Saccharin was something of the serendipities of science. A coincidence at an unexpected moment. In this case, eating bread. The accidental encounter with a sweet taste on his hands when he ate a piece of bread put on the trail the chemist Constantin Fahlberg, who was researching coal tar derivatives in his laboratory at John Hopkins University at the end of the 19th century: “No other circumstance might have been involved here, but despite my washing [de manos]somehow I had brought home the flavor of my work in the laboratory”, the researcher later recounted in some writings reproduced by the magazine of the European Association of Chemical Societies. He had found a synthetic sweetener that soon became popular on the street as an alternative to traditional sugar. But the controversy has always accompanied this sweetener in its more than 100 years of history: it was disclosed as a method to lose weight, was once associated with bladder cancer in rats —although in humans it was proven that it is metabolized differently— and its potential effects on the body are still in question today. a new study, published this Friday in the magazine Cellsuggests that they are not “inert” to the body: saccharin and other non-nutritive sweeteners, such as sucralose, can alter the microbiome – the balance of gastrointestinal microorganisms – and affect glucose tolerance.
The researchers focused on four non-nutritive sweeteners —that is, sweetening substances without caloric content—, all of them known and introduced into the human diet: saccharin, sucralose, aspartame and stevia. They wanted to check whether these products, which have become popular as an alternative to sugar in the midst of the battle to combat the obesity and diabetes epidemics, are or are not inert, if they have any effect on the body. And they did so by recruiting 120 healthy adults who were separated into four intervention groups and two control groups: all four were given sachets of saccharin, sucralose, aspartame, and stevia; to a control group, sachets with minimal doses of glucose, the same amount that the sachets of the four sweeteners usually have added; and the other control was given nothing. The researchers gave these substances for two weeks and studied potential changes in each participant’s microbiome and blood glucose levels.
The scientific community is divided, with studies that conclude that these sweeteners have no effect on the body and research that confirms the opposite. The findings of the research published in Cell turn the balance in favor of the scientific branch that finds effects on the organism: “Our results suggest that the intestinal microbes and the molecules they secrete were altered in the four consumer groups of non-nutritive sweeteners, each in its own way. These changes did not occur in the control groups. This means that [los edulcorantes analizados] they are not inert to the human microbiome”, specifies Eran Elinav, author of the study and researcher at the Weizmann Institute of Science. The impact was different depending on the type of sweetener, explains the scientist: “Regarding the glycemic effects, these were altered in the complete groups of humans that consumed saccharin and sucralose, but not in the complete groups that consumed stevia and aspartame. This suggests that the glycemic responses induced by saccharin and sucralose (possibly by the gut microbiome) may be more pronounced when assessed at the group level.”
The researchers also transferred fecal samples from the participants to sterile, germ-free mice that did not consume these sweeteners, to hone in on whether there was a causal link. “When we assessed the contribution of the microbiome to glycemic disturbances by fecal transplantation of gut microbes from consumers of best-response sweeteners [esto es, los que tuvieron cambios más consistentes en su microbioma], the mice developed glycemic abnormalities that largely mirror those of human consumers of all four sweeteners. And when we did the same experiment using samples from the bottom three responders [los que reportaron menos cambios en su microbioma], the mice that received the samples of the inferior responders to saccharin still developed glycemic alterations”, but not so the mice that received samples of the inferior responders of sucralose, aspartame and stevia, which “did not develop any glycemic alterations”. This means, Elinav points out, that the responses of the microbiome to the exposure of the sweeteners analyzed are “highly personalized”. “They can lead to glycemic disturbances in some but not all consumers, depending on their microbes and the sweeteners they consume.”
The study lasted just two weeks, but Elinav was “surprised by the speed with which the changes induced” by the sweeteners studied developed. Although he clarifies that some were reversible as soon as these sweeteners were no longer administered to the participants and more studies will be needed to delve into the long-term impact.
unknown health effects
The health effects of these changes in the microbiome or these alterations in glycemic tolerance remain to be seen. The researchers admit that more studies are needed to specify the impact on health, but from the outset, Elinav maintains, “the higher a glycemic tolerance test [la técnica empleada en el experimento para medir las alteraciones glucémicas], the more difficult it is for our body to process the sugar consumed, and this can lead people at risk to a risk of diabetes”. What the study makes clear, insists the researcher, is that these sweeteners “are not inert.” “In my opinion as a physician, once it has been pointed out that they are not inert to the human body, the burden of proof to prove or disprove their potential impacts on human health rests with those who promote their use, and we should not assume They are safe until proven otherwise. The long-term clinical implications of our findings warrant future non-industry-sponsored, randomized, interventional studies.”
The experts consulted outside the study have validated, despite the limitations, the findings of this research as proof that these sweeteners are not inert. It is “important”, points out the digestologist and former scientific president of the International Human Microbiome Consortium, Francisco Guarner, “because there is a lot of consumption of these products and there is the idea that they are inert, but they are not: they make changes in the intestinal microbiota and alter the way in which the body processes glucose levels”, he points out, although he considers that the doses administered are higher than those actually consumed by the general population. Guarner also doubts that the changes in glucose tolerance are caused by the alteration in the microbiota: “These milligrams of sweetener probably have no impact [en el microbioma] if the person, for example, follows a Mediterranean diet and does physical exercise”.
Duane Mellor, dietitian and professor at Aston University some limitations that prevent being conclusive with the long-term and general population impact of Elinav’s findings: “This study does not show a link between all non-nutritive sweeteners and higher levels long-term high blood glucose levels and does not provide any information on how people who normally consume sweeteners or people with type 1 or type 2 diabetes respond to non-nutritive sweeteners. Therefore, for some people, it is probably a better option and a more sustainable approach to use sweeteners as a stepping stone to reduce the amount of added sugar in foods and beverages, reduce their sugar intake, and still enjoy eating. what they eat and drink”, he exposes, in declarations to Science Media Center. Elinav admits that future studies will have to assess what the impact of these sweeteners is “in people with cardiometabolic diseases and other populations at risk.”
For Gemma Navarro, head of Dietetics and Nutrition at Hospital Sant Pau in Barcelona, the findings of the study, however, “confirm” what dieticians have been observing for a long time: “That these products do not help us take care of the intestinal microbiome. As nutritionists, we do not recommend substitution, but rather accustom the palate to not taking sweeteners. It is necessary to limit the consumption of sweeteners, both with sugar and with other artificial ones.
The debate, however, is still open. Experts ask not to panic and clarify that, for now, the European Food Safety Authority has validated these products as “safe”. The long-term impact remains to be known, how prolonged consumption affects time (here it was only two weeks) and if these findings are replicated in other populations. “This study does not indicate the need to change the average consumption habits of non-nutritive sweeteners”, values Sarah Coe, a scientist at the British Nutrition Foundation. “It is important that the science on the long-term effects of non-nutritive sweeteners continue to be reviewed, and further research with more long-term randomized controlled trials in humans is needed to investigate the potential effects of non-nutritive sweeteners on the gut microbiota. and how this relates to health outcomes and disease risk. Switching to foods with sweeteners (instead of sugar) continues to be a way for consumers to manage their daily calorie intake as part of achieving a healthier, more balanced diet,” Ella Coe said. Science Media Center.
Elinav insists, in any case, on the need to “create awareness” that non-nutritive sweeteners are not inert: “It is important to bear in mind that the clinical implications for health of the changes they can cause in humans remain unknown. unknown and deserve future long-term studies not funded by industry. In the meantime, we should continue to find solutions to our sweet tooth, avoiding sugar, which is clearly more damaging to our metabolic health. Water still seems to be the safest recommendation.”
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