Dr Megan Rossi, internationally renowned gut health specialist, was interviewed by Dr Victoria Sampson ahead of the GBT Summit London 2025 in October, where she will discuss the microbiome and its implications for dentistry.
Founder of The Gut Health Doctor and The Gut Health Clinic in London and Manchester, Dr Megan Rossi (PhD, RD) leads a team of specialist dieticians translating cutting-edge science into everyday health. Passionate about tackling myths and empowering patients, Megan’s mission is to transform gut health worldwide by making evidence-based science accessible to all.
Dr Victoria Sampson is an award-winning functional dentist and researcher, known for her work in salivary diagnostics and oral microbiome testing. She co-founded The Health Society in London, pioneering a multidisciplinary approach to connect oral health with overall wellness.
Victoria Sampson (VS): You’re headlining the GBT Summit with a keynote on the oral-gut microbiome connection. Why is this topic so important right now, particularly for dental professionals?
Megan Rossi (MR): The latest clinical research is showing just how vital the oral microbiome is, not only as the gateway to our nine-metre digestive tract, but also to the systemic health of patients. From uncovering the missing link between diet and its cardioprotective effects, to its role in shaping dietary preferences and offering diagnostic potential for certain diseases, the oral microbiome is fast becoming a hot topic and is predicted to become an integral part of dental examination.
VS: What first sparked your interest in the microbiome, and has anything surprised you on the journey so far, particularly in relation to oral health?
MR: Back in 2010, while working as a clinical dietitian both in the hospital setting and in private practice with Olympic athletes, I noticed a common thread that sparked my curiosity in the gut. The lack of answers in the scientific literature led me to pursue my PhD in gut health.
It was during this time that I realised just how much I could help to improve people’s lives, in very real but often surprising ways, via this landmark scientific discovery. At that point, I knew I wanted to dedicate my career to gut health.
One particularly surprising factor has been the oral microbiome’s role in influencing blood pressure regulation, an issue faced by around one in three UK adults. Oral health can influence how effectively the body converts dietary nitrates (eg from beetroot) into nitric oxide, a compound that helps relax blood vessels and lower blood pressure. However, this mechanism can be overridden by certain dental interventions, such as the overuse of antiseptic mouthwash, which may, in turn, contribute to an elevation in blood pressure.
VS: For those in the dental world who may not be as familiar with microbiome science, how would you describe the connection between oral and gut health in everyday terms?
MR: Think of the mouth as the front door to a nine-metre-long tunnel, the gut. Every day, food, microbes and chemicals come through that door. Most are harmless, many are beneficial and a few can be troublemakers. Like all doors, they open both ways, meaning the oral microbiome influences the digestive tract and, in turn, the digestive tract can influence oral health. This connection explains why healthy gums and a balanced oral microbiome can help protect not only your teeth but also your digestion and overall health.
VS: What does the latest research suggest about how imbalances in the oral microbiome might contribute to wider health issues, or vice versa?
MR: The most convincing associations with an imbalanced oral microbiome and wider health include cardiovascular disease, with evidence showing higher risks of heart attack, stroke and atherosclerosis. There’s also a two-way relationship with diabetes, where gum disease can make blood sugar control more difficult and, in turn, diabetes can worsen periodontal problems.
Imbalances have been connected to adverse pregnancy outcomes such as preterm birth and low birth weight, and even to respiratory conditions, where aspiration of oral bacteria may play a role in pneumonia or COPD flare-ups.
Research has also highlighted associations with autoimmune conditions like rheumatoid arthritis, particularly involving Porphyromonas gingivalis, and with certain cancers, including colorectal and pancreatic, through mechanisms such as chronic inflammation and bacterial translocation.
These findings reinforce that an imbalanced oral microbiome is far more than a dental problem, as once thought.
VS: Are there any common myths or misunderstandings about gut health that you find yourself regularly addressing, particularly ones that might impact how clinicians support their patients?
MR: Yes, firstly that we should all take a probiotic for good gut health. Not all probiotics are created equal. Even if a product claims to contain billions of live bacteria, is ‘proven to survive’, or to use a ‘unique’ capsule technology, most probiotics on the market are not only ineffective but may exacerbate, or even cause, symptoms like bloating.
That said, when used correctly, the right probiotic can absolutely serve a purpose and prove beneficial, including within dentistry. The key is selecting the right strain (type of bacteria), at the right time (eg when you’re on antibiotics), in the right way (eg dose).
For example, the World Gastroenterology Organisation (WGO) guidelines on probiotics give the highest level of evidence (level 1) to recommending the strain Lactobacillus rhamnosus GG (LGG) at a dose of 10 billion twice per day, alongside antibiotic therapy, to help protect the digestive system (reducing incidence of antibiotic-associated diarrhoea by 70% compared to placebo).
‘More confused than empowered’
Then there is the idea that juice detoxes are good for gut health.Your body doesn’t need juice cleanses to ‘detox’. It already has highly effective detox systems in place, including the liver, kidneys and colon. In fact, research shows that juice diets can promote a pro-inflammatory oral microbiome profile, which can be harmful rather than helpful.
As for the concept that everyone should take a microbiome test to know their gut health, although we test the microbiome in clinical trials, most direct-to-consumer microbiome tests are not clinically validated. They can tell you some of the bacteria that are present, but they don’t give you the whole picture, nor what those microbes are actually doing. This explains why we don’t yet have enough evidence to translate the results into actionable health advice. In many cases, they can leave people feeling more confused than empowered.
VS: From a practical standpoint, how can dental teams support microbiome health in the advice they give patients? What should they be looking out for during appointments?
MR: There are a few really simple ways dental teams can make a difference. For example, when prescribing antibiotics, it’s worth considering probiotics too, and following the WGO guidelines so you’re recommending the right strains and doses to protect the gut.
It can also help to weave in brief conversations about diet, particularly with patients who have gum weakness or ongoing infections, because nutrition plays such a key role in both oral and gut microbiome health.
And finally, a thorough medical history check is invaluable. Conditions like cardiovascular disease, diabetes, pregnancy, respiratory disease, rheumatoid arthritis and even some cancers are all connected with oral health, so spotting these links early can guide much more tailored advice.
VS: You often speak about the role of diet in supporting gut health. Can you tell us a bit more about the ‘super six’ and the 30-plant challenge, and how they might support oral health too?
MR: When it comes to plants, aim to eat lots of variety across all six different plant groups: vegetables, fruits, wholegrains, legumes (beans and pulses), nuts and seeds, and herbs and spices – I call them the ‘super six’.
Each group, and the plants that shape them, provides a unique collection of different nutrients, gut-loving fibre, and plant chemicals (aka phytochemicals), many of which we can’t get from supplements.
This explains why cutting entire groups (eg keto or paleo diets) may leave your gut microbes worse off. Researchers from the University of Bergen found that eating a diverse variety of plants across these super six can add up to a decade of healthy years to your life. And it’s never too late to start; even an 80-year-old could live an extra 3.4 years by making the switch.
You may have heard about the concept of a 30-plant challenge, which encourages eating more than 30 different plant-based foods per week (but the sky is the limit; you don’t need to stop at 30). Studies, including The American Gut Project, demonstrated that those who ate more than 30 different plant-based foods a week had more diverse gut microbes (a key marker of gut health) than people who ate 10 or fewer, even if those who ate 10 ate more plants overall.
‘The benefits of plant diversity extend to oral health’
With so much more to learn in this cutting-edge area of research, my team at King’s College London is currently undertaking a randomised controlled trial (the highest quality study design to prove an idea) to unpick what we think we know about plant diversity and its impact on the gut microbiome.
To make it practical for patients/clients in clinic, I created a simple plant-point system: each plant type adds a point (herbs and spices earns a quarter point), encouraging variety across the super six. Eating the same plant twice a week – red bell peppers, for example – still only counts as one point unless you choose a different variety, for example, a yellow or orange bell pepper.
The benefits of plant diversity extend to oral health too. Studies have shown that enjoying more healthful plants (whole plant-based foods vs ultra-processed forms) show lower rates of gum disease and ulcers. Interestingly, the relationship may be bidirectional, whereby the oral microbiome may mediate the diet’s protective effect on the rest of the digestive tract.
Yet, while more diversity is generally better for the gut, oral microbiome health depends more on balance – the right mix of protective bacteria is key. Too little or too much diversity can tip things toward disease.
VS: Your work makes a strong case for joined-up thinking in healthcare. How do you see dental professionals fitting into the broader picture of preventive and personalised care?
MR: It is crucial that dentistry is viewed as part of whole-body medicine. Gone are the days of isolated specialism. We know that the oral bacteria don’t just stay in the mouth; they travel and can impact systemic disease. These findings highlight the importance and expanded scope of dentistry in overall patient care.
VS: Your keynote encourages clinicians to take a more holistic, future-facing view of patient care. For those just beginning to explore this way of thinking, what small mindset shifts or actions could make the biggest difference, both to their patients and to themselves?
MR: The mouth is the gateway to the body. What happens here doesn’t stay here. Oral health isn’t isolated, but one that influences digestion and overall health, and the implication of this is huge. For patients and clients, it’s becoming increasingly important to highlight and understand that good oral hygiene isn’t just about your smile – it’s part of whole-body health and wellbeing.
VS: Finally, what do you hope delegates will take away from your talk, and how would you like to see them apply it in their day-to-day practice?
MR: I want delegates to feel empowered to take a more holistic approach in consultations, with evidence-based tools and resources (from diet strategies to probiotics) to add to their ever-growing clinical toolbox. My hope is that they feel equipped with the latest science ensuring their practice stays at the forefront of microbiome research, recognising the central and bidirectional role of oral microbes in overall health.
The GBT Summit London 2025, hosted by EMS, takes place on Friday 31 October 2025 at the Royal College of Physicians, London. A highlight of the programme will be Dr Megan Rossi presenting her latest research on the oral-gut microbiome connection. Dr Victoria Sampson will also speak on the role of the oral microbiome in oral and systemic health.
Alongside them, a line-up of leading experts will share the latest science and strategies shaping preventive dentistry. This promises to be a landmark event for the profession and tickets are limited, so early booking is strongly recommended at ems-dental.com/gbt-summit-london-2025.
This article is sponsored by EMS.
