Too much sugar is known to be unhealthy: excessive consumption of the sweet substance not only increases the risk of tooth decay and obesity, but also promotes diabetes and cardiovascular diseases. For this reason, many consumers choose sugar substitutes as an alternative. However, doctors also view these artificial sweeteners critically. However, substances such as sucralose may only have harmful effects on health under certain conditions, as a study now suggests. Accordingly, the consumption of sweeteners alone is not the problem. It is only in combination with carbohydrates that disease-promoting changes occur, researchers report.
Artificial sweeteners were originally considered to be the healthy alternative to high-calorie sugar. However, sugar substitutes such as aspartame, saccharin or sucralose are now increasingly falling into twilight. There is evidence that the low-calorie sweeteners increase appetite and thus lead to overweight. In addition, they appear to be able to change the intestinal flora and metabolism after a short time and, for example, trigger glucose intolerance – a preliminary stage of diabetes. The brain could also be misled by the increased consumption of such substances: it may react differently to sweet taste in the long run and no longer adequately prepare the body for the processing of glucose or other carbohydrates, as studies suggest. How harmful the sweeteners really are is controversial. Because there are also scientific studies that could not find any negative effects. How can this discrepancy be explained?
Looking for an answer, Jelle Dalenberg from Yale University in New Haven and his colleagues have now taken the test again. For their study, they gave 45 healthy adults between the ages of 20 and 45 years seven drinks of 355 milliliters each over two weeks. The fruit flavored drinks contained either added sucralose or regular table sugar for comparison. A control group was mixed with the taste-neutral maltodextrin in addition to the sweetener. In this way, the researchers wanted to make the drink as high in calories as the sugary variant, but without adding even more sweet taste. Before, during and after the test phase, the scientists documented the test participants’ glucose tolerance and taste perception. They also used magnetic resonance imaging to check how their brains responded to sweet and other flavors such as salty and sour.
Sucralose alone has no effect
All study participants had previously consumed little or no artificial sweeteners in their everyday life. How would you react to the drinks? The surprising result: Contrary to expectations, sucralose alone had no negative impact on the measured parameters. Only the subjects who took this sweetener together with the carbohydrate maltodextrin showed significant changes. Not only did her brain react less strongly to sweet taste after the test phase. The insulin sensitivity of the body also decreased and the glucose metabolism changed. In order to trace the causes of this astonishing effect, Dalenberg and his colleagues subsequently carried out an experiment in which the test drink was only enriched with maltodextrin. But it happened: nothing.
This shows that “low-calorie sweeteners only trigger a metabolic disorder if they are consumed together with a carbohydrate,” the researchers state. It therefore appears to be this combination that damages the ability of the brain and intestine to regulate glucose metabolism. So far, experts have assumed that this effect is caused by the fact that the consumption of sweet but calorie-free foods decouples the perception of sweet taste from the calorie intake. In short: the taste no longer matches the calorie content. However, the new results now suggest that this decoupling hypothesis is incorrect. This could also explain the different study results – it depends on whether the test subjects ingested the sweeteners together with carbohydrates or not.
Light lemonade with fries – preferably not
How exactly the combined intake of sucralose and carbohydrates leads to the observed changes is still unclear. “We don’t quite understand the mechanism behind it,” says Dalenberg’s colleague Dana Small. Irrespective of this, however, practical advice can already be derived from the new findings. Because, as the scientists emphasize, the metabolic changes took place after a comparatively short amount of time and intake and are therefore transferable to common everyday situations. What does this mean specifically? “Our results suggest that it’s okay to drink diet soda from time to time,” Small explains. “But if you eat french fries, for example, you should rather have a normal lemonade – if it is not supposed to be water.”
Further studies should now clarify why exactly the combination of low-calorie sucralose and calorie-containing carbohydrate is so fatal. The researchers also want to find out whether a similar connection applies to other sugar substitutes such as stevia. If this suspicion is confirmed, this would have far-reaching implications for the evaluation of sweeteners, their health effects and common practices in the food industry. “There is a possibility that the combination effect will contribute significantly to the increase in type 2 diabetes and obesity. If this is true, the sweetness of carbohydrate-containing foods and drinks should no longer be enhanced with low-calorie sweeteners, ”the team concluded.
Source: Jelle Dalenberg (Yale University School of Medicine, New Haven) et al., Cell Metabolism, doi: 10.1016 / j.cmet.2020.01.014