate blood sugar, in other words, to maintain blood sugar levels within the physiological limits when consuming glucose, was thus reduced under the influence of these artificial sweeteners. In contrast, aspartame and stevia showed very minor effects.
Significant changes in the composition of the gut flora and the concentration of specific metabolites were demonstrated for all sweeteners, but the effects were not uniform. Analyses of the stool samples, for instance, showed that Krebs cycle metabolites (TCA metabolites) were increased during sucralose supplementation. The Krebs cycle is a metabolic pathway that provides energy and plays a role in the breakdown of both carbohydrates and fats and proteins. Increased concentrations of this TCA metabolite are linked to impaired blood sugar regulation. In the control groups that were given glucose or a placebo, there was no change in the gut microbiota, and the blood sugar level remained stable.
In summary it may be stated that artificial sweeteners can have a clear effect on metabolism and on the intestinal bacteria. Given this evidence, artificial sweeteners are not merely sweet. Suez et al. suspect that the gut microbiome constitutes a kind of "reaction centre". The gut bacteria react to artificial sweeteners, undergo changes and so influence human glucose tolerance through changes to the production of signal substances. Similar effects were demonstrated in further studies . However, these studies had either significantly fewer test subjects, a shorter test period or very high dosage levels of artificial sweeteners.
"Sweet" is a taste that is experienced as pleasant right from infancy. Many foods are sweet in themselves while others are sweetened with additives. There are natural sweeteners besides sugar, such as syrups made from dates, agave, maple or sugar beet, which are frequently used in baking or to sweeten foods such as muesli. Synthetic sweeteners are mainly used in soft drinks and sweets.
"Sugar" refers mainly to table sugar, sucrose, which consists of the monosaccharides glucose and fructose. When we eat foods containing sugar, enzymes start to be activated in our saliva and insulin production begins in our pancreas. Glucose ends up in the blood and provides the body with quickly available energy. Up to 75% of the glucose ingested daily is used by the brain. You could say that the brain is reliant on obtaining sugar and requires this to function. In addition, our ego organisation requires sugar in order to be present in the body, and this is the task of the blood sugar level. Our ego organisation is always dominant when we become aware of a sweet taste. If we eat artificial sweeteners, these give the impression of "sweet" and trigger the release of insulin . But no sugar arrives in our digestive system – our body has been deceived.
People who replace sugar with artificial sweeteners as part of a weight-loss diet, often start to put on weight again after losing weight for a short period. One possible reason could be this deception: the body is looking for energy which in fact is not available, which could unconsciously lead to eating more. In addition the body becomes habituated to sweetness: the more we taste sweet, the more we get accustomed to it and desire increasingly sweet foods. The different effects of the various artificial sweeteners point to the fact that our body cannot deal adequately with these artificial substances.
The consumption of artificial sweeteners is rising worldwide. In 2023 the average per capita consumption was estimated at 8.5 kg . This includes sugar substitutes such as xylitol or erythritol. These low-calorie sweeteners are often advertised as being natural and are also used in organic foods. However, these are isolated substances which have a laxative effect in higher amounts.
Sugar is part of our diet, so the question is, which sugars we eat and how much. Our body is able to obtain sugar from wholemeal products, for example. This involves active metabolism, resulting in fewer large fluctuations in the blood sugar level. If we chew a piece of bread for a long time, we taste sweet. This is a genuine sweetness that has no artificial aftertaste, unlike artificial sweeteners that sometimes even taste bitter. If we want to have a lower sugar diet, it helps to get started by becoming used to a less sweet taste. In order to reduce the amount of white household sugar, we can eat naturally sweet foods like fresh or dried fruits. These can be used to make delicious desserts and snacks. Although these minimally processed or unprocessed foods do contain sugar, it is in its natural composition. If we eat fruit and experience its sweetness, there is no deception at work, but an encounter: the foods are genuine and the body is able to process them. In this way we can move towards an honest, low-sugar diet.
 Samuthpongtorn C, Nguyen LH, Okereke OI, Wang DD, Song M, Chan AT, Mehta RS (2023). “Consumption of Ultraprocessed Food and Risk of Depression.”JAMA Netw Open. 2023;6(9):e2334770. doi:10.1001
 Suez J, Cohen Y, Valdés-Mas R, Mor U, Dori-Bachash M, Federici S, Zmora N, Leshem A, Heinemann M, Linevsky R, Zur M, Ben-Zeev Brik R, Bukimer A, Eliyahu-Miller S, Metz A, Fischbein R, Sharov O, Malitsky S, Itkin M, Stettner N, Harmelin A, Shapiro H, Stein-Thoeringer CK, Segal E, Elinav E (2022). "Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance" Cell. 185(18): 3307–28.e19.
 Iizuka K (2022). "Is the Use of Artificial Sweeteners Beneficial for Patients with Diabetes Mellitus? The Advantages and Disadvantages of Artificial Sweeteners." Nutrients. 14(21):4446. doi: 10.3390/nu14214446.
 Statista (2023). “Süßungsmittel – weltweit”.https://de.statista.com/outlook/cmo/lebensmittel/aufstriche-suessungsmittel/suessungsmittel/weltweit abgerufen am 16.09.2023
Dose below the ADI (Acceptable Daily Intake). This is derived from an estimated quantity of a substance in foods or drinking water that can be consumed daily over a lifetime without creating a marked risk to health. The ADI value differs for each artificial sweetener:
ADI value for person of 70 kg (mg/day)
Daily dose (mg) administered in six portions per day in the study
 Measurements of the body's ability to metabolise larger quantities of sugar.