What is the link between the gut, diet & health?

What is the gut microbiota?

Inhabiting the human body is the microbiome, a collection of 100+ trillion microbial cells.  A large number of these microbes reside in the gut, and are collectively referred to as the gut microbiota (1).  Whilst these microbial cells include bacteria, fungi and viruses, under the right conditions they have a mostly symbiotic relationship with our body.  In fact, emerging research indicates that the gut microbiota plays a very important role in many aspects of our health (2).

A healthy gut microbiota has a diverse and mostly balanced collection of microbial cells (1). The composition of an individual’s gut microbiota differs greatly from person to person and is influenced by many factors including age, environment, dietary habits, illness and medication.  Investigations into the gut microbiota indicate that stress, bad diet and drug intake can affect the number and diversity of gut bacteria, and negatively impact our health and well-being (3).

The human gut microbiota appears to be important in many diseases including:

  • Gut disorders (such as IBD, Crohn’s, Ulcerative Colitis and SIBO - Small Intestine Bacterial Overgrowth)
  • Metabolic and obesity-related diseases
  • Allergies and intolerances
  • Arthritis
  • Autoimmune diseases
  • Liver disease
  • Colorectal cancer
  • Depression
  • Inflammatory brain diseases (dementia, including Alzheimer’s)

New scientific insights indicate that the gut microbiota may become a therapeutic target through which to treat many of these notoriously difficult disorders and diseases (1).

What does good gut health mean?

  • Healthy gut microbiome  = balanced gut bacteria and a feeling of gut wellbeing
  • Absence of gastrointestinal symptoms of bloating, gas, pain, constipation and diarrhoea
  • No overgrowth of bad bacteria, yeast or parasites
  • Good absorption of nutrients
  • Good gut immunity = no food allergies or intolerances4.

How does diet affect the gut microbiota?

Research to date tells us that one of the key activities of the human gut microbiota is the fermentation of indigestible complex carbohydrates from the diet (1).  In short, when friendly gut bacteria in the colon ferment the indigestible fibre from these foods they produce short-chain fatty acids, which contribute to our daily energy, facilitate nutrient availability, promote gut health and importantly, aid immune function and resistance to illness and disease (1,5).

Eating a diet rich in fibre from fruit, vegetables and legumes appears increase short-chain fatty acids, enhance the gut microbiota fermentation process, and inhibit the initiation or progression of gut disorders (1,5).  In contrast, a diet that is based on highly processed foods and food additives can alter gut mucous allowing bad bacteria to invade the gut wall (also referred to as leaky gut) creating an inflammatory response, potentially impairing the body’s ability to resist infection and disease (4).

Tips to improve gut health

Which foods add healthy bacteria to the gut?

  • Dietary fibre from vegetables (particularly dark green and cruciferous vegetables), fruit and unrefined wholegrain foods including legumes and beans
  • Fermented foods such as kefir, sauerkraut, pickles and kombucha

*If possible consume fresh and organic food to avoid exposure to high levels of pesticides.

How to reduce inflammation and improve gut health?

  • Reduce or cut-out sugar intake
  • Reduce highly processed foods including (high GI) carbohydrates, which are pro-inflammatory and add to glucose overload
  • Reduce or limit acidic foods including meat, coffee, dairy and alcohol.

Can prebiotic foods and probiotic supplements help improve gut health?

Potential therapies aimed at improving gut health include both prebiotic foods and probiotic supplements.  There is evidence that they do confer health benefits1, but with some limitations.   

Prebiotic foods* include indigestible carbohydrates, which enhance gut microbe fermentation.  Prebiotic foods include (but are not limited to):

  • Garlic
  • Onion
  • Asparagus
  • Artichoke (particularly Jerusalem)
  • Leeks
  • Cacao
  • Oats/barley
  • Legumes (chickpeas, lentils, beans)
  • Apple
  • Banana

* Individuals with IBS, GERD or other gut disorders may have limited tolerance for certain forms of fibre, including some prebiotic foods.  It is recommended that they seek personalised advice from a qualified Nutritionist/Dietitian or their healthcare professional to manage any food intolerances.

Probiotic supplements are now widely available commercially.  However, they generally do not contain enough active bacteria, or are not specific enough to effectively deal with a particular health condition or disorder.  Nevertheless, many of the high quality probiotic supplements contain a wide range of bacteria strains, which is good for overall general health (4).

Julie Howell | Consulting Nutritionist
Latrobe Terrace Chiropractic


1.     Marchesi JR, Adams DH, Fava F, et al.  The gut microbiota and host health: a new clinical frontier. Gut 2016; 65:330-339 doi: 10.1136/gutjnl-2015-309990.
2.     Volkmann, ER. Intestinal Microbiome in Scleroderma. Recent Progress. Curr Opin Rheumatol. 2017; 29(6):553-560.
3.     Ursell LK, Metcalf JL, Wegener Parfrey L, et al. Defining the Human Microbiome. Nutr Rev. 2012 August; 70 (Suppl 1): S38-S44 doi: 10.1111/j.1753-4887.2012.00493.x
4.     Dr Shirley McIlvenny. Food Coach Institute Webinar series – ‘The 5 Things You Need to Know About Great Gut Health.'  Available from: http://www.iahnc.com/smart Accessed on 7 June, 2017.
5.     McOrist AL, Miller RB, Bird AR, et al. Fecal butyrate levels vary widely among individuals bur are usually increased by a diet high in resistant starch. J Nutr. 2011 May;141(5):883-9 doi: 10.39545/jn.110. Epub 2011 Mar 23.