Low fiber diets could harm gut microbiome

bowl of saladI was recently drawn to an article in The Atlantic (online) titled “Low-Fiber Diets Cause Waves of Extinction in the Gut.”

This article caught my attention for two main reasons: 1) Many of my patients with IBD are following low fiber diets, and 2) Diversity is key when it comes to our microbiome, so the word “extinction” scares me.

Fiber is an undigested carbohydrate in the sense that humans do not have the necessary tools to break it down. Therefore it’s available to nourish the trillions of microbes in our intestines. Many of us are familiar with the sometimes embarrassing gas that results from our gut bacteria feeding on fiber, but what’s less obvious are the healthy by-products of their feeding frenzies, including chemicals that help fight inflammation.

A microbiologist from Stanford University conducted a recent experiment on mice to study how a low fiber diet might affect the variety of the gut microbes. To do this, he and his team colonized germ-free mice with the same collections of gut bacteria. All of the mice were then fed a high-fiber diet before randomly converting half of them to a low fiber diet for seven weeks.

As one might expect, the low fiber diet caused a drastic decrease in the variety of microbial species (not ideal). What was less expected is that some species remained low even after returning to a high fiber diet. What’s more is that low-fiber mice gave birth to offspring with less gut microbial diversity (again, not ideal), and it became more and more difficult to reverse these changes in future generations.

Their findings support what other studies have shown in humans. The gut microbiomes of Westerners, for example, are much less diverse than rural Africans who traditionally eat a very high fiber diet.

Note that people with IBD are already shown to have a less diverse microbiome than those without the disease, and the frequently recommended low fiber diet isn’t helping rectify the situation.

Fortunately, many people with IBD can consume fruits, vegetables and other plant foods in their whole state when they’re healthy and not at risk of obstructing. Just because someone has IBD does not mean that they can never eat fibrous foods. Even people with active disease can often tolerate fiber provided it’s soft, such as in soups or smoothies.

I highly recommend that everyone with IBD work with a registered dietitian who specializes in gastrointestinal health and is very familiar with nutrition’s role in managing IBD.

In the meantime, keep reading my blog for more information.

DISCLAIMER: This information is for educational purposes only and is not intended as medical advice. Talk with your healthcare provider about any questions you may have related to your condition or your treatment plan.

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