Dr Juliet Ansell is the lead researcher in Plant & Food Research’s human gut health programme. The research aims to better understand the interactions that go on between food, gut bacteria and health.
Recent findings indicate that foods can have an impact on the immune system through interaction with gut bacteria.
Juliet’s research is focused on 3 main areas:
- Gathering information about what is happening to different plant foods as they pass from mouth to stomach to colon in an artificial lab-based setting (in vitro).
- Using animal models (in vivo) to verify the information gathered in the in vitro experiments.
- Applying the knowledge gained in the in vitro and in vivo experiments to run human trials.
One of the difficulties encountered with the in vitro work is trying to mimic the anaerobic conditions that exist in the large intestine. It is essential to create an oxygen-free environment, and several ways of achieving this have been developed. For example, a shoe-box size anaerobic chamber has been developed that allows small-scale experiments to be run cheaply and rapidly.
Animal models allow the results of the in vitro work to be tested in a living animal system. If the results of these trials look promising, a human clinical trial may be set up. Such trials are very expensive to run so the results from the in vivo work need to be conclusive before taking this step.
Results to date
Evidence has been gathered showing that the bacterial populations in the small intestine and large intestine are responsive to the presence of non-digested parts of plant foods such as cellulose.
Foods such as broccoli, kiwifruit, apples and berry fruit have been tested, and it has been found that, when eaten as part of a normal diet, these plants result in an increase in the number of bacteria belonging to the Bifidobacterium genus present in the gut. These bacteria are known to inhibit the growth of pathogenic bacteria, and so an increase in their numbers is thought to provide added protection.
In addition, there is evidence that shows beneficial changes to the metabolism of the bacteria with increased amounts of short-chain fatty acids such as butyrate and propionate being produced. These acids not only act as an energy source to the cells lining the gut but also have a positive impact on the overall health of the gut and its resident bacterial population.
Juliet’s team is now focused on how the bacteria and their metabolic products interact with the lining of the gut. The lining has a rich array of cell types, and it is the immune cells that are of particular interest. One of the aims is to discover how the immune cells promote a tolerant response and natural protection from opportunistic pathogens.
Nature of science
Scientists often use models to investigate aspects of science because it is sometimes too difficult to trial the real thing. Juliet’s research team is using animal models instead of human volunteers to verify information gathered in the laboratory.
It has been estimated that there are more bacteria in the large intestine than there are cells in the body. Maintaining a healthy bacterial population in the large intestine plays a key role our sense of wellbeing. Use our article Healthy gut bacteria to explore this further.
Watch this animated video on how food is processed as it moves through the digestive system.
In this fermentation activity students set up an alcoholic fermentation, prepare and view a slide of bacteria responsible for monolactate fermentation and find out about gut bacteria fermentation.