Fibre and anti-inflammation: The secrets of short chain fatty acids
We’re all told that we need to eat more fibre in our diet. Pick your reason – there are plenty out there. From heart disease to stroke, fibre is implicated as an important factor in combatting a number of health issues. But it’s fibre’s relationship to allergic disease that has excited Dr Alissa Cait, Postdoctoral Research Fellow at the Malaghan Institute of Medical Research, as it’s shown a remarkable ability to prevent asthma and allergy.
“It’s important when discussing anything about diet or fibre that we first talk about the microbiome,” Dr Cait says. “Much of the fibre we eat, primarily plant cell walls, we can’t digest. We don’t have the enzymes to break them down. That’s the job for the microbiome – the billions of bacteria living in our gut." The fibre passes through our stomach and small intestine, she says, and when it reaches the lower intestine, it’s fermented by the microbiome. The fermentation breaks the fibre down into lots of different molecules we call short chain fatty acids which we can now use.
“The short chain fatty acids are what’s really exciting,” Dr Cait says. “They have all kinds of effects on the body. For one, they make the intestines healthier as they’re an important food source for your colonic epithelial cells – the cells lining the walls of your intestines. Studies have shown that short chain fatty acids strengthen the walls of the gut and help keep their integrity.”
Gut permeability or ‘gut leakage’ is commonly associated with a range of autoimmune conditions. A leaky gut isn’t great at keeping undigested food ‘out’, and this permeation of molecules wreaks havoc with the immune system. Pre-clinical studies have shown that a high-fibre diet is associated with better barriers and a stronger gut lining.
However, it’s not just gut integrity where short chain fatty acids play an important role. Dr Cait has also discovered they hold potential for preventing allergic conditions, like asthma and food allergies.
“Byuterate is a common short chain fatty acid,” she says. "When it’s digested, it interacts with your immune system and turns on regulatory genetic pathways in affector T-cell. These T-cells then start producing chemical signals that interact with other cells in the immune system, telling them to stop producing inflammation. These short chain fatty acids are basically turning off the inflammatory immune response."
Dr Cait says there is a lot of data to support this. “Even a single, high-fibre meal can have anti-inflammatory effects. My research is currently looking at a bunch of different fibre sources and seeing what effect the short chain fatty acids generated have on different cells in the immune system.
“Hopefully, we’ll be able to identify certain fibre products that are beneficial for certain types of allergic or autoimmune responses.”
Dr Alissa Cait is a Postdoctoral Research Fellow at the Malaghan Institute of Medical Research.