By Kathleen Doheny
WebMD Health News
Reviewed by Hansa D. Bhargava, MD
Nov. 19, 2015 -- Experts have long known that a diet that works for one person doesn't help another person shed a pound. Now a new study finds that even if we all ate the same meal, we'd burn it differently and have different blood sugar levels afterward.
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Researchers say the findings will help pave the way for personalized nutrition. One day, we may have diets based on how we respond to foods so that we can keep our blood sugar at healthier levels. High levels are linked with a number of health problems, including obesity, diabetes, heart disease, cancer, and strokes.
"Each human being has a unique response to the food he or she consumes," says Eran Elinav, MD, PhD, a researcher at the Weizmann Institute of Science who worked on the study. "We need to look at individual responses."
Their research, he says, ''shifts our view from this one-size-fits-all dietary approach to a personalized dietary approach and regimen."
The researchers used a smartphone app to collect data. Someday soon, our smartphones may be armed with information about our unique pattern of breaking down food. And we could simply ask our phones: "What should I eat now?"
Why Personalized Nutrition?
People's blood sugar levels are rising, and that's reflected in the sharp increase in prediabetes (which means you're on the path to diabetes), the researchers say. But there's no accurate method for predicting how blood sugar will change after a meal.
One method that tries to estimate that is called the glycemic index, which ranks foods based on how they affect blood sugar levels. But it assigns a score to a single food, so it's not practical for real-life meals with an assortment of foods, the researchers say.
The difference in how people respond to what they eat may be explained in part by how we use the simple sugars left after we digest it. We absorb these simple sugars mostly in the small intestine, and the researchers found that specific microbes there are linked to how much blood sugar rises after a meal.
The researchers used a glucose monitor to track the blood sugar levels of 800 people continuously over a week as they ate nearly 47,000 meals. The men and women were of various weights. Some had prediabetes.
People used a smartphone app to log when they slept, exercised, and ate. They also provided stool samples so their gut microbiome -- the bacteria in your gut -- could be analyzed.
"The first very big surprise and striking finding was to see the very vast variability we saw in people's responses to even identical meals," says researcher Eran Segal, PhD, a computational biologist at the Weizmann Institute of Science. Some people who ate bread had no blood sugar changes, while others had high blood sugar. One obese woman with prediabetes had a blood sugar spike when she ate what most would consider a healthy food, a tomato, Segal says.
The researchers then used this information to predict how each person's blood sugar would react after specific meals. They eventually developed personalized diets for 26 people. Next, they needed to see if personalizing the diet improved blood sugar levels.
The diets reduced their blood sugar levels after meals and altered their gut bacteria.
For instance, one participant in the last study received two menus. One included muesli for breakfast, sushi for lunch, corn on the cob and nuts for dinner, and a marzipan snack, Segal says. The second menu included eggs and bread with coffee for breakfast, hummus and pita for lunch, vegetables and tofu for dinner, and an ice-cream snack.
Both days' menus included roughly the same number of calories, but the first menu raised the person's blood sugar levels much more than the second, Segal says.
Personalized Nutrition: Perspective
The report will be potentially useful to people, since blood sugar is linked with health ailments, says Peter Turnbaugh, PhD, assistant professor of microbiology and immunology at the University of California, San Francisco.
The study was funded solely by academic funds, the researchers say. Now they are in licensing discussions, hopeful that the program will be commercially available soon.
Experts know that people's blood sugar responses vary a lot, Turnbaugh says, but what was missing was ''a way to use that information in a way that would be useful."
SOURCES: Zeevi, D. Cell, published online Nov. 19, 2015. Press conference, Nov. 16, 2015. Peter Turnbaugh, PhD, assistant professor of microbiology and immunology, University of California San Francisco.
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