You’re Unique, So Your Nutrition Should Be Too: An Interview With Professor Tim Spector

Personalized nutrition uses the complex interaction between our individual characteristics and the food we eat to create tailored diet advice. Recent research has shown that modifiable factors, such as our microbiome diversity, have a much more significant effect on many of our responses to food than fixed factors, such as our age or genetics.

To learn more about predicting and modifying responses to food we spoke with Tim Spector, Professor of Genetic Epidemiology at King's College London, and author of The Diet Myth (2015) and the upcoming book Spoon-Fed (2020).

Molly Campbell (MC): How can genetic, metabolomic, and metagenomic information be utilized to predict an individual's metabolic response to food?

Tim Spector (TS): We know that everybody is different in terms of their genetics, the chemicals they have in their body, and the species of microbes they have in their guts. These three factors vary widely between people and affect their response to food.

In our PREDICT studies, we are gathering genetic, metabolomic and metagenomic information from thousands of people and monitoring their responses to food. We can then put all this data together using machine learning and come up with accurate algorithms to work out how someone will respond to foods that we haven't tested.

We believe that this ability to predict responses is the future of personalized nutrition. Our studies are still ongoing, but we are developing an app that should be available soon to educate people about their personal responses to food.

Karen Steward (KS): You authored the book “The Diet Myth,” what do you think are the most dangerous myths around diet and food?

TS: The number one myth is that there is "one true diet" that works for all. People think that if they follow a low-fat, calorie-controlled diet, they’ll lose weight and be healthy. Others believe that a high fat, low carbohydrate diet is the only way. But we've seen from our PREDICT studies that there are eight-fold differences in responses of normal people eating identical foods. Other studies have also shown wide variations in weight loss between people following the same diet, regardless of whether it’s a low fat or low carb plan.

The second myth is that food is very simple and can be categorized purely in terms of its macronutrient composition. People think that the only things that are important about a food are how many calories it contains and how much fat, carbohydrates, and protein it has. This focus on macronutrients and calorie counts has allowed food companies to sell us highly processed, poor-quality food because it ticks the "right" boxes. Our health has suffered as a result of eating this poor-quality food, not because of excess calories, fat or sugar.

The third myth is eating little and often – the idea that everybody should have around five or six small meals a day, and you should never skip a meal. The truth is some people have better food responses in the evening, so they should have most of their food then, rather than during the day. In our studies, we see that there's massive variation between individual nutritional responses, often involving factors which we didn't really think were important previously, like circadian rhythms. 

KS: In your food research with twins, what findings have surprised you the most? Have any of the results that have come out of your studies changed the way you think?

TS: We expected to find much greater similarities in the food responses of identical twins. For most conditions and traits, we find around 50 to 60% of the differences between people is due to their genes. But in the PREDICT study, we found that there was close to zero genetic effect for our response to fats and only about 30% for our response to carbohydrates. We were also surprised to discover that identical twins only share around 37% of the same gut microbes, only slightly greater than unrelated individuals.

MC: There has been a clear rise in the number of consumer genomics companies offering genetic tests relating to nutrition. What is your opinion on this?

TS: I think they're vastly overselling the ability to predict anything with genetic tests alone. Not only do our twin studies show that the genetic component , even if you had a perfect test, is fairly modest, but the actual tests they are doing only explain around one to two percent of the differences between people. So, although they are statistically significant in the population, once you get to an individual level, they're pretty useless and not much better than tossing a coin.

If people want to learn about their personal responses to food, and how they can eat to support their health, their best option right now would be to get involved with our PREDICT 2 study.

MC: The results of the PREDICT study suggest that genetics explains less than a third of metabolic responses to food, and most responses are potentially "modifiable." Please can you expand on this?

TS: Nobody's static. And the old idea that everybody keeps the same metabolicprofile for their whole life is clearly not accurate. So, the good news is that we can improve our responses to food. Simple ways to modify your responses include changing when you eat your food, whether you exercise before or after a meal, and changing how much sleep you get. 

You can also have a substantial effect on your responses to food by changing your diet. Increasing your fiber intake and eating lots of plants, fermented foods, and polyphenol-rich foods while avoiding highly processed foods and chemicals can increase microbiome diversity and therefore improve gut health and responses to food.

KS: There has been an explosion of interest in and research around the microbiome in recent years. What do you think are the most important messages in terms of food and the gut microbiome coming out of that research? From your own studies, what would you say are the key findings in this area?

TS: The main messages are that we all have a unique set of gut microbes, but our gut microbiome is modifiable. This means that everybody can improve that gut health by picking the right foods or altering their environment, such as having more outdoor lives or getting a dog. You can change your microbiome within a few days with a dramatic change; it doesn't take years.

But the effects of our microbiomes stretch much further than just our responses to food. We think that many health conditions related to modern living are a result of having a less diverse gut microbe population than healthy people. For example, our studies have shown that overweight twins lacked certain microbes that were abundant in their sibling twin.Recent research has also shown that there's a link between gut microbes and diseases like obesity, diabetes, mental health problems, and even Alzheimer’s disease.

The science of the microbiome is a young field that's developing rapidly, and we're finding out new things every day. But this is not a fad. The world of the microbiome is going to be here forever, and we're just scratching the surface of how powerful this science will be for our health.

Tim Spector, Professor of Genetic Epidemiology and Director of the TwinsUK Registry at Kings College London, and co-founder of the precision nutrition company ZOE, was speaking with Dr Karen Steward and Molly Campbell, Science Writers, Technology Networks.