Fibre and the Gut

Fiber has anti-inflammatory activity, both locally in the intestine and systemically. In some ways, the anti-inflammatory action of fibre is in related to it’s ability to reduce obesity, which is known to induce a state of chronic inflammation.

But this isn’t the only way fibre reduces inflammation in the body. It’s thought that fibre indirectly affects the immune system via it’s ability to shape our intestinal community of microbes.

Studies have been done which test the effect of probiotics combined with fibre (synbiotics), but there is no convincing evidence that probiotics are more effective than fibre alone. When it comes to health gut flora, true star of the show is plant fibre.

The amount of fiber intake that meets the needs for 97–98% population (the recommended dietary allowance) is yet to be determined, and very little research and research has gone into the relative value and effect of different kinds of fibre.

Carbohydrates in general are an important source of energy (food) for intestinal microflora. The normal human diet contains various fibers and there are most likely some magical interactions (synergism) that occur between different kinds of fiber.

There are three main forms of dietary fibre: resistant starch, soluble fibre and insoluble fibre. In this post, we’ll explore the benefits of resistant starch, which is found in legumes, whole grains and potatoes. Cooking and cooling starches such as rice, pasta and potatoes raises the resistant starch content.

Resistant starch survives small intestinal enzymatic digestion intact, and travels on into the colon where it functions as a “prebiotic” (food) for healthy gut microbes in the large bowel. Prebiotics are carbohydrate compounds that stimulate good bacteria growth in the large intestine and colon. This improves our overall well-being and health.

Resistant starch is fermented (broken down) by our good bacteria, and this creates short chain fatty acids. SCFA’s lower the pH of the colon contents. This encourages the growth of beneficial bacteria while also making the bowel less hospitable to nasty pathogens and bad bacteria.

Resistant starch increases our absorption of important minerals like calcium and magnesium, decreases our absorption of toxic and carcinogenic compounds, improves insulin sesntivity, lowers overall blood glucose levels, and increases feeling of satiety (fullness).

Australians are eating less fibre, especially resistant starch, which may in part be why we are experiencing more gut problems, particularly pain, bloating and bowel disturbances. People most at risk of this reduced intake are those following the paleo/atkins movement, people avoiding potatoes because they are concerned about high GI, and people on gluten free or low FODMAP diets.

An expert panel on diet and bowel health conferred in Australia in 2011 and produced a report recommending an intake of 20g of resistance starch per day which is four times the current SAD (standard Australian diet) intake. A whole foods plant-based diet provides two to three times as much total dietary fibre as this, and as long as you are including whole grains, legumes and potatoes, a significant amount of this intake will be resistant starch.

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