AURORA, COLO. – Dietary additives lurking in processed foods may contribute to the development or exacerbation of inflammatory bowel disease (IBD), a leading gastroenterologist contends.
At the annual Crohn’s & Colitis Congress®, a partnership of the Crohn’s & Colitis Foundation and the American Gastroenterological Association, James D. Lewis, MD, MSCE, AGAF, of the University of Pennsylvania in Philadelphia, highlighted research from both animal and human studies pointing to certain widely used food additives such as carboxymethycellulose (CMC), polysorbate 80, and carrageenan as potential instigators in gastrointestinal inflammation.
“Extrapolating from mice to men, I think we can say that dietary additives may contribute to the etiology or perpetuation of IBD, but not all additives are the same,” he said.
Some additives appear to have deleterious effects on intestinal microbiota, while others may exert their baleful influence through mechanisms such as endoplasmic stress.
“It looks like some people might be a little more sensitive to additives than others, and if you were going to use any of this [research] to try and give some advice, maybe we would say that patients or first-degree relatives of people with IBD may want to avoid foods that contain high levels of additives, and if for no other reason, mothers or people with a family history of IBD might be encouraged to breastfeed to avoid early exposure to additives that are in infant formulas,” he advised.
Processed foods defined
The typical American diet may include a large proportion of processed foods, defined as “foods that have undergone biological, chemical, or physical process to improve texture, taste, or shelf life.”
Processed foods tend to be higher in fats, added sugars, and salts, and lower in fiber and intrinsic vitamins than minimally processed foods.
There is also a category of “ultraprocessed” foods, which contain little or no whole foods but are high in energy density. Many of these super(bad) foods are staples of the American diet, such as chips, hot dogs, chicken nuggets, breakfast cereal, soda, candy, and margarine. These and similar foods contribute from 25% to 50% of daily energy intake in the United States and Canada, Dr. Lewis said.
And North America is not alone, he added, pointing to a 2015 study showing that the consumption of ultraprocessed foods in Sweden increased “dramatically” from 1960 through 2010, and that this increase mirrored an increase in obesity prevalence in that nation.
Emulsifiers and thickeners
Dr. Lewis focused on emulsifiers and thickeners that are commonly added to processed foods and are, according to the Food and Drug Administration, “generally recognized as safe.”
Emulsifiers are “detergent-like molecules that stabilize mixtures of immiscible [nonhomegenous] liquids.”
Thickeners are additives that increase the viscosity of liquids without otherwise substantially changing their other properties.
In addition to the aforementioned products, other common additives include xanthan gum (a polysaccharide used as an emulsifier in salad dressings, baked goods, ice cream, and gluten-free products), maltodextrin (a sugar substitute marketed as “Splenda”), and soy lecithin (a soy derivative used as an emulsifier, stabilizer, and wetting agent).
Evidence of harm
Dr. Lewis noted that in 2013, investigators at the University of Liverpool, England, published a hypothesis suggesting that consumption of emulsifiers in processed foods may promote Crohn’s disease by increasing bacterial translocation. Their hypothesis was based in part on evidence that “very small concentrations of the emulsifier polysorbate 80 enhance bacterial translocation across intestinal epithelia. Undigested emulsifiers may increase bacterial translocation, particularly in the small intestine where the mucus layer is discontinuous. “
The authors also suggested that their hypothesis could be tested in clinical trials comparing enteral feeding with and without emulsifiers.
Other suggestive if not definitive evidence of a potential link between additives and IBD are data showing that IBD is very rare in young children.
“In your early stages of your life, you’re not consuming a lot of ultraprocessed foods. Indeed, the rate of intake of at least fast foods, which you can think of almost as a surrogate for ultraprocessed foods, goes up dramatically when people get to their teens, and this is the same time as we see, really, the big uptick in the incidence of IBD,” Dr. Lewis said.
A link between ultraprocessed food consumption and later development of IBD, primarily Crohn’s disease, is also suggested by data from the Nurses Health Study I and II and Health Professionals Follow-Up study. Among 245,112 participants with about 5.5 million person-years of follow-up, the highest vs. lowest quartile of consumption of ultraprocessed foods was associated with a 70% increase in risk for developing Crohn’s (hazard ratio 1.70, P = .0008).
Animal studies
Evidence for a possible mechanism whereby emulsifiers and thickeners cause intestinal changes comes from a study published in Nature in 2015 showing that adding CMC and PS80 to the drinking water of mice resulted in major shifts in the gut microbiota in both wild-type and interleukin 10 knockout mice, a model for IBD.
When the additives were put into the water the mice had a thinning of the mucus layer, allowing bacteria in closer proximity to the epithelium.
“When you put these into the drinking water of IL-10 knockout mice that are already predisposed to developing colitis, they were far more likely to go on to develop colitis over the course of 3 months,” Dr. Lewis said.
From mouse to man
Dr. Lewis briefly summarized results of the FRESH study that he and colleagues recently published in Gastronterology. In this trial, 16 healthy adult volunteers who agreed to stay and eat all meals at the research center were randomized to receive either an emulsifier-free diet or the identical diet enriched with 15 g of CMC daily for 11 days.
“I will comment that that’s a lot of carboxymethycellulose,” Dr. Lewis said.
The volunteers fed the CMC-enriched diet had a slight increase in abdominal discomfort after eating and a reduction in species diversity in the gut microbiota. In addition, these participants had reductions in levels of short-chain fatty acids and free amino acids, both of which are signs of a health gut environment.
“Furthermore, we identified 2 subjects consuming CMC who exhibited increased microbiota encroachment into the normally sterile inner mucus layer, a central feature of gut inflammation, as well as stark alterations in microbiota composition,” the investigators wrote.
Dr. Lewis cited a separate small study by investigators at the University of Illinois at Chicago and the University of Chicago. These investigators randomized patients with UC in remission to take supplements containing carrageenan – a seaweed-derived food additive that has been shown to cause inflammation in both in vitro and animal models – or placebo . The amount of carrageenan in the capsules was less than that found in an average daily Western diet, the authors noted.
The participants were followed with telephone calls every 2 weeks or until relapse, which was defined as an increase of 2 or more points on the Simple Clinical Colitis Activity Index (SCCAI) and intensification of treatment for UC.
Of the 12 patients who completed the study, 3 in the carrageenan group experienced relapses, compared with none of the patients in the placebo group (P = .046). The relapse occurred at 5, 32, and 42 weeks of follow-up.
Exceptions to the rule
“It’s not clear that all additives are harmful,” Dr. Lewis said, pointing to a placebo-controlled study suggesting a beneficial effect of soy lecithin in patients with UC. The additive is composed of at least 30% of phosphatidycholine, a component of intestinal mucus.
He also noted that there is an ongoing randomized, placebo-controlled trial comparing a low-additive diet to a habitual diet in 154 patients with mildly active, stable Crohn’s disease.
Session moderator Michael J. Rosen, MD, MSCI, a pediatric gastroenterologist at Stanford University Medical Center in Palo Alto, Calif., told this news organization that dietary components do appear to have an influence on the disease course in patients with IBD.
“I do think there are patients with IBD who are maybe genetically predisposed to being sensitive to certain components of diet,” he said in an interview seeking objective commentary.
“Particularly in pediatrics there are lines of evidence of diets maybe having some efficacy in treatment. It needs further study, but one commonality about those diets is that they tend to eliminate processed foods and focus on whole foods,” he said.
Dr. Lewis’ work is supported by grants from the National Institutes of Health, and from AbbVie, Takeda, Janssen, and Nestlé Health Science. He has served as a consultant to and data safety monitoring board member for several entitities. Dr. Rosen reported no conflicts of interest to disclose.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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