Microbiome Manipulators: A New Role for Dietitians
There’s no doubt: the gut microbiome is the hottest topic in gastroenterology – and overall health – today. Now, as an increasing body of research reveals the links between gut health, diet and disease, dietitians are set to become “microbiome manipulators”.
We asked two leading experts – world-leading neurogastroenterologist Nicholas Talley, Pro Vice-Chancellor (Global Research) & Laureate Professor at the University of Newcastle, and Professor Mike Gidley, Director of the Centre for Nutrition and Food Sciences (CNAFS) at the University of Queensland – our burning questions.
Why is a healthy microbiome important?
Says Prof Talley, “There’s a huge number of bacteria and other living organisms that are in the gut –and also just about everywhere in the body. We are now realising that these organisms are regulating our health, keeping us healthy – and are significantly relevant to numerous diseases.”
“We now know, very clearly, that the bacteria that live with us, in us and around us are absolutely essential to our survival. No bugs, and we’re not here.”
What does a healthy microbiome look like?
“There are three factors that most people agree on,” notes Prof Gidley. “First, the microbiome should be diverse, with many different types of bacteria – essentially, the more, the better. Diversity is critical. Second, that diversity should predominantly be microbes feeding off of carbohydrates, and not feeding off proteins.
“The third is lack of pathogenic microbes, essentially gut infections which are reflective of poor gut health. If you have a poor microbiome, you are more at risk of having gut infections. A diverse, carbohydrate-fermenting microflora is protective against pathogenic incursions.”
What do we know about the link between the gut microbiome and disease?
“Whenever you look for a correlation between features of the gut microflora and almost any aspects of human health, there tends to be some association.” says Prof Gidley. “So, the effect of the microbes in our gut is not limited to our gut, and the consequence of having a healthy bacterial population in our gut impacts on many of the processes that result in a healthy or non-healthy state.”
“We know that the microbes talk to the gut mucosa, to the nerves in the gut, and they communicate basically with the rest of the body through this mechanism.
“A significant number of gut diseases – from inflammatory bowel disease to irritable bowel syndrome to functional dyspepsia – and probably even a number of conditions like anxiety and depression – are likely linked to the bugs, the composition of the bugs, and how they talk to each other and the rest of the body”, Prof Talley.
How can we help create a healthy microbiome?
Prof Gidley explains, “Diverse food leads to a diverse microbiome – that’s the current hypothesis. The next logical step is to connect that back to the dietary guideline advice, which is to eat a variety of foods that includes vegetables, fruits, wholegrains and other plant foods, legumes and so on.”
“Think of the large intestine as a fermentation vessel. There are bacteria there, and they have to have something to ferment. As long as you’ve got a good diet, then your bacteria will be feeding off your dietary fibre – vegetable, wholegrain and fruit fibre – because this is not digested in the small intestine.
“However, fibres have a variety of different effects – fibre ain’t fibre. Certain types of fibres are fermented rapidly, such as the soluble small sugars that are dissolved and quickly fermented; then, at the other extreme, you have woody, cellulosic tissues that are hardly fermented at all, such as sweetcorn kernels.
“A good healthy diet has components that have different rates of fermentation that ensure we have a 24-hour process of fermentation. You want to feed the gut bacteria in a slow, steady, drip-feed with a variety of types of fibre – from a variety of types of food.”
What are the consequences of a diet without adequate fibre?
Prof Gidley points out that the microbiome helps explain some of the dietary advice we’ve been giving our patients. “We’re now starting to understand what’s behind the dietary recommendations to include a diet rich in fruit, veg and whole grains – your microbiome has a lot to say in that respect.”
“If you don’t have enough fibre getting to the large intestine, then you have primarily other food components and digestive secretions that are protein-rich, and in the absence of fibre the bacteria have to ferment protein. The same thing happens if we have too much protein compared with fibre in our diet.
“Fermenting protein without fermenting carbohydrate is commonly considered a bad thing. If you ferment protein directly, then some of the end products are toxic – which may explain the risk of colon cancer. If you have fibre being fermented at the same time, that’s not a problem, because those toxic products can be mopped up by the bacteria that grow.”
The best fibre, according to Prof Gidley, comes from whole foods, so there is no need to look for foods with added fibre: “A diverse microbiome comes from diverse kinds of fibre, and the way to get that is diverse foods.”
How long does it take from changing the diet to seeing a change in our gut health?
“Imagine microbes with lives of hours to days; the population can change quickly, probably in one to three weeks,” says Prof Gidley. “The good news is, the dietary changes we make can have an effect over a manageable timeframe.”
Can dietitians really make a difference to the microbiome?
“If you alter your diet – and as a dietitian that’s what you teach people to do – you do change the microbiome,” explains Prof Talley. “Dietitians need to be experts in what different eating patterns do to the microbiome. I suspect new microbiome knowledge will change the practice and some recommendations of dietitians.”
“The best example I can think of is the low FODMAP diet for IBS, where we know it works in about 50–70% of IBS cases. When we give the microbiome a high fibre diet – or a low or high FODMAP diet – we change it. Any significant diet will change it, so dietitians are microbiome manipulators.”