Dr Daniela Weiler: “We are what we eat.”

Why are the bacteria populating our mouth important for our entire body? And how can proper nutrition lead to improved overall health and even have a preventive effect against cancer?

Dr Daniela Weiler, who works in the oncology department of the tumour centre at Lucerne Hospital and is also a specialist for nutritional medicine, explains the connection between oral and overall health.

Is oral health the gateway to overall health?

That is certainly true. But it is not just bacteria that find their way into our bodies through the mouth. I see it in an even larger context.

The mouth is the gateway through which all the nourishment we consume passes. What we eat and what we drink is of paramount importance to our health. And the gateway-to-health analogy is correct because the mouth cannot be viewed in isolation from the rest of the body. 

The correlation is particularly evident when we are talking about inflammation. Inflammation in the mouth can affect the whole body. A state of chronic inflammation originating in the mouth has a considerable impact on the entire body.

Can you describe the effect such an inflammation can have?

Let’s take periodontitis (gum disease). The bacteria in question populate the mouth, but we can also detect them in tumours. We suspect that these bacteria – we are talking about Fusobacterium nucleatum, Porphyromonas gingivalis and Treponema denticola – migrate from the mouth into the intestines, for instance. They can be detected in colon cancer. They have also been found in ear, nose and throat tumours. As well as in pancreatic cancer. Conversely, it is evident that tumour patients with these diseases also show a higher incidence of gum disease.

Is anyone currently involved in research interested in these links?

A new study that deals with this very topic has just been published. Data is available. A convention in Rome recently reported on bacteria that are present on the biofilms on colon tumours – but can also be found orally. The research is still in its infancy.

However, the microbiome research is gradually finding its way into a clinical setting. We are discovering more and more connections and are aware of the importance of microbiomes in the treatment of cancer. A lot will happen in this respect in the coming years. 

What is a microbiome? 

A microbiome is the entire diversity of micro-organisms that we carry on and in our bodies. Our guts are host to around 100 trillion bacteria. Our bodies consist of 10 percent human and 90 percent non-human cells; the latter include viruses, fungi and bacteria. That’s an impressive ratio. Most of our bacterial flora can be found in the gastrointestinal tract; some are found on the skin. We know from research that there are around 15 billion bacteria between each tooth. The figures are incredible. 

It is important to realise, however, that not all of these bacteria are harmful. Some are essential. Research assumes that 80 percent are ‘good’ bacteria. The pivotal question, of course, is how to remove the harmful bacteria without destroying the good bacteria.

Is that possible?

I think it is possible with the right nutrition, which is where I come in with my speciality. Our choice of food can have a powerful impact on our intestinal bacteria and their diversity. It has been proven that, over the centuries, humans have unfortunately lost a lot of this diversity. 

Why do you put such emphasis on bacterial diversity?

Two major studies have shown a direct link between bacterial diversity and overall health. What kind of diet is conducive to promoting bacterial diversity? In short: eat more fibre. Consume less sugar and fewer trans fats, less white flour and meat. Eat more plants with their fibres! 

How long does one have to change one’s nutrition before the microbiome reacts?

It only takes a short while. Studies report changes in the microbiome within just one week. It is important to change one’s nutrition permanently, not just for a limited time. This isn’t a short-term fix. 

Are there different types of people who require different nutrition?

I don’t think so, but that’s my opinion. I’ve never come across scientific proof that backs this up. Providing clinical evidence – as is required for medications, for instance – is practically impossible. But it is possible to describe very clearly what is healthy, even if the food industry holds other opinions and interests. 

In your brochure on nutrition, you describe a three-pillar concept. What does that mean?

This is my own definition of the three most important aspects in cancer prevention – nutrition, exercise and stress management. Alongside treatment, they can contribute to a better prognosis when dealing with cancer. This is scientifically supported and proven. 

The three-pillar approach can also be applied to primary cancer prevention. Many observational and interventional studies deal with primary prevention – all too often, however, they only examine limited nutritional strands, such as nut or olive oil consumption. 

To sum up: proper nutrition through the mouth leads to better prevention and also a higher likelihood of surviving cancer?

There is scientific support for this conclusion. The area where we have the least data is in palliative medicine, i.e. where we are already dealing with metastatic cancers.

And we can even go a step further: a plant-based, wholemeal diet also has a positive impact against dementia, cardiovascular disease, diabetes and rheumatic diseases. And although the benefits may not be 100 percent proven in all these cases – this form of nutrition is not harmful. It certainly has fewer side effects than any of the medications used to combat the diseases.

Let’s look to the future: could a regime that combines oral hygiene with nutrition improve cancer prevention?

It could certainly improve primary prevention. What we put in our mouths is of paramount importance. Another exciting facet is the interplay between the microbiome and in particular between the intestinal bacteria and the brain. Our brains and intestines communicate with one another.

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