Were you ever frustrated when a diet plan that helped a friend lose weight didn’t work for you? Scientists working in the emerging field of personalised nutrition believe they can now explain why. Simply put, the answer is we process the foods we eat differently.
"Some people are maybe trying to lose weight and the diet that they are following isn't actually tailored to their metabolism," says Prof Lorraine Brennan of University College Dublin's (UCD) School of Agriculture and Food Science. "They would have a better chance of losing and keeping their weight down on a diet that is more tailored to them."
The idea that obese people may carry extra weight because of their metabolism is not one that has tended to attract sympathy. However, when it comes to how we all process food, the evidence is clear; we are all very different and have individual dietary needs.
We are familiar with the food pyramid which puts vegetables and fruit at the bottom and foods high in fat, sugar or salt at the top. The nutritional advice, generally speaking, is to eat more of the good stuff at the bottom of the pyramid and less of the bad at the top.
The problem with this catch-all advice when it comes to our nutrition is that people are different. Over the past 10 years or so scientists working in the field of what’s now called personalised nutrition have found everyone responds to food in different ways.
The evidence initially came from monitoring people’s blood glucose levels. The scientists placed little patches on people’s arms capable of monitoring glucose levels every 15 minutes. They found that people were eating the same food but often having hugely different responses in their blood glucose levels afterwards.
In nutrition studies some participants see their blood glucose levels staying flat even after eating an ice cream, while others see their levels jump up, says Brennan.
Her research team examined how people processed breakfasts either high or low in protein. They saw huge variation in how people were responding to the food in terms of their blood sugar levels. This tied in with what was being found in other nutrition studies.
The evidence suggested an individual approach to nutrition and that nutrition guidelines were required. It also led to a new research field called personalised nutrition where scientists began to distinguish the many ways we are different when it comes to processing food.
Scientists working in personalised nutrition say they are not out to consign general nutritional guidelines from governments to the bin but to keep these in place while identifying what a person’s dietary needs might be and to tailor an individual dietary plan accordingly.
If a person is older they might be advised to get enough protein, says Brennan. Or someone else who spends a lot of time indoors might be advised to get outside more to get more vitamin D.
Scientists want to find out precisely why people respond differently to foods. Once they have answers to that question the next step is to be able to provide personal dietary advice for people based on their blood sample. A person of a certain age, gender and race who has an illness such as cardiovascular disease could be presented with a personal dietary plan to suit their exact needs.
The question of who will respond to a dietary intervention, who won't and why is key for researchers. Prof Baukje de Roos, a nutritionist at the Rowett Institute at the University of Aberdeen, is aiming to better predict dietary "responders" and "non-responders".
The benefit of dietary changes for responders, says de Roos, can be akin to a drug. “We did a study where we gave wholegrain products to people to lower their blood pressure. We found a group where the lowering of the blood pressure was as powerful as any ace inhibitor, the most common drug prescribed for lowering blood pressure.”
“We are using statistical ways to see, first of all, who are responders and who are non-responders,” de Roos says. “Measuring people once may not be enough to identify a person as a responder but if people are measured several times and consistently have the same response then I can identify you as a responder.”
The collection of micro-organisms in a person’s gut is called the microbiome. It is different in each person and it is an important influence on their health status. Scientists are working on ways to measure the microbiome and make changes to it where required.
The latest scientific evidence suggests that making changes to a person’s microbiome might not be an easy task. “It can be hard to shift it,” says Brennan. “So you might shift it for a couple of weeks if you have a drastic dietary change but then, [according to] the most recent study I’ve seen, it goes back to its original state again.”
There are many reasons why a person develops a certain microbiome such as diet, antibiotic usage, exercise levels and where they live or grew up, she says. The goal is to find ways to make the lasting changes to the microbiome needed to maintain a person’s health.
Genetics is part of the puzzle when it comes to unravelling why some people are more prone to diseases like diabetes and obesity, says Brennan, but no more than that. “We all thought now we’d be able to find the gene for diabetes, for every disease, but we just haven’t found that. It shows the complexity of it all.”
There have been some recent dietary studies which showed that, for some people, making a change to their diet was as effective, or even more effective, than taking a drug. This begs the question as to whether better personal dietary advice will make drugs redundant?
Brennan doesn’t think so. “If someone is ill they have to take medicine and look for the correct advice and be seen by a medical practitioner,” she says. “Where diet can come into play is the prevention aspects and trying to get people at an early age and long before there is any illness or metabolic disorder.”
She imagines a scenario where a person attends their GP, gets a blood test and based on that they are referred to a dietician who advises them to perhaps increase their fibre, lower their carbohydrates or increase certain types of fat in their diets.
For personalised nutrition to work it requires scientists to become very good at identifying biomarkers of disease in people’s blood. The better the biomarkers the better scientists can predict how much a person is at risk of developing a disease such as type 2 diabetes and this is a big area of research for Brennan and her colleagues at UCD.
"We are looking at people who have developed cardiovascular disease but we have samples too from when they were healthy," says Brennan. "We are going to do a large intervention study with Prof Jayne Woodside in Queen's University Belfast to see how to deliver personalised nutrition in about 100 individuals."
Precision nutrition goes further by pinpointing a person's dietary needs. Prof Lydia Afman, a human nutrition and health scientist at Wageningen University and Research in the Netherlands, is working on what she calls a personalised digital twin. This is an algorithm which makes dietary predictions for an individual using the latest machine-learning and artificial-intelligence scientific techniques.
Afman’s focus is on trying to understand what food people need to suit their precise situation. “You can have two people with the same BMI, the same gender, same age and they can still need a different type of food,” she says.
In 10 to 15 years’ time, Afman predicts, personalised digital twins will be integrated into our health systems. “It is going quite fast, we will have our demo model ready in three years.”
The field of personalised nutrition will provide each of us with perfectly tailored diet plans that work – just for us.