Food additives do not disrupt gut microbiome at real doses, lab study finds

Researchers are challenging the notion that food additives may harm the human gut microbiome, as people have commonly believed. None of the eight common food additives studied induced short-term gut dysbiosis nor impacted short-chain fatty acid production. 

Nutrition Insight speaks with paper co-author, professor Rajaraman Eri, who explains what has driven this misconception in earlier research: “In our published study, we used the so-called normal doses, reflecting real-world consumption levels. At that level, the responses are not that disruptive.”

“Science evolves over time. It is not a fixed set of absolute truths but a process that refines understanding as new evidence emerges. Earlier studies often used experimental conditions that differed substantially from real-life exposure, which may have shaped perceptions around additive safety.”

“At the same time, microbiome research is a rapidly developing field, and different study designs can produce different outcomes,” adds Eri, who is also the associate dean and head of the Biology Department at the Royal Melbourne Institute of Technology, Australia.

He says the team’s follow-up work in an animal model yielded contrasting results to previous research with unrealistic daily doses, underscoring the importance of context and the need for more research before broad conclusions can be made.

Preventing oversimplified findings

Eri points out that public discourse is not always nuanced, which can amplify people’s interpretations of preliminary research findings. This is why increasing scientific literacy among the public is essential to prevent oversimplification, while urging scientists to carefully communicate their study results and limitations.

In the Food and Chemical Toxicoloy study, the researchers collected fecal material from a healthy adult male human who ate a minimally processed diet with few food additives. Identified additive doses were ten times lower than the maximum permitted level.

The subject had not used antibiotics, prebiotics, or probiotics in the three months prior to the study. Researchers assessed the microbial community, alpha diversity, and the presence of probiotics or pathobionts (microorganisms) in the fecal sample, which was fermented in vitro. 

Researchers debunk food additive fears, as no dysbiosis was detected at real-world doses.The study’s limitations include sourcing data from a single fecal donor. The researchers caution their preliminary findings should not be generalized to the public and should be used to guide future research. 

Additionally, since individual gut microbiota may respond differently to additives, they plan to test whether their results can be replicated in vivo.

Support the microbiome with fiber

The researchers did not record any evidence of a “synergistic effect” when combining food additives. They analyzed microbial diversity after 48 hours of in vitro batch fermentation. Previous studies have never tested this.

“Our findings suggest that, under realistic exposure levels, the gut microbiota may tolerate certain additive combinations without measurable disruption. However, resilience likely varies between individuals,” notes Eri.

On whether this means the gut microbiome is more resilient than previously thought, he explains: “There is increasing recognition that microbiome responses depend on baseline composition, genetics, diet, and lifestyle.”

“While some degree of resilience appears plausible, we still need long-term and population-diverse studies to better understand these dynamics. Supporting gut health through established factors — such as adequate dietary fiber intake — remains a practical and evidence-based strategy.”

The researchers tested eight additives: polysorbate 80, iota-carrageenan, carboxymethyl cellulose, allura red, titanium dioxide, potassium sorbate, sodium metabisulfite, calcium propionate, and a combination of all additives.

Personalization on the horizon 

Eri points to the importance of accounting for intra-variability in fecal microbiota research, which involves analyzing the fluctuations or changes in fecal microbiota composition in an individual across time. 

Eri emphasizes realistic dosing and microbiome resilience for better science communication.Such differences in gut microbiota may lead to misleading results, or false positives, in experiments, note the researchers. For instance, random changes might mimic treatment effects. In the study, researchers had accounted for any false positives in their experiments but noted the microbiota could have been resilient to food-additive-induced dysbiosis.

“Intra-individual variability is an underappreciated aspect of microbiome research. The gut microbiota can fluctuate over time due to diet, stress, sleep, and other environmental factors.

Recognizing this variability encourages more careful study design, including repeated sampling and larger cohorts,” says Eri.

“It also highlights why translating microbiome findings into personalized interventions remains complex. We are likely still some years away from reliably tailoring interventions at an individual level, but understanding variability is an important step in that direction.”

Correct dosage and future development

According to the researchers, many studies use unrealistically high doses of additives in their experiments to test health effects, unlike their current paper. A previous review of animal studies flagged food additives like artificial colorants and sweeteners, emulsifiers, and antimicrobial preservatives as posing a risk to gut health.

Eri states: “Dose is fundamental in toxicology. As Paracelsus noted centuries ago, any substance can be harmful at sufficiently high levels.”

“By using exposure levels that reflect real-world consumption, our study aimed to provide results that are directly relevant to everyday dietary patterns. Findings derived from extremely high doses may be useful for mechanistic insight, but they do not always translate into practical health risk under typical consumption conditions.”

He adds that scientists or policymakers should focus on methodological refinement, especially to ensure realistic exposure models and minimize bias. 

“Transparent, well-controlled studies — independent of both commercial pressures and academic incentives for novelty — will strengthen confidence in findings.”

“At a population level, however, broader dietary patterns likely deserve greater attention. Established factors such as fiber intake, overall diet quality, and lifestyle behaviors have strong evidence supporting their impact on health outcomes. While additive safety should continue to be monitored carefully, focusing on well-substantiated determinants of health that may provide health benefits,” he concludes.