I’ve been enjoying reading a review paper that writes all about what researchers know of the mucous layer in our intestines. Yes, I said enjoying, because it’s so exciting to read research that confirms the importance of things that I’m always talking about in clinic. (Like stress, cortisol and the impact they have on the intestinal mucous layer.) Like many things in our bodies, when we understand them more, we can see the brilliance of their design. The intestinal mucous layer is no different. Where it’s been thought of as just a lubricant to help your poop slide through your intestines comfortably and easily; research is helping us understand the importance of it and the co-dependence of the microbiome and the mucous layer.
The review is called “Fight them or feed them: how the intestinal mucous layer manages the gut microbiota” and is written by Bjoern Schroeder. You can find a full copy of it here: https://academic.oup.com/gastro/article/7/1/3/5305718
What is the mucous layer?
The mucous layer is a spectacularly amazing defense mechanism that our body has developed to cover the intestinal cells (epithelium) that keep the trillions of bacteria, yeasts and funghi that form our gut microbiota from entering our bloodstream and the rest of our body. The wall of our intestines is just one cell thick, which allows nutrients and metabolites to pass through easily, but can also mean that other less desirable allergens, toxins, or bacteria and their wastes can pass through and trigger an immune inflammatory response.
THE ELECTRIC FENCE
In the small intestine, the mucous is a thin layer that covers the finger-like projections (called villi) that cover the intestinal wall and help us absorb nutrients. The mucous layer here is loose so that nutrients and metabolites can pass through to the intestinal wall for absorption in to the blood stream.
“the small intestine is a metabolically active organ…specialised in nutrient uptake” (Schroeder, 2019, p. 4)
How cool is it that the mucous layer in the small intestine protects our body from bacteria moving in to the bloodstream by containing anti-microbial molecules? These molecules turn the mucous layer in to an electric fence. Um, awesome. (Geeking out over here!)
THICK and JUICY
So, in the large intestine, the mucous layer is thicker, with two distinct parts to it – the inner and outer. The inner layer has no bacteria in it. The outer layer has microbes and food particles in it as it doesn’t have a distinct end point, rather it sort of dissolves or blends into the open space in the intestines. The mucous layer in the large intestine doesn’t have anti-microbial molecules in it like the small intestine. Defence comes from molecules that bind bacteria together so they can’t move towards the intestinal wall and they’re too big to pass through the gaps or channels.
There are an estimated 100 trillion bacteria in our bodies, with much of this living in the large intestines (also called the colon). Whoa. The collection of all the different types of microbes is called the microbiota. You can find out a bit more about the microbiota and microbiome analysis here: https://akesohealthcare.com.au/services/microbiome-analysis/
“the colonic bacteria form an active internal bioreactor that produces a tremendous number of metabolites, including vitamins and short-chain fatty acids, which influence host physiology mostly in a beneficial way.” (Schroeder, 2019, p.4)
I love that description, it’s so visual, are you picturing those microbes beavering away in your intestines to keep you feeling energetic and enthusiastic? No wonder the microbiome and our gut is so important to our health. You can understand why it is important to keep this powerful, active reactor away from the intestinal wall where it could cross in to the blood stream and wreak havoc.
Now we’ve worked out that the intestinal mucous is designed to keep bacteria in its place and kill off any bacteria trying to pass through the mucous to the intestinal wall, you might be surprised to find out that the intestinal mucous needs bacteria to develop its full power. Specific bacteria in the microbiota help shape the health of the mucous layer by stimulating the production of mucous producing cells and influencing the types of carbohydrates in the mucous layer.
These bacteria break down fibres in food that our digestive enzymes can not. They ferment these, forming short-chain fatty acids that are used as an energy source by the bacteria but also fuel our intestinal cell’s function. A beautifully symbiotic relationship. There’s more to the story too, because some of the beneficial bacteria we host in our intestines need the mucous layer and its carbohydrates to fuel their energy production and growth.
Are you freaking out about now? Wondering WHAT THE HECK am I talking about? Will I ever get to the point? What’s the take home message? What do you need to do to look after your intestinal mucous and microbiome? (BTW, did you ever think you’d be so interested in mucous?!)
I do love to help people understand the physiology behind why you need to do or eat certain things, but OK, I’ll skip to the point:
EAT A FIBRE-RICH DIET
Yep, that’s it. Eat a fibre-rich diet to look after your intestinal mucous barrier. You’ll also look after you microbiome because those little critters love to ferment the fibre and make energy to grow and thrive.
Low-fibre, western style diets have been linked with altered mucous barrier function and the make-up of the microbiome. This impacts the whole body’s metabolism, including things like blood glucose levels, and is associated with IBS and auto-immune diseases like colitis. Whoa. A study of people with ulcerative colitis, self-limiting colitis and appendicitis found that they had a mucous layer that bacteria could penetrate. As the mucous layer decreased in thickness, disease severity increased for these people.
When we eat a low fibre diet, the mucous barrier gets broken down as bacteria eat the fibres (carbohydrates) in the mucous layer to meet their energy needs. Remember though that the mucous production and secretion is impacted by the type of bacteria that are present. In low fibre diets, the microbiome changes and there are less of the bacteria that encourage our intestinal cells to produce mucous. It’s a bit of a vicious cycle really.
Before you go start popping probiotics to fix the problem, know that modulating the microbiota and mucous production depends on having the right strain of microbe present. So it means you can’t just grab any probiotic with the right species (like Bifidobacterium or Lactobacillus), you need the right person for the job. The gut microbiome is complicated and the environmental factors impacting intestinal health (eg stress, diet, alcohol, lifestyle, chemicals in the home) need to be considered too.
The biggest factor in your gut health though, is what you eat, including how much fibre you consume.
DOn’t worry, you’ve got this
Research also shows that changes to the microbiome and mucous layer can be seen within 2 weeks. So don’t despair, it’s never too late to see the benefits of making changes to your diet. Full thickness of the mucous layer can be returned within 5 weeks.
So how much fibre?
Enjoy veges with every meal (total of about 6 cups/day when raw) and some nuts, seeds and fruit and you’ll easily reach (and pass) the current government recommendation of 30g/day for adults. Choose vegetables that are brightly coloured, and avoid the starchy ones to maximise fibre. (The exception to this is if they’ve been cooked and cooled, then they are a great source of resistant starch fibres that your microbiome loves!)
My fave fibre boosting food are seedy crackers, made with psyllium husks, flax and chia seeds. They’re a great vehicle for deliciousness like pate, guacamole or any other dip you like. ‘Tenina’s Seedy Crackers’ is the recipe I follow, you can find it here: https://tenina.com/recipes/nutty-seeded-crackers I’d love to hear about your fave way to boost fibre.
If you’d like to know more about the state of your microbiome and your gut health, then please get in touch and talk to me about microbiome analysis. It’s a novel way to accurately target what needs to be tweaked in your gut to optimise your health. If you have an auto-immune disease, allergies, asthma or eczema, then research demonstrates that you are likely to have imbalance in your intestines and microbiome that are contributing to your symptoms.