Dietary fibre is an essential component in a healthy diet and is known for the favourable impact it has on colon health and digestive function. We’ve known this for decades yet there is often confusion as to whether we can get enough fibre on a LCHF template and when doing so, where our fibre comes from. This article is designed to set the record straight.
What is fibre?
Fibre is a portion of the carbohydrate in plants. Unlike other carbohydrates, it’s not broken down into digestible molecules which means it passes through to the large intestine relatively intact. There is strong clinical evidence suggesting higher intakes have a protective effect against cardiovascular disease, stroke, type 2 diabetes, breast cancer and colorectal cancer. It’s also associated with significantly lower weight and blood pressure.
For the sake of regular bowel motions and the above-mentioned benefits, we rely on fibre to do two things: resist fermentation in the small intestine, thereby adding content to the stool, and increase stool water content, leading to a stool that’s soft and easy to pass. There are certain types of fibres, each playing their role here.
Soluble fibre is found in foods including squash, sweet potato, parsnip, beetroots, turnip, psyllium, chia seeds, nuts and legumes. Soluble fibre attracts water, helping to form a gel like substance and in the process gathering the waste content in our large intestine to form a beautiful, soft, sausage like stool. Put simply, without soluble fibre your stool won’t form well, and it’ll be hard (literally) to pass. Another important element here is water – you can have all the fibre in the world, but without adequate amounts of water soluble fibre can ironically then contribute to constipation. Aim for 2 litres per day please.
We also love soluble fibre as it is fermented by bacteria in our large intestine creating short chain fatty acids (SCFA). These SCFAs have anti-inflammatory effects and actually go on to support the integrity of our digestive system.
Insoluble fibre is found in foods including seeds, dark green leafy vegetables, whole grains, onions, garlic, broccoli, cauliflower, Brussel sprouts, capsicum, sprouts and fruit & vegetable skins. Insoluble fibre (as the name suggests) isn’t water soluble and is poorly fermented in the large bowl. This means it remains relatively in-tact, adds bulk to the stool and in the process offers support in binding dead cells, bugs and bacteria so they can be eliminated via the stool.
The reality is that most plant foods contain a combination of both insoluble and soluble fibre and unless you are particularly reactive or currently treating IBS like symptoms, a combination of the two is required.
How much is required?
The evidence shows that an intake of between 25g – 30g of fibre per day is considered most protective, a figure also reflected in the Australian Dietary Guidelines and similar bodies in both the US and UK. The scary news is that individuals in the west are falling short of these recommendations by up to 10g per day – that’s 33%! The good news is that this gap can easily be filled by consuming an abundance of green leafy vegetables, nuts, seeds, legumes (if tolerated) and fruits.
What does 30g in one day look like?
When eating vegetables in the quantities recommended by The Natural Nutritionist (6 cups of non-starchy vegetables per day, please) there’s no way you’ll be low on fibre…
For example, a smoothie of ½ cup of raspberries, 1 banana, 100g of kale, 1 tablespoon of chia seeds, 1 tablespoon of tahini and 1 cup of almond milk contains approximately 18g of fibre. You can try our Mixed Berry & Tahini Smoothie recipe if you need inspiration. For something savoury, a buddha bowl containing your choice of protein, 100g of broccoli florets, 100g of kale, 100g of avocado and 100g of shaved carrot contains around 16.5 g of fibre.
But what about wheat bran and whole grains to ‘keep regular’?
Previously mentioned dietary guidelines suggest we need six serves of cereal and grain-based foods per day to achieve fibre intake and aid regular bowel movements. However, notice how easy it is to achieve more than half the daily goal (of 30g fibre) in just one LCHF meal, without one grain in site?
This leads to the often-asked question, which is “why does bowel regularity change when transitioning to an LCHF template?”. Studies have confirmed that the laxative effective of wheat bran (a whole grain) is actually due to the irritating effect of the undigested hull on the mucosa of the large bowel lining. It stimulates water and mucous secretion, aiding bowel movements. This is in comparison to finely ground wheat bran which lead to harder stools and reports of more uncomfortable bowel movements. This can in part explain why when starting a well-designed LCHF template a down regulation in bowel movements can be experienced. It doesn’t mean sluggish bowels forever, but that an allowance for transition is required as there was potentially a reliance on the irritating effect of grains.
The right LCHF template calls for an abundance of green leafy vegetables, nuts, seeds, some starchy vegetables, fruits and legumes. With this, there’s no way you’ll be short on fibre.
If you do react to seemingly healthy, fibrous containing vegetables then it could be a sign of dysbiosis in the large intestine or overgrowth in the small intestine. Low FODMAP diets and low intake of insoluble fibres may provide short term relief; however my recommendation is to initiate further investigation in these instances. In my opinion, long term restriction of healthful plant foods is never the solution.
If you need help in refining your LCHF template, testing or moving sluggish bowels please get in touch!
Reynolds A et al., 2019. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, 393, 10170, 434-445.
McRorie JW Jr & McKeown NM. 2017. Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber. The Journal of the Academy of Nutrition and Dietetics. 1117, 2, 251-264.
Wong JM et al., 2006. Colonic health: fermentation and short chain fatty acids. Journal of Clinical Gastroenterology. 40, 3, 235-43.
British Nutrition Foundation. Dietary Fibre. https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/dietary-fibre.html?start=2. Accessed 4 March 2019.
ATP Science. 2018. Fibre for Constipation and Diarrhoea. https://atpscience.com/fibre-for-constipation-and-diarrhoea/#_ednref8. Accessed 4 March 2019.