Hannah Phillips
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December 3, 2021

Alcohol and its impact on gastrointestinal health

As we head into the festive season after another massive year, we may find ourselves being surrounded by alcohol at social gatherings. While no one can be blamed for wanting to indulge and drown away the year or celebrate our achievements with family, friends and colleagues, an important consideration to make before consuming one-too-many drinks is what the alcohol you drink does to your body today and in the future.

Alcohol is absorbed and metabolised for elimination by the enzyme alcohol dehydrogenase found throughout the gastrointestinal system (Taylor et al., 2006, p. 172). Acetaldehyde is one of the breakdown products of alcohol that is toxic to the body and is associated with liver damage (Taylor et al., 2006, p. 172). Connections have been made between alcohol consumption and alcoholic liver disease, cancer, immune system dysregulation, pancreatitis, disruption of the circadian rhythm and heart disease (Engen et al., 2015, p. 223), with alcohol consumption reducing intestinal absorption of the fat-soluble vitamins A, D, E and K along with vitamin B12 and folate (Taylor et al., 2006, p. 172), potentially leading to nutrient deficiencies.

Chronic alcohol consumption is associated with nutritional deficiencies in fats, carbohydrates and protein due to malabsorption, which can present as increased intestinal fermentation of carbohydrates presenting as a FODMAP intolerance, and exacerbating IBS symptoms (Reding et al., 2013, p. 6). 

So how much is too much?

The Australian Government’s Department of Health recommends the consumption of a maximum of 10 standard drinks per week, with no more than 4 of those drinks consumed on a single day to minimise the risk of harm (Australian Government, Department of Health, 2020). Different alcoholic drinks have different percentages of alcohol in them, making it slightly more challenging for the consumer to know exactly how many standard drinks they are consuming. 

Moderate alcohol intake of 25g/day has been associated with an increased risk of liver cancer (Taylor et al., 2006, p. 174). Alcohol reduces and interferes with gastrointestinal motility (movement), increasing the risk of diarrhoea while binge drinking has been associated with an increase in irritable bowel syndrome (IBS) symptoms that may present chronically rather than when you consume alcohol (Reding et al., 2013, p. 5). 

How much alcohol is in my drink?

Wine and Champagne/sparkling wine

An average 150 mL glass of red wine from a restaurant contains 13.5% alcohol and equates to 1.6 standard drinks, whereas an average 150 mL glass of white wine contains 11.5% alcohol and is equivalent to 1.4 standard drinks. A full bottle of red wine contains 8 standard drinks, whereas a white wine bottle has less at 6.8 standard drinks (Australian Government, Department of Health, 2020). A glass of champagne containing 12% of alcohol is equal to 1.4 standard drinks, while the whole bottle is 7.1 standard drinks (Australian Government, Department of Health, 2020).


At the pub, you can expect your 285 mL pot glass of full-strength beer to contain 4.8% alcohol and equate to 1.1 standard drink, with mid-strength containing 3.5% alcohol and equating to 0.8 standard drinks and low strength beer being 2.7% alcohol and 0.6 standard drinks for the same volume of the drink (Australian Government, Department of Health, 2020).

A 375 mL bottle or can of full-strength beer contains 4.8% alcohol and is 1.4 standard drinks, a slab or case (24 cans or bottles) of full-strength beer is equivalent to 34 standard drinks (Australian Government, Department of Health, 2020).


A 30 mL glass of high strength spirits may contain up to 40% alcohol and is considered 1 standard drink, while a 700 mL bottle of 40% alcohol spirits contains 22 standard drinks (Australian Government, Department of Health, 2020).

It is a legal requirement for the alcohol percentage and number of standard drinks to be displayed on the bottle/can of alcohol, so get into the habit of checking the alcohol content and number of standard drinks you are consuming to ensure that you are aware of your consumption.

(NHMRC, n.d.)

Your microbiome and gut health

The microbiota or bacterial community within the gastrointestinal tract operates to obtain energy from food, forms a bacterial barrier from pathogens and can produce certain vitamins and amino acids (Engen et al., 2015, p. 223). Dysbiosis - an imbalance of bacteria in the gut - within the intestinal microbiota has been associated with inflammatory bowel disease, irritable bowel syndrome, coeliac disease, types 1 & 2 diabetes, cancer, cardiovascular disease, obesity and food allergies (Engen et al., 2015, p. 223). Alcohol consumption has been shown to disrupt the microbial balance within the gastrointestinal tract, in particular by reducing the phylum Bacteroidetes and Firmicutes populations allowing for an increase in the Proteobacteria population, which in turn can lead to small intestinal bacterial overgrowth (SIBO) (Engen et al., 2015, p. 225). Furthermore, dysbiosis due to alcohol consumption has been associated with intestinal hyperpermeability, or leaky gut, as a result of tight junction disruption measured through an increase in endotoxins, including lipopolysaccharides, within the bloodstream (Engen et al., 2015, p. 225) travelling to the liver and other tissues causing inflammation and potentially Alcoholic Liver Disease (Engen et al., 2015, p. 231).

Those with alcohol-dependency - with or without cirrhosis of the liver - have been found to have differing microbial populations. Alcoholics have a greater representation of Proteobacteria Firmicute and Gammaproteobacteria, Firmicutes Veillonellaceae and reduction in Firmicutes Lachnospira when compared to alcoholics with cirrhosis, suggesting a role in the microbiota composition in cirrhosis (Engen et al., 2015, p. 229).  

Are all alcohols the same?

Different alcohols have been shown to manipulate the gut microbtioa, with red wine increasing the presence of Proteobacteria, Fusobacteria, Firmicutes and Bacteroidetes and decreasing Clostridium. Bifidobacterium may provide prebiotic benefits to the gastrointestinal tract, making the consumption of the polyphenols in red wine beneficial for some (Engen et al., 2015, p. 231). Gin consumption decreases these same bacteria and increases Clostridium (Engen et al., 2015, p. 229). Clostridium has been associated with an increased risk of colonic cancer (Engen et al., 2015, p. 231). 

Animal studies and human trials have demonstrated that the use of the probiotic LGG alone, or concurrently with prebiotics or synbiotics, may attenuate and reverse dysbiosis, intestinal hyperpermeability, endotoxemia and liver damage (Engen et al., 2015, p. 233). However, as always, before embarking on a new supplement or probiotic regime, it is important to speak with a qualified nutritionist to ensure that the changes you implement will support your health.

Alcohol and mental health

Another important consideration is the impact alcohol has on our mood. Alcohol can make us feel uninhibited and may be associated with a reduction of tension (Awaworyi Churchill & Farrell, 2017, p. 86), however, alcohol is a depressant with a potential comorbid relationship with depression exacerbating depression with increased alcohol consumption as opposed to the frequency having a greater correlation with depression (Awaworyi Churchill & Farrell, 2017, pp. 86 & 90). 

While we know that alcohol can impact our health negatively when overconsumed, 1-2 standard drinks have been shown to have less of a detrimental impact on our health. So, this festive season, mindful and conscious consumption of alcohol is the best way forward to ensure that you don’t over-indulge. 


Australian Government, Department of Health. (2020). Australian Alcohol Guidelines Revised. Retrieved from https://www.health.gov.au/news/australian-alcohol-guidelines-revised 

Australian Government, Department of Health. (2020). Standard Drinks Guide. Retrieved from https://www.health.gov.au/health-topics/alcohol/about-alcohol/standard-drinks-guide 

Awaworyi Churchill, S., & Farrell, L. (2017). Alcohol and depression: Evidence from the 2014 health survey for England. Drug and Alcohol Dependence, 180(August), 86–92. https://doi.org/10.1016/j.drugalcdep.2017.08.006 

Engen, P. A., Green, S. J., Voigt, R. M., Forsyth, C. B., & Keshavarzian, A. (2015). The gastrointestinal microbiome: Alcohol effects on the composition of intestinal microbiota. Alcohol Research: Current Reviews, 37(2). 

NHMRC. (n.d.). Alcohol. Retrieved from: https://www.nhmrc.gov.au/health-advice/alcohol 

Reding, K. W., Cain, K. C., Jarrett, M. E., Eugenio, M. D., & Heitkemper, M. M. (2013). Relationship between patterns of alcohol consumption and gastrointestinal symptoms among patients with irritable bowel syndrome. American Journal of Gastroenterology, 108(2), 270–276. https://doi.org/10.1038/ajg.2012.414 

Taylor, B., Rehm, J., & Gmel, G. (2006). Moderate alcohol consumption and the gastrointestinal tract. Digestive Diseases, 23(3–4), 170–176. https://doi.org/10.1159/000090163 

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