Researchers could find no evidence of a likely mechanism for a clinically relevant effect on gut microbiota commenting on reports correlating these effects as “studies where doses employed are beyond the possible expected intakes of humans”.
“There were existing significant study design issues that make conclusions of effects questionable, or where data were incorrectly evaluated or interpreted.”
Of importance to the industry is the UK and Canadian team’s findings concerning acesulfame K, aspartame,cyclamate, neotame, saccharin, sucralose and steviol glycoside, which are often used in a selection of commercially available sports supplements.
Sweeteners in the spotlight
The impact of consuming sweeteners on the gut microbiota received significant media attention as a 2014 study concluded that LNCS consumption influenced the composition and function of the gut microbiota, leading to enhanced risk of glucose intolerance.
Critics highlighted the study’s limitations in experimental design, analysis and reporting of the study data, bringing into question the conclusions drawn by the authors.
Evidence for the effects of both long-term and short-term diets on gut microbial composition and metabolism is plentiful.
A switch from a diet higher in calories/energy (i.e. higher in carbohydrate and/or fat) to those with lower caloric content (i.e. higher in protein and/or fibre) consistently resulted in a shift in gut microbiota make up specifically bacterial phyla and/or overall microbial diversity.
In the Calorie Control Council-supported review a literature search was conducted that yielded 17 publications as relevant primary research articles investigating LNCS on animals or humans’ gut microbiota.
Following review of these studies the team found a number of common critical issues when measuring the gut microbiome.
These included a lack of proper control groups, particularly isocaloric controls, choice of animal model and the use of LNCS doses that were greater than the currently established Acceptable Daily Intake (ADIs).
“In general, all LNCS also have a high sweetening potency, which means that dietary exposure will always be low - in milligram amounts - and well below the levels known to be needed by other dietary constituents to elicit a significant impact on the gut microbiome,” the review pointed out.
In conclusion, the research team emphasised highlighted data provided evidence of changes to microbiota numbers and phyla were likely the result of changes to nutrient intakes.
“The changes to the microbiota most likely result from differing outcomes of metabolic processing of these nutrients, resulting in different intracolonic metabolic by-products, possible changes in pH and osmotic character, and altered numbers and proportion of phyla,” the review added.
In addition, the team pointed out that laboratory animals had a very different microbiome from humans, so results were difficult to use in predicting a human response.
The team wanted to see studies that evaluate the impact of food additive/ingredient consumption on the microbiota to be conducted in relevant animal models or clinical populations at relevant exposure levels.
Controls needed to be built in to account for the presence of factors, including the habitual or background diet.
“The safety databases developed over decades for acesulfame K,aspartame, saccharin, sucralose, and steviol glycosides, which are structurally unrelated, indicate that these low or no-calorie sweeteners as a group, or individually, pose no safety concerns at their currently approved levels,” the review concluded.
In a statement, a spokesperson for the International Sweeteners Association (ISA) described the review as the "most thorough study to date examining the collective evidence about low calorie sweeteners and gut microbiota.
"The result is extremely significant in light of claims of negative effects on the microbiome based on non-human studies using extremely high levels of sweeteners and of the very low consumption levels of low calorie sweeteners in typical human diet.
"The sum of the data confirms the viewpoint supported by all the major international food safety and health regulatory authorities that low calorie sweeteners are safe at currently approved levels."
The Brussels-based organisation added that to the contrary, reports of effects on the microbiome primarily stem from animal or cell (in-vitro) experiments where the doses tested are beyond the possible expected intakes of humans.
"Moreover, there are large differences between the gut microbiome profile in laboratory animals and people, so translating data from animal studies to humans leads to biased and unsubstantiated claims."
Source: Food and Chemical Toxicology
Published online: doi.org/10.1016/j.fct.2018.12.005
“Assessing the in-vivo data on low/no-calorie sweeteners and the gut microbiota.”
Authors: Alexandra Lobach, Ashley Roberts, Ian Rowland