“Even identical twins have different responses to food”: Landmark study highlights personalized nutrition potential

11 Jun 2019 --- Individual responses to the same foods are unique, even between identical twins, demonstrating that one-size-fits-all dietary guidelines are too simplistic. This is among the first results from the largest ongoing scientific nutrition study of its kind, led by an international team of scientists including researchers from King’s College London, Massachusetts General Hospital and nutritional science company ZOE. The findings highlight that a personalized approach to nutrition may provide better long-term health benefits.

This large-scale nutrition research project was born out of the Twins UK Study – a 25-year investigation of health and lifestyle in 14,000 twins led by Tim Spector, Scientific Founder of ZOE, Professor of Genetic Epidemiology at King’s College London and author of The Diet Myth. This study has produced over 700 publications, exploring the causes of a wide range of common diseases and health conditions.

After realizing that genetically identical twins had very different food preferences and responses, Spector teamed up with technologists Jonathan Wolf and George Hadjigeorgiou to create ZOE. A series of scientific studies in the US and Europe were set up involving thousands of volunteers in the field of nutrition and health. ZOE uses machine learning techniques to analyze the project’s nutritional data and is developing a consumer test and app, aiming to help people choose the right foods that optimize their personal metabolism, control weight and maintain good health.

For this part of the project, a total of 1,100 UK and US adults (60 percent twins) were studied for two weeks of regular blood sugar (glucose) monitoring of blood sugar, insulin, fat levels (triglycerides) and other blood markers in response to a combination of standardized and freely chosen meals. The results reveal a wide variation in blood responses to the same meals, whether they contained carbohydrates or fat.

Some participants had “rapid and prolonged” increases in blood sugar and insulin, which are linked to weight gain and diabetes. Others had fat levels that peaked and lingered in the bloodstream hours after a meal, raising the risk of developing heart disease.

This large variation is only partly explained by genetic factors (less than 50 percent for glucose, less than 30 percent for insulin and less than 20 percent for triglycerides) and there is only a weak correlation between an individual’s responses to fat and carbohydrates.

Identical twins who share all their genes and most of their environment often had different responses to identical foods. The study also finds that identical twins shared just 37 percent of their gut microbes – only slightly higher than the 35 percent shared between two unrelated individuals.

The proportions of nutrients such as fat, proteins and carbohydrates listed on food labels explain less than 40 percent of the differences between individuals’ nutritional responses to meals with similar amounts of calories. There are also large differences in responses to the same meals depending on the time of day they are eaten.

The results suggest that personal differences in metabolism, due to factors such as the gut microbiome, meal timing and exercise are just as important as the nutritional composition of foods. This supports the idea that simple nutritional labeling is insufficient for assessing food.

“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,” says Professor Spector.

The findings have been presented at both the American Society of Nutrition (ASN) and the American Diabetes Association (ADA) conferences. Dr. Andrew Chan, Professor of Medicine at Harvard Medical School and a gastroenterologist at Massachusetts General Hospital, comments: “It is reassuring that our genetic makeup only partially explains how our bodies respond to food. This underscores that our metabolism is not fixed – we have the power to change it. One exciting avenue is to tailor our diets to the bacteria in our gut that helps us metabolize nutrients.”

“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,” added Dr. Sarah Berry, Associate Professor in Nutritional Sciences at King’s College London and Scientific Advisor at Zoe.

The next phase in the research project will be to recruit more than a thousand volunteers across the US who want to understand their own personal responses to food and contribute to nutritional science by taking part at home. 

The breadth of these findings are significant, as experts in the field have noted that the personalized nutrition space can lack solid, scientific underpinning, especially when it comes to the microbiome. However, aside from scientific backing, the personalized nutrition space must also pay attention to the psychological and social aspects of behavioral change. In this way, the advice must be compelling enough so that people are empowered to change their behavior around food and nutrition. Essentially, you need to know the consumer from a biological standpoint, but also from a psychological perspective for competent personalized advice, according to Nard Clabbers, Senior Business Developer Personalized Nutrition at TNO.