By Dr Jia Li, Senior Lecturer and Grace Barker, PhD student, Imperial College London
There are about 100 billion stars in the Milky Way Galaxy. It’s massive, isn’t it?
But the microbial ‘universe’ hidden in your body is even bigger. There are an estimated 38 trillion bacterial cells on, or in you. If you scoop out 1 gram of your faeces, the number of bacterial cells is similar to the number of stars in the Milky Way. These tiny bacteria, together with other microorganisms like archaea, fungi and viruses, are called microbiota. These microbiota help us to train our immune system and digest food that we ordinarily wouldn’t be able to. They ‘talk’ to each other and to us using a chemical language, and they play a key role in our health and disease.
Getting comfortable with bowel talk
Our research team works on metabolic interactions (‘chemical language’) between the gut microbiota and the diet, and the impact of these interactions on our disease risk, particularly bowel cancer (colorectal cancer, CRC). CRC is the third most commonly diagnosed cancer and the fourth leading cause of cancer death worldwide. Additionally, the alarming finding that rates are rising among young adults, in whom CRC was previously rare, made headlines recently.
Despite the huge and far-reaching impact of CRC, it can be a difficult disease to discuss; although poo is a crucial indicator of our health, bowel habits don’t tend to make great dinner party chat. However, at Imperial College London’s Division of Systems and Digestive Medicine, we really don’t have many reservations when it comes to discussing gut health.
Our research aims to find out more about how we can help prevent CRC by investigating the link between diet, the microbiome and the colon. And in making this our number 1 aim, we’ve had to investigate what’s going on with a lot of number 2s. More on that later…
Global differences in CRC
Curiously, rates of CRC significantly vary around the world. The highest of which are reported in highly developed countries such as the USA and the UK, and the lowest in rural communities, such as those in rural Africa. Could investigating what is driving this geographical disparity help us to learn more about how we can prevent CRC?
Research suggests that the reason for this global variation is not predominantly genetic. This led us to consider environmental factors such as dietary habits. It’s long been thought that an unhealthy diet, particularly one low in fibre, could be a major contributing factor in CRC development. That’s why we’re investigating how different components from diets eaten by high- and low-CRC risk populations around the world could help promote or prevent CRC.
Learning more through diet-swapping
Our research began by swapping the diets of African-American volunteers — a high-CRC risk group and consumers of a typical ‘Western’ diet — and rural African volunteers, who exhibit low CRC risk and consume high-fibre, mainly plant-based foods. After two weeks of dietary exchange, we took faecal samples, as well as small samples from the surface of the colon. The results were staggering.
With only 2 weeks of eating an ‘Africanised’ high-fibre, low-fat diet, African-American volunteers showed reduced signs of inflammation and cell growth, suggesting a reduced risk of CRC. Analysing faecal samples using metabolic profiling, a method to measure chemicals in our body fluids, also revealed huge changes in certain bacterial products, most notably those known as short-chain fatty acids and bile acids.
Adapting our diets for the future
More detailed analyses of these microbially-derived products and what they mean for colonic health are currently underway in our laboratory. The results also prompted a second trial, which is now taking place in Alaska.
Alaskan Natives have the highest global incidence rate of colorectal cancer and eat a diet unusually high in meat and fat and low in fibre, making them a very interesting population to study the impact of diet on CRC risk. Our Alaskan volunteers have agreed to take a fibre supplement, alongside their regular diet, for 2 weeks. From this study, we’re hoping to see if fibre supplementation can protect against CRC, especially in high-risk populations.
We hope that the results of these trials can help us to understand precisely how diet is linked to CRC risk, 1 faecal sample at a time. We’re optimistic our work could help influence dietary guidelines in the future, particularly those advising on fibre consumption, and ultimately help reduce preventable cases of CRC around the world.
Dr Jia Li is a Senior Lecturer for the MRes in Microbiome in Health and Disease based at the IGHI’s Centre for Digestive and Gut Health.
Grace Barker obtained the MRes in Microbiome in Health and Disease in 2017 and was awarded the Dean’s Masters Prize at Imperial College London, and has continued with her PhD in this area.