Gut Health

The number of Australians with gut problems seems to have increased in recent years. Most of these individuals do not have Coeliac disease, proven food allergies or inflammatory bowel disease but suffer frequent abdominal pain, bloating and bowel disturbances. Emerging research is pulling together an understanding of the complex interaction between the gut, the food we eat and the role of the gut bacteria. We share with you some ideas on why there has been a rise in gut problems and offer some possible solutions.

Note: If you have persistent gut symptoms, please seek medical advice.

In recent years there has been a great deal of speculation about the pre-agricultural diet and what type of diet is best for the genetic heritage that evolution has given us. What we can tell you is that the humans have a herbivore type gut, very similar to that of apes and monkeys. The relatively smaller size of the human gut can be attributed to our long evolutionary history of cooking food, which reduces the digestive work required. More in Humans are Herbivores.

We evolved in tandem with our gut microbiome, the bacteria and other microbes that inhabit our gut. They are just as much a part of our digestive system as our own cells. They feed on dietary components that are not absorbed in the small intestine, such as dietary fibre and resistant starch. The microbiome pays its fare by providing us with energy and nutrients that would otherwise have been lost. The large bowel or colon is essentially a fermentation vat. This explains the gas.

We have all heard of “good bugs” and “bad bugs” thanks largely to the marketing of probiotic supplements. Recent medical research is finding links between the type of gut bacteria present and certain diseases such as Crohn’s disease. More recently Faecal Transplants have been successfully used to eradicate clostridium difficile infection. However, the current paradigm is still very much about putting the right kind of bacteria into the gut with little consideration of the type of growth medium, the food. This is like planting rice seeds in a wheat paddock with no irrigation and expecting to grow a crop of rice. “Good bugs” can only thrive and persist on the right food mix, the “pre-biotic”. A recent study (David et al 2014) found that it only takes three days of an all plant based diet vs an all animal product diet to produce a completely different balance of gut bacteria. More in Gut Microbiome.

Animal protein foods not only lead to a less favourable gut microbiome but their constituents can also damage the gut lining. Some of these such as saturated fat and endotoxins have a direct inflammatory effect while other such as methionine and carnitine produce inflammatory bacterial products. The loss of the bulking effect of dietary fibre further contributes to these effects. When the gut lining, which is only one cell thick, is damaged by this combination of “bad” gut microbiome and animal protein foods it loses it integrity and leaks like a sieve. Potential allergens and proteins that may trigger autoimmune disease are then able to pass into the blood stream. This state is known as “Leaky gut syndrome” and is thought by some to be responsible for many diseases including auto-immune diseases. Note the correct medical term for ‘leaky gut’ is ‘increased intestinal permeability’, a recognised feature of inflammatory bowel and coeliac disease. More in Leaky gut syndrome (under construction).

Dietary fibre is essential to gut health and is protective against other diseases such as heart disease, diabetes and breast cancer. Our page, Nutrient Density explains that adequate dietary fibre cannot be obtained by simply adding a supplement or particular food to an otherwise low fibre diet. Many gut problems are simply symptoms of inadequate dietary fibre. Constipation is not always apparent as one can have a transit time, from eating to elimination, of 5 days but still be “regular”. There is a group of NutritionFacts videos in the Resources section below which covers this in more detail. More in Fibre (under construction).

There is a group of carbohydrates known as FODMAPs which can ferment too quickly and produce large amounts of gas leading to abdominal pain and distension. A low FODMAP diet can often reduce these symptoms but may not be addressing the underlying cause of why the gut is so sensitive to gas. An inflamed gut lining, a “bad” mix of gut bugs and inadequate dietary fibre may be behind many FODMAP intolerances including whole wheat. Avoiding wheat, other whole grains, or even all starches, will reduce gas production and relieve symptoms for some people but it will not cure the unhealthy gut situation. In fact, the gut health is likely to be worse as fibre intake is further reduced and “good” gut bacteria are starved of fermentable carbohydrates. See FODMAPs.

Many individuals suffering from gut problems protest at the suggestion that their overall diet could be causing the problem. After all, they may be lean and healthy and following the advice of experts to eat more fish, chicken, yoghurt and olive oil, whilst restricting carbohydrates. What’s more, the gut problems may not have followed a change in diet. The onset of gut problems may be delayed for months or years following a change in diet or a habitual low starch diet. There may be a tipping point, an irreversible shift to one side of a precarious balance in an already stressed system that follows some event such a course of antibiotics (see Blaser 2011) or an episode of gastroenteritis. Once the gut bacteria and gut lining have gone past this tipping point they may not readily recover due to positive feedback mechanisms which maintain the new dysfunctional state.

A whole foods plant based diet is part of the solution for most gut problems. Having said this, we wish to make it clear that none of the information we provide is intended to be taken as medical advice and that persistent gut symptoms should be assessed by a qualified health practitioner. If you have Crohn’s disease, Diverticular disease or Ulcerative colitis you might find it interesting to look at the resources, including Success Stories on our page Inflammatory Bowel Disease – Ulcerative Colitis and Crohn’s Disease.

The transition to a whole foods plant based diet may be problematic for some. It can take several months to adapt to the higher dietary fibre content and greater bulk of whole plant foods. Focusing on increasing the intake of starchy foods (eg grains, potatoes) may be better tolerated than trying to eat large amounts of fruits and raw vegetables. The FODMAP information may assist in choosing a less gassy range of whole plant foods during this transition phase. Legumes, for example, may need to be introduced gradually – which may mean abandoning the standard plate model of a “protein” food comprising a quarter of the plate. There is plenty of protein in the food on the rest of the plate.

While there is no question that those with Coeliac disease must avoid all gluten containing grains, wheat, barley and rye, the evidence does not support the avoidance of wheat as a general health measure. Gluten free diets are associated with worse health outcomes (see Lebwohl et al 2017), probably because of the lack of whole grains. This need not be so as there are many other whole grains to choose from and no one is intolerant to all of them.

Plant-based practitioners often prescribe an elimination diet to treat flare ups of ulcerative colitis, Crohn’s disease and autoimmune diseases such as rheumatoid arthritis. A regular whole foods, plant-based diet may not be enough to bring severe gut inflammation under control. Elimination diets are also used to diagnose and treat suspected food intolerances that are not resolved by following a low fat, whole foods, plant-based diet. See our page on Elimination Diets.

Related pages:


Podcast & video interviews with gastroenterologists and other plant based practitioners:

There are many interesting resources about gut health on Dr Michael Greger’s NutritionFacts website. The peer-reviewed papers referred to in each video are listed under ‘Sources’ beneath the video. The blog posts link to relevant videos so they serve as a summary on the various topics. Here are a few of our favourite links:

Gluten, wheat & grains:

Peer reviewed articles

Success stories

Page created 5 October 2013
Page last updated 1 May 2019