A recent podcast episode on the Medicine Made For You series takes a deep dive into the future of healthcare.

It’s time for a deep dive looking at the food we eat and how dietary advice could soon get a lot more personalized.

We start with muffins. Our producer Gemma Ware tells the story of a two-week nutritional study run by King’s College London that she took part in with her identical twin sister, aimed at trying to better understand which factors influence how we react to particular foods.

A core part of the study, called PREDICT, involves eating muffins, prepared by the research team with different levels of fat, sugar and fiber, and doing multiple blood tests afterwards to measure the reaction.

Tim Spector, professor of genetic epidemiology at King’s College London, and who is leading the study, explains:

Up to recently, say, the last ten years, we’ve been thinking that the difference between people and how they respond to food is primarily down to their genes. And this has led some people to have a rather fatalistic view of dieting and health and everything else and say, “well, I’d blame my parents”.

Spector explains that through the researchers’ ongoing analysis of more than 2 million data points from the PREDICT study – which includes data from sets of identical twins who share 100% of the same DNA – scientists are now able to separate how many of the differences between people’s bodily responses to certain foods are down to their genes. And everybody reacts differently, even identical twins.

When it comes to a person’s reaction to sugar, for example, the researchers foundthat about 30% could be explained by genes, but for a person’s reaction to fat it was only around 5%.

The more we find out about the human body the more complex it is. And it’s definitely not all explained by genes and it’s definitely not all explained by microbes. And we’re finding other things we didn’t think were important do have a role.

Now the results are available to participants in a new app, which gives personalised recommendations on how healthy certain foods or meals are for your body, based on the study results. We put it to the test.

Part of the analysis is based on the diversity of a person’s gut microbiome, and the influence this has on metabolising the food they eat. To find out more about the importance of these gut microbes we visited the (pretty smelly) lab of Glenn Gibson, professor of food microbiology at the University of Reading, to see the models of the gut his team have created.

Gibson says he’s not convinced that we’ll ever get to a point where it’s possible to personalise dietary advice based on a person’s individual microbiome:

Because it would suggest that every single person has a rather different diet to propel their gut microbiota in terms of their own health. And I don’t think that is necessary. We kind of know which microbes in the gut are positive for health and which ones are negative. And so I don’t think that individually, there are going to be massive differences in those bugs.

Gibson explains that he thinks the factors that influence the health of the gut microbiome are more environmental than genetic.

When it comes to genes, there’s still a lot researchers don’t know for certain about the way our genes and diets interact, and this means that personalising dietary advice based on someone’s DNA is so far, quite limited.

But even if people do have more personalized dietary advice available at their fingertips in the future, will they use it? Julie Lovegrove, Hugh Sinclair chair in human nutrition at the University of Reading, explains the results of a study, called Food4Me, that looked at how people responded to different types of personalized advice. Some people in the study received advice based simply on their diet, some based on their phenotype risk, such as whether they have risk of high cholestoral or diabetes, and some based on their genes.

While Lovegrove says that the overall personalization did have a beneficial effect – on how much red meat or saturated fats people ate – the type of personalization didn’t have much impact.

I think we have to understand with our colleagues in psychology, for example, what motivates people to change. And I think we are all motivated by different things. And I think we also must frame it in a way that people can not only take on board, but understand the importance of that.