While it might seem obvious that gut microbiome is vital for digestion, its influence goes much further than dispatching your dinner. Nicknamed the second brain, gut bacteria can help keep skin, hormones, bone density, immunity, metabolism and mood in check.
Jane McClenaghan, a nutritionist at Vital Nutrition, explains: “Although found in our gut, our microbiome – a community of trillions of bacteria that live in your digestive tract – impacts every aspect of our health and wellbeing. If you look after your microbiome, it will look after your health.”
Unfortunately, there are many lifestyle factors which can disrupt the microbiome, from smoking to eating too much sugar, refined carbohydrates, alcohol, artificial sweeteners and ultra-processed foods. But even getting ill or taking pills and medicines on doctors’ orders can have a significant impact.
Dr Megan Rossi, The Gut Health Doctor explains: “Antibiotics not only kill the ‘bad’ bacteria, but the good guys can get caught in the crossfire too. Most research says antibiotics can impact our gut microbiome, and in some cases, particularly with multiple courses, the changes caused are irreversible, meaning that not all bacteria will come back after treatment.”
The impact of antibiotics on the gut is especially worrying for cancer patients. In 2019, a study followed almost 200 cancer patients in two NHS hospitals taking a type of immunotherapy called checkpoint inhibitors. It found patients who received broad-spectrum antibiotics for just a few days for common problems such as chest infections in the month leading up to starting treatment had significantly worse responses to their cancer treatment. Those who had taken antibiotics survived for a median of two months after immunotherapy, compared with 26 months in those who had not. The researchers from Imperial College London suggest the antibiotics may disrupt the balance of bacteria and microbes in the gut, which in turn impacts the immune system.
Dr David Pinato, from Imperial’s Department of Surgery and Cancer said: “Cancer immunotherapy can be successful in around 20 per cent of patients, but it’s very difficult to predict who is going to respond. This work adds further evidence that antibiotics have an impact. We have shown that with prior antibiotic exposure, patients’ response to immunotherapy and survival crashes.”
Last year, Stanford University’s school of medicine in California conducted a study which found that systemic antibiotic use could reduce survival rates for triple negative breast cancer patients.
Dr Simon Vincent, from UK charity Breast Cancer Now, explains the research: “Antibiotic use can potentially increase the risk of death from breast cancer by disrupting the gut microbiome and killing not only harmful bacteria but also beneficial bacteria that help regulate immune responses. This disruption can weaken the immune system, making it less effective at identifying and destroying cancer cells.
“However, antibiotics are often vital in the treatment of life-threatening infections and more research is needed.”
Elsewhere, academics at the University of Aberdeen and Queen’s University, Belfast, found a link between antibiotic use and increased risks of bowel cancer. Professor Leslie Samuel was involved in the study and warns: “We propose that antibiotic use, particularly early in life, can cause an alteration in the biodiversity of the bacteria that normally live in our large intestine, that leads to a pro-inflammatory state that increases the risk of developing bowel cancer. There has been a significant increase in antibiotic consumption in young children over a number of decades.”
Road to recovery: When it comes to rebuilding the microbiome, Dr Rossi says: “It’s not a case of starting from scratch after a course of medication, but it is extra important to feed the 40 trillion microbes living in your gut.
“Plant foods, such as vegetables, fruits, beans, seeds, nuts and wholegrains, contain the fibre your microbes love. The microbes in your gut feed on the fibre that is not digested in the small intestine and acts almost like a fertiliser. So, the greater the variety of plant foods we can feed our gut bacteria, every day, not just after a course of medication, the more diverse they become.”
In terms of recovery, more often than not our microbiome can return to its natural state eventually after antibiotics.
Adrienne Benjamin, Nutritionist at ProVen Biotics, explains: “It can take up to six months for the microbiome to rebalance in some people following a course of antibiotics and this can depend upon how often they have taken medications and the strength of the dose. We will all be impacted differently, so there may also be people whose gut microbiome takes longer to revert to its original composition and some who may experience ongoing gut symptoms.”
But if you want to give nature a helping hand, there are steps you can take. Jane says: “Generally speaking, foods that are good for our health – wholegrains and green leafy veg – also help the healthy bacteria in our gut thrive and survive, but there are supercharged foods which help it flourish.
“Fermented foods like kimchi, sauerkraut, kefir and kombucha are great for the gut, as they contain some of the probiotic bacteria that naturally inhabit our gut microbiome,” says Jane. “Start with a daily helping of live, natural yogurt, some olives or pickles.”
“Plant foods contain nutrients called polyphenols that help our good bacteria thrive. Polyphenols are abundant in colourful fruit and veg, herbs and spices, green tea, really dark chocolate and good quality coffee.”
As well as ensuring your diet contains the required fermented foods and getting enough sleep, probiotic supplements can bolster your microbiome – and you don’t need to wait until you’ve finished your treatment.
“There is good evidence to take the strain of bacteria known as lactobacillus rhamnosus GG (LGG) at a dose of 10 billion CFU twice daily during the antibiotic period, and for a week after,” says Dr Rossi.
“This strain demonstrated a reduced risk of antibiotic-associated diarrhoea which affects as many as one-third of patients.”
However, popping a prebiotic or probiotic isn’t a cure-all. Dr Rossi reminds us to be aware of our own needs.
“One study did suggest that taking the wrong strain delayed recovery, which reinforces the important concept that we shouldn’t just take any off the shelf as a one type fix all. Probiotics need to be indication-specific, meaning you need to take the right strain for the right condition for the right length of time.”
To be certain you are buying the right product, Dr Rossi advises: “Always do your research and consider these questions before making a purchase: What symptoms do I have and which strains of probiotic bacteria have been shown to improve this? What is the effective dose? How long does it take to see the benefit? Is there a reliable probiotic for this on the market? How does it need to be consumed?”
Exercise plays a key role in improving gut health too. Brisk walking, jogging, running or yoga can all help. Dr Rossi says: “Research shows that exercise can support the health of our gut microbiome. A study last year found that participation in moderate to high-intensity exercise for 30-90 minutes three times a week is likely to produce changes in the gut microbiota. Mindful movement practices like yoga have also been shown to improve overall digestive health.”
However you choose to move, there will be a benefit for your microbiome and as Jane adds, simply going outdoors helps. “Being in nature is one of the best things we can do for our microbiome, so exercise outside, get gardening or just take a walk in your local green space every day,” she says.
Evidence that your gut is recovering includes a better mood and more energy. Adrienne says: “Signs your gut health is improving include regular bowel movements with healthy, formed stools, little discomfort during bowel movements and fewer issues with bloating, gas, constipation and diarrhoea.”