Inflammatory Bowel Diseases, the Microbiome and Sugar: Yet More on the Importance of Diet

Many times on this blog (look here and here, as just 2 examples), I’ve looked at research regarding the relationship of what is currently consumed as food in the industrialized world and its relationship to gut disease.  The increase in the rate of inflammatory bowel diseases in people – including children – is a story I’ve been following for awhile.  Research has focused in on diet to find answers because the rates of the disease in the industrialized world is far higher than in developing countries.  In the United States alone the number of people suffering from Crohn’s disease jumped from 2 million in 1999 to 3 million by 2015.  And historically, children did not get it:  now they do.

It’s already been established that a high-fat diet can trigger IBD, but the role of sugar has been more controversial.  In my past posts, I’ve pointed out that since the 1970s, the inclusion of high fructose corn syrup has increased 4 fold in our food supply.  And science has already correlated the consumption of sugary drinks and colorectal cancers, likely due, in large part, to alterations in the biome caused by the heavy consumption of sugar.  Thus, new research out of the University of Texas Southwestern Medical Center really caught my attention.  For 7 days these scientists fed mice a solution of water with a 10% concentration of different sugars:  glucose, fructose and sucrose.[i]  In those mice that were genetically predisposed to develop Crohn’s, or in those that were given a chemical to induce colitis, the symptoms were much more severe if they were first given sugar – or given sugar after the disease had started.

The scientists then analyzed the gut bacteria before and after the sugar.  They found that glucose, in particular, caused significant changes to the population of gut bacteria.  Bacteria which produce mucus-degrading enzymes like Akkermansia were found at higher levels while other probiotic species, like Lactobacillus, became less abundant.  (Bear in mind, Akkermansia often has probiotic properties.  (See here, for example.)  There are obviously many co-factors involved including, I am sure, amounts of bacteria.  That is – there is disease associated with low levels of Akkermansia,  as well as excessively high levels.  Balance is always key!)   However, in this case, high levels of the mucus-degrading bacteria caused the mucus layer that protects the lining of the intestines to thin. making it more prone to infection by other bacteria.  The high amounts of Akkermansia, and our old friend, Bacteroides fragilis (which also has good and bad sides – see here), increase the propensity for infection:  “Due to the erosion of the mucus layer, gut bacteria were in close proximity with the epithelial layer of the large intestine in glucose-treated mice…Breaking of the epithelial barrier is the key initiating event of intestinal inflammation.”[ii]

The final step of the experiment involved a fecal transplant from the sugar-fed mice to other mice…who then proceeded to develop worse Crohn’s, confirming that the gut bacteria are the cause. Also, the sugar did not exacerbate disease pathology in those animals who were either germ-free or given antibiotics, further confirming the relationship of inflammation and infection to the gut bacteria:  “Together, these data suggest that intake of simple sugars predisposes to colitis and enhances its pathogenesis via modulation of gut microbiota in mice.”  In future research, the scientists will look at how high sugar intake leads to other diseases including obesity, fatty liver and neurological disorders including Alzheimer’s.

Addendum:  As I was about to post this, I spotted a new article on Gut Microbiota for Health which summarized research into the relationship of food to the risk of developing Crohn’s.[iii]  Food groups were weighted based on their relationship to inflammatory markers in the blood, like c-reactive protein (CRP), TNF, IL-6.  Three large cohorts in the USA were used, which included  328 people with Crohn’s and 428 people with ulcerative colitis.  Answers on questionnaires were tallied into an index:  the higher the score, the more proinflammatory foods were consumed (processed and red meat, refined grains, sugary beverages, etc.) while the lower the score, the more anti-inflammatory foods were consumed, including vegetables, tea, coffee, etc.  The results:  “Dietary patterns with high inflammatory potential were associated with increased risk of Crohn’s disease, compared with participants who showed a high intake of foods with lower inflammatory potential.  The more “junk food” consumed, in fact, the great the risk for Crohn’s.  (Strangely, food intake seems unrelated to the development of ulcerative colitis.)

I just keep wondering when diet is going to become a first line treatment for inflammatory bowel diseases.


[i] S. Khan el al., “Dietary simple sugars alter microbial ecology in the gut and promote colitis in mice,” Science Translational Medicine (2020). … scitranslmed.aay6218



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