Alcohol and your gut: disrupting the balance of good vs bad bacteria

Anxiety and stress can also have a profound effect on what comprises a delicate equilibrium

Unexplained digestive problems are common, even if we lead a healthy lifestyle, because the gut is a such a complex part of our body.

In fact, the gut may very well hold the key to unlocking answers about everything from depression to boosting our immunity, as the changes in our gut affect other aspects of our body.

The gut microbiota potentially consists of 2,000 species of bacteria and other microbes, with its evolution still being mapped by scientists. Producing hormones and digesting food the stomach has trouble with, the gut is very busy and is the key to understanding personalised nutrition. With connections between the health of the gut microbiota in certain conditions, it can play a role in irritable bowel syndrome and inflammatory bowel disease. Suppose the delicate balance of our intestinal flora is tilted too heavily towards unhealthy bacteria. In that case, it can have a considerable impact on our gut health and our overall health.

Alcohol can easily throw this gut microbiota off-balance, weakening the structure of the gut lining and disrupting the balance of good versus bad bacteria.


"Alcohol consumption has been associated with a negative effect on the 50 million-plus healthy bacteria in our colon, the so-called gut microbiota," says Prof Barbara Ryan, consultant gastroenterologist, the Hermitage Medical Clinic. "Chronic alcohol intake reduces the variety and number of different species of bacteria in our gut, which is detrimental to gut and overall health. It's not all bad news, however, as red wine in moderation (one to two standard measures per day and staying within safe drinking guidelines per week) has been shown to have a positive effect on the gut microbiota."

The reality is that alcohol has the potential to affect every part of our digestive system

We all tolerate alcohol in different ways due to the bacteria in our gut that helps to metabolise alcohol. This helpful bacterium breaks down alcohol, but increasingly we’re seeing the effects of excess alcohol consumption on people’s physical, mental, and gut health.

“The reality is that alcohol has the potential to affect every part of our digestive system and other parts of our bodies, too,” says Prof Ryan. “Women’s livers are 30 per cent smaller than men’s, which, in conjunction with a higher percentage of body fat, means that women are more sensitive to alcohol. Every gastroenterologist and liver specialist in the country has seen an increase in admissions of young women (in their 30s and 40s) with cirrhosis and liver failure, over the past five years, as women tend to develop cirrhosis at a younger age than men.”

Prof Ryan suggests the list of effects of alcohol on the digestive system is long; it can affect the gums and teeth, cause heartburn and gastro-oesophageal reflux disease, cause gastritis or ulcers and much more.

“It can damage the liver, causing cirrhosis but can also contribute to the development of fatty liver disease, the silent epidemic of this century [obesity and overweight also contribute to this],” she says. “Alcohol also contains “empty calories” which causes weight gain. If you have a gut condition like IBS, alcohol can trigger unpleasant gut symptoms like bloating and stomach cramps.

“Alcohol is also linked to an increased risk of a number of different cancers in both men and women. A study published in The Lancet Oncology in July estimated that even light-to-moderate alcohol consumption, which they classified as up to two drinks per day, was associated with an increased risk of breast, colon, and oral cancers, and that alcohol consumption contributed to the development of one in seven cancers worldwide. It’s also associated with an increased risk of a number of other cancers.”

The advice is that minimal alcohol is the best choice for our health. “If you do choose to drink alcohol” Prof Ryan recommends “it’s important to keep within the low-risk drinking guidelines [less than 17 standard drinks for men and less than 11 for women per week], to have a number of alcohol-free days each week and to avoid binge drinking.”

In somewhat the same manner, anxiety and stress can considerably affect our gut as it alters the balance of bacteria. The pandemic’s emotional, physical, and financial stress has caused us to cope and manage in different ways with varying stressors placed on us individually. All of this has had a knock-on effect on our gut and mental health.

It's like an information superhighway made up of a network of nerves

“There’s an incredible, well demonstrated connection between the gut and the brain, known as the gut-brain axis,” says Prof Ryan – who is co-founder of The Gut Experts – and strongly believes that an evidence-based approach to treating medical conditions must go hand in hand with a holistic approach especially in digestive conditions where the gut-brain axis plays such a big role in all gut conditions.

“It’s like an information superhighway made up of a network of nerves, the immune system and our hormonal system. There’s a constant and very complex flow of information between the gut and the brain, and studies have shown that what is happening in one can have an effect on the other. For example, if you’re happy, sad, anxious, or tired, this can all have a big effect on what’s happening in your gut. Who doesn’t recognise the feeling of ‘butterflies in your stomach’ or the need to dash to the bathroom when anxious – that’s your gut-brain axis kicking in.”

The gut microbiota (GM) is involved in this complex system. It’s often referred to as the gut-brain microbiome axis.

“The GM produces lots of substances – chemicals and hormones – that interact with our body and brain in hugely complex and poorly understood ways,” says Prof Ryan. “The GM produces chemicals such as tryptophan [a precursor of serotonin], dopamine and other substances, all important to our mental health. And numerous studies have shown a link between the GM and different mental health conditions like anxiety and depression.”

There’s now wide acceptance that a holistic approach is needed to manage gut symptoms and gut conditions, such as IBS, says Prof Ryan. “Anxiety and stress management through mindfulness, CBT [cognitive behavioural therapy], hypnotherapy, meditation, to name but a few, all play a role in helping to manage gut conditions,” she says. “Similarly, regular exercise [30 minutes, five times per week] through yoga or walking have all been shown to help patients with IBS.

“If you have IBS or functional dyspepsia, the effects of anxiety and stress on the gut are more pronounced because of the disordered communication between the gut and the brain. Taking proactive steps to manage stress and anxiety is particularly important if you have one of these conditions, but everyone can benefit from doing this.”