Synthetic food ingredient, cellulose gum, shifts the microbiota toward pro-inflammatory type. Digest
Highly processed foods often contain ingredients such as emulsifiers, thickening agents, and stabilizers that improve texture and extend shelf life, although many of these compounds lack extensive safety testing. Consumption of highly processed foods has increased dramatically in recent decades (now representing over 57 percent of daily calories), alongside rates of inflammatory bowel disease and metabolic syndrome. Researchers investigated the effects of synthetic emulsifiers in the diet of healthy adults and found alterations in the gut microbiota associated with inflammatory disease.
Carboxymethylcellulose, also known as cellulose gum, is a synthetic emulsifier (i.e., a compound that blends water and oil together) found in foods such as [fruit juices, processed dairy products, cooked fish products, breakfast cereals, and many other foods](fao.org/gsfaonline/additives/details.html?id=51). It was approved for use in food in the 1960s and determined to be safe because it is not absorbed in the digestive tract and is excreted in the feces mostly unchanged. However, recent evidence has shown a direct effect of emulsifiers on the gut microbiota that promotes inflammation and carcinogenesis. A more modern definition of safety that considers the effect of food additives on the health of the gut microbiota is needed.
The authors performed a randomized, double-bllind controlled-feeding study with 16 healthy adults during which participants consumed a Western style diet without emulsifiers or with carboxymethylcellulose added. All participants consumed an emulsifier-free diet prepared in a metabolic kitchen for three days and then were admitted to an inpatient facility for 11 days where they were randomly assigned to continue the emulsifier-free diet or switch to a diet supplemented with 15 grams of carboxymethylcellulose. Participants answered questionnaires about their normal diet and provided blood, urine, and fecal samples at multiple times over the 14 study days. Finally, the investigators performed a sigmoid colonoscopy and took biopsy samples in order to directly sample the microbiota and intestinal environment.
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Carboxymethylcellulose consumption was associated with a significant increase in after-meal abdominal pain but was not associated with increased inflammation, gut permeability (i.e., leakiness), appetite, food consumption, or bloating. Participants consuming carboxymethylcellulose experienced a greater shift in the population of bacteria in the microbiota over the study period, losing overall diversity and specific species such as Faecalibacterium prausnitzii, a producer of beneficial short-chain fatty acids. Within three days of initiating carboxymethylcellulose consumption, beneficial fecal compounds such as short-chain fatty acids and essential amino acids were depleted even though the population of bacteria had yet to change substantially.
The results support the growing concern over emulsifiers and other additives in processed foods and their effects on health.