Benoit Chassaing, Omry Koren, Julia K. Goodrich, Angela C. Poole, Shanthi Srinivasan, Ruth E. Ley, Andrew T. Gewirtz. Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature, 2015; DOI: 10.1038/nature14232
The same has not yet been studied in humans, however it seems likely that the findings will be replicated. The food additives studied were the emulsifiers added to foods to thicken, improve texture, and extend shelf stability.
It was found that these emulsifiers were able to alter the gut microbia (THINK: friendly bacteria) and promote intestinal inflammation. Intestinal inflammation is linked to the development of Inflammatory Bowel Disease and the metabolic syndrome (weight gain, central adiposity, insulin resistance that can result in diabetes, cardiovascular disease and fatty liver disease).
The researchers fed mice two very commonly used emulsifiers: polysorbate 80 and carboxymethylcellulose, at doses that were meant to mimic the consumption in processed foods. The emulsifier consumption changed the bacteria composition of the gut microbiota to more pro-inflammatory. The altered microbiota were able to colonize the intestine, such as in Small Intestine Bacterial Overgrowth (SIBO). Normally, the intestine is protected from its microbiota by mucus structures that cover the intestinal surface, therefore most of the bacteria are kept at a distance from epithelial cells that line the intestine. The emulsifiers were able to promote gut translocation, meaning the bacteria were able to reach the intestinal epithelial cells (basically eat through the mucous lining of the intestine), causing gut inflammation. In addition, the mice began to eat more, gain weight, and have more difficulty controlling their blood sugar, consistent with promotion of metabolic syndrome.
The bottom line: Inflammation is not good. Inflammation is linked with the development of chronic inflammatory disease and metabolic syndrome. Emulsifiers increased inflammation in the gut in mice. It is likely, but not yet proven, that similar findings would be replicated in humans. I wonder if other 'natural' emulsifying agents, such as soy lecithin, carregeenan and guar gum would do the same.
Take home: More reason to avoid processed foods and the additives associated with them! There is no "carboxymethylcellulose" in whole foods. Keep it clean!