Over and over, our health is being shown to be significantly impacted on by the health of our gut and as such, our food choices (Tomasello, 2016). Some foods assist with building a healthier microbiome, whilst others can have detrimental effects. Our diet can impact our gut in as far reaching ways as our mental health, body weight, risk of bowel cancer or development of autoimmune conditions. A western style diet seems to negatively impact our gut health (Myles, 2014). But why? And which foods can have a positive, and a negative impact on the complex environment in our gut.
The role of our gut bacteria
The gut resists bacteria through two barriers; the mechanical, and the immune barrier. Gut bacteria promote health in a variety of ways. Regulation of gut motility, production of vitamins, transforming bile acids, absorbing minerals, and activating and destroying toxins are all roles our healthy gut bacteria play. They also maintain resistance against colonization of unhealthy bacteria by competing for nutrients and attachment sites on the surface of the colon, whilst also helping with development of the immune system itself. Having the right types of bacteria impacts upon which health conditions may or may not develop. For example, gut bacteria play an important role in obesity; high fat diets alter composition of bacteria, indicating that obesity may be associated with decreased diversity and changes to composition of gut bacteria. Two types of microbes, firmicutes and bacteroides have been found to be related to body weight. The higher the ratio, the more likely obesity is present, or will occur. Further to this, carrying extra body weight means more inflammatory cytokines; gut bacteria can promote this, due to their ability to promote chronic inflammation. Another example is inflammatory bowel disease; it may be induced by interactions between gut bacteria, cytokine response or an abnormal immune response in susceptible individuals (Alexsandrova, 2017; Rios-Covian, 2016).
Impact of a Western Diet on Gut Health
Some foods have great gut health benefits, whilst others can negatively impact our microbiome. A western style diet seems to negatively impact the gut microbiota, particularly if it is low in fibre, high in fat, high in carbohydrate or rich in irritants to the gut, for example alcohol and artificial sweeteners (Myles, 2014).
Why? The Western diet is characterized by an over consumption and reduced variety of refined sugars, salt, and saturated fat. Reduced nutrient density, ease of access to poorer quality foods, reliance on processed convenience foods and reduced intake of whole foods means an increased intake of foods which provide less of the fuel our body, and in particular our microbiota requires to function optimally (Myles, 2014).
A Western style diet frequently does not contain enough fibre (Tomasello, 2016). This is supported by the fact that Australian adults do not consume enough fibre on a daily basis (McMillan, 2017). Low fibre intake, over consumption of calories, particularly those from saturated fats and refined carbohydrates increases the risk of gut inflammation, and reduces the production of short chain fatty acids from foods rich in microbiota accessible carbohydrates (Daien, 2017).
In particular, the low fibre, high fat western style diet discussed above seems to lead to disruption of healthy bacterial balance in the gut. This can lead to weakening of the lining of the gut, making it more accessible to pathogens, due to weakened structure. This can then result in tissue damage, and increased risk of development of the conditions discussed above (Myles, 2014).
Foods to eat more of
Funnily enough, the foods that we know to be great for other aspects of our health, such as heart health, blood sugar management and weight management, are also great for our gut health as well. Following a more plant based, Mediterranean style diet seems to have wonderful benefits to our health. This means more vegetables, wholegrains, legumes, nuts and seeds and less processed foods, meat and alcohol.
Increase consumption of fibre to at least 25 or 30g per day if you are female or male respectively, which includes 20g of resistant starch as part of this. These resistant starches make great prebiotic foods, that feed the healthy bacteria in your gut to promote healthier microbiota (Aune, 2014).
We know that an overabundance of calories and some macronutrients can increase gut inflammation. However, several micronutrients have the potential to modulate it. Vitamins such as vitamins A, C, E, and D, folic acid, beta carotene and trace elements such as zinc, selenium, manganese and iron may exude some benefit, however more research in the immunonutrition space is still required (Myles, 2014; Tomasello, 2016).
Beyond this, an anti-inflammatory dietary pattern has become popular in recent years as a method of improving health. Given the similarities to a Mediterranean diet, its focus is on adequate vegetable consumption and reduction in intake of processed foods, it makes sense that this may also help improve the health of our microbiota, and as such disease risk (Tomasello, 2016).
Hydration is important
Drinking enough water on a daily basis helps to improve gut health in a number of ways. Firstly, it helps to soften the stool, making waste easier to pass through. Secondly, water helps to flush our system, hydrate our cells and keep our various systems running smoothly. How much fluid do we need? Aim for approximately 35mL per kilogram of body weight, with most (if not all) of this from water for optimal results.
Following a Western style diet may have negative impacts on the health of our microbiome, and be involved in increased risk of development of a number of health conditions. Inclusion of less processed foods, and more plant based options can have a significantly positive impact on the health of our gut, and health in general.
Author: Chloe Mcleod, Accredited Practicing Dietitian, http://www.chloemcleod.com/
Aleksandrova, K, et.al, 2017, Diet, Gut Microbiome and Epigenetics: Emerging Links with Inflammatory Bowel Diseases and Prospects for Management and Prevention, Nutrients. 2017 Sep; 9(9): 962. Published online 2017 Aug 30. doi: 10.3390/nu9090962
Aune, D, et. Al, 2011, Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies, BMJ, 343: d6617., DOI: 10.1136/bmj.d6617
Daien, C.I, et.al, 2017, Detrimental Impact of Microbiota-Accessible Carbohydrate- Deprived Diet on Gut and Immune Homeostasis: An Overview, Frontiers in Immunology 2017; 8:548, doi: 10.3389/fimmu.2017.00548
McMillan, J, 2017, ‘Fibre and the gut microbiome: understanding the role of dietary fibre in gut health’, webinar for Dietitian Connection, Accessessed September 8th, 2017
Myles, I.A, 2014, Fast food fever: reviewing the impacts of the Western diet on immunity, Nutrition Journal, 13: 61.Published online 2014 Jun 17. doi: 10.1186/1475-2891-13-61
Rios-Covian, D, et.al, 2016, Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health, Front Microbiol. 2016; 7: 185., Published online 2016 Feb 17. doi: 10.3389/fmicb.2016.00185
Tomasello, G., et.al, 2016, Nutrition, oxidative stress and intestinal dysbiosis: Influence of diet on gut microbiota in inflammatory bowel diseases. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. Dec;160(4):461-466. doi: 10.5507/bp.2016.052. Epub 2016 Oct 26.