There is no such thing as a healthy diet that will work for everyone. People respond to food in such idiosyncratic ways that everybody needs a personalised eating plan, according to results from a study that looked at the effects of genetics, the microbiome and lifestyle factors on metabolism.
The study fed 1102 healthy people identical meals for two weeks and measured their metabolic responses. These varied wildly, with up to tenfold differences, meaning that a healthy diet for one person could be unhealthy for another. “Everyone reacts differently to identical foods,” says Tim Spector at King’s College London.
He and his colleagues measured levels of glucose, insulin and triglyceride fats in the volunteers’ blood. High levels of all three after eating are a risk factor for obesity, while people who show glucose and triglyceride spikes after eating are more likely to develop cardiovascular disease and diabetes.
The team also tracked the volunteers’ sleep, exercise and hunger levels, and took stool samples to assay their gut microbes. Spector, a geneticist, says he expected to find a strong genetic component to the metabolic responses, but actually saw very little. The volunteers included several pairs of identical twins and even they showed very different responses to the same meal.
“That told us straight away that genes don’t play a major part,” says Spector. “How we respond to a fatty meal has virtually no genetic component at all, for example.” His team found that only about 30 per cent of glucose response is genetic.
Other factors such as gut microbes, circadian rhythms and sleep and exercise are more important, says Spector. The timing of meals also matters. Some people metabolise food better in the morning while others saw no difference in their ability to metabolise food throughout the day.
This suggests that it would be more effective to design a tailored heathy-eating programme for individuals rather than recommending a one-size-fits-all diet.
The results can be surprising, says Spector. He says he ate tuna and sweetcorn sandwiches for years thinking they were good for him, but recently found out that his metabolism responds very badly to them.
Spector and his team have also developed an AI tool to predict people’s responses to food, based on their genes, gut microbes, exercise and sleep patterns and metabolic responses to food. A UK-based company called Zoe has turned this into a consumer test and smartphone app that will be rolled out in the US next month and the UK later this year.
“It’s a very exciting study,” says Bernadette Moore at the University of Leeds, UK. “The really significant factor for me is that they did it in twins, so they had a really powerful design to examine the genetics.” However, there is still more work to be done to fully understand individual responses to food, she says.
“The study findings are impressive,” says Yiannis Mavrommatis at St Mary’s University, London. “Its initial findings will shape the future of nutrition science.”
Journal reference: Nature Medicine, DOI: 10.1038/s41591-020-0934-0
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