Why Food Additives May Cause Gut Inflammation

melting ice cream cones
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Emulsifiers are a helpful group of food additives that are used to extend shelf life and keep ingredients from separating. But, according to new research from Georgia State University, emulsifiers could contribute to chronic gut inflammation and incidence of certain diseases associated with metabolic syndrome. Metabolic syndrome is a group of factors such as abdominal obesity that increase the risk for type 2 diabetes and cardiovascular disease; the condition became increasingly prevalent in the United States as obesity rates rose.

The researchers conducted animal experiments to test the effect of two emulsifiers, polysorbate 80 and carboxymethylcellulose, on the gut microbiota of mice. They found that germ-free mice with normal immune systems developed low-grade intestinal inflammation and became more prone to overeating at low doses of the emulsifiers. At high doses, germ-free mice developed both obesity and insulin resistance. Furthermore, the emulsifiers induced colitis, which is a chronic inflammation of the intestinal tract, in mice that were genetically predisposed to develop the condition. The authors of the study suspect that emulsifiers can break down intestinal mucus over time when consumed in large quantities, thereby lowering species diversity of the gut microbiota. Further animal studies and clinical trials will likely explore the relationship between food additives and specific bacterial species populations, contributing to an increased understanding of how this relationship functions in humans.

Emulsifiers are frequently found in highly processed foods such as ice cream, salad dressings, veggie burgers; the food additives are regulated by the U.S. Food and Drug Administration (FDA) and have been deemed safe for human consumption in the quantities typically found in processed foods. However, the authors of the study emphasize that past testing has focused on cancer promotion and acute toxicity, concluding that it has perhaps been inadequate in monitoring long-term health outcomes.

This conclusion calls into question the role of food safety testing for impacts on long-term outcomes such as metabolic syndrome to the same degree that cancer promotion potential is tested.  

Moreover, certain subsets of the population could be more susceptible than others to the effects of food additives. According to Andrew Gerwitz, a lead author on the study, “the idea that a subset of the population may be sensitive isn’t on the radar” for regulators. Creating a single set of dietary guidelines and food safety recommendations that apply for the majority of Americans can be a challenge for nutritionists and policymakers, and differing effects of food additives on gut microbiota highlight the complexity of the issue.

The authors emphasize that food additives are just one contributor to multifactorial diseases associated with metabolic syndrome—antibiotic overuse in livestock and lack of dietary fiber can also alter the gut microbiome in humans. Advocacy organizations such as AllergyKids Foundation and the Center for Food Safety monitor the food industry and are likely to scrutinize further research on emulsifiers and other food additives as the links become more clear.

The paper represents a recent explosion of interest in the microbiome, a relatively new area of nutrition science generating considerable interest in both the research community and the public eye. While the Georgia State study focused on food additives specifically, other studies are exploring the effects of phytochemicals, probiotics, and dietary supplements on gut microbiota. The Fourth Annual World Summit on Gut Microbiota for World Health will be held in Barcelona from March 14-15, 2015, with the goal of translating advances in gastroenterology to the medical community. According to Francisco Guarnar, chair of the scientific committee for the summit, “knowledge on the microbial communities that inhabit the human gut has grown exponentially during the last few years, and there is a profusion of novel information flowing from basic science laboratories into the clinical sceneries.”

Translating this scientific knowledge into basic recommendations for consumers can be a challenge. According to Gerwitz, “when it comes to people making their own decisions, between our studies and others out there, it’s better to eat less processed food.” Future research could impact policy not only through the FDA regulations, but also through dietary guidelines; the recent scientific report of the 2015 Dietary Guidelines Advisory Committee (DGAC) conducted an exploratory review of nutrition research on the role of the microbiome, but “did not find sufficient evidence to address this question in the 2015 report. However, the Committee considers the microbiome to be an emerging topic of potential importance to future DGACs.”

It’s possible that future dietary guidelines will incorporate research on gut microbiota to inform consumers about the potential effects of food additives and other substances in their diets. In the meantime, eating less processed foods and eating more plant-based diets that incorporate fresh ingredients may decrease consumption of food additives, such as emulsifiers. Eating less emulsifiers may promote healthy gut microbiota through inclusion of dietary fiber and probiotics, which can also improve consumers' overall health.

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