Researchers have found that many widely accepted dietary guidelines are not suitable for everyone, with even twins responding differently to the same foods, despite having nearly identical DNA. This discovery complicates health advice and emphasizes the need for individualized dieting plans.
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The new study is the largest scientific nutrition study of its kind and was carried out by researchers from King’s College London, Massachusetts General Hospital, and ZOE, a nutritional science company that is developing personalized nutrition tests.
The study, called PREDICT, included approximately 1,100 adult volunteers from the US and UK, including 240 pairs of twins. For two weeks, every participant was asked to eat certain meals and keep track of every single item of food and drink they consumed.
From this, researchers were able to analyze how blood levels of sugar, insulin, and fat changes responded to specific meals over the two-week study duration. Researchers also gathered data on activity, sleep, hunger levels, and gut bacteria.
Professor Tim Spector, a Professor of Genetic Epidemiology at King’s College London and the lead researcher spoke on the importance of the new study:
The sheer scale and detail of our scientific project is such that for the first time we can explore tremendously rich nutrition data at the level of an individual. Our results surprisingly show that we are all different in our response to such a basic input as food. It was a real shock to see that even identical twins have such different responses.”
Adding to Professor Spector’s comments, co-founder and CEO of ZOE Jonathan Wolf said, “For most of us, the food we eat is the most important medicine we take. And yet we are all profoundly confused about what is good for us. We believe that combining science and machine learning can solve this, by understanding for the first time our individual responses to food.”
DNA is not as important as once thought
Results of the study were presented at the Nutrition 2019 conference and found that individuals had markedly different responses to the same meals, even if their DNA was almost identical, as is seen in twins.
Identical twins that were found to have different responses to the same foods only shared 37 percent of their gut bacteria, which is only two percent higher than the 35 percent unrelated individuals share. This small overlap in twin’s gut bacteria may explain why their nutritional responses were so different, despite their very close DNA match.
The study’s findings also suggest that individual differences in metabolism because of an individual’s gut bacteria, as well as timings of meals, and exercise, are as important in healthy diets as the nutritional makeup of the food consumed, and DNA may not be as important in determining nutritional responses as is widely believed.
Discovering these differences led Professor Spector to hypothesize that diets could be tailored around the microbiome and not just the genome, which could bring on an era of personalized eating and dieting. However, the microbiome is still not fully understood despite it being implicated in many bodily functions.
The results have the potential to complicate health and weight loss advice with the implications that nutritional needs are highly individual from person to person.
“Our recommendations, medically and public-health wise, have just been assuming that if people follow the standard plan, they’ll lose weight,” said Spector.
With his study, he says that line of thinking has “now been exposed as completely flawed.” However, he also added that this doesn’t debunk all nutrition advice:
“It doesn’t mean you throw [all nutrition advice] out,” he said. “There are some guidelines and recommendations around the world that near-everybody agrees on.” These guidelines include following a diet that is rich in fiber and low on processed and calorific foods.
Dr. Sarah Berry, a Senior Lecturer in Nutritional Sciences at King’s College London and Scientific Advisor at ZOE said:
For the first time, we’re expanding large-scale nutritional research beyond blood sugar. These findings show that the responses to food of a number of key metabolic markers – including triglycerides, insulin and blood sugar – are highly individualized. No one has been able to combine data on this scale before.”
‘We’re not there yet’
Although these findings could open the door for gene-specific dieting, with individuals being able to access data on their specific genetic makeup and the corresponding diet that could help them to lose weight and keep healthy, Deborah Good, an associate professor of human nutrition, foods, and exercise at Virginia Tech, warned:
“We don’t know enough about all the different things that contribute to it. Sometime in our lifetime, we may be able to, at least genetically, be given a set of information at the beginning of our lives [about our health needs]. But we’re not there yet, and I don’t know how long it would take.”
PREDICT will continue into PREDICT 2, which is an expanded home-based study that began in June 2019. This study will include 1,200 volunteers across the US and UK whose nutritional responses to food will be measured over a period of 11 days, including data on their moods, sleep, and physical activity.
ZOE co-founder and President George Hadjigeorgiou said that everyone “deserves to understand how they respond to food so that they can make confident decisions about what to eat and be in control of living a healthier and more enjoyable life,” and as such, the long-term goal is to make ZOE’s studies into an at-home kit and an app that the general public can download to access dietary recommendations.
The goal of ZOE and looking at this data is taking a holistic approach to your health. Someone might use it for [weight management] while someone else might want to raise their metabolism or reduce their chances of getting diabetes. It can be used for many different purposes.”
Professor Tim Spector, Lead Reseacher
The ZOE app should be available by 2020. Find out more on the ZOE website.