Which foods are healthy?
It's a question nearly every adult - and probably most children - would feel comfortable answering, at least in part. After all, who's going debate the merits of broccoli or tomatoes?
But discerning which foods are healthy and which aren't is complicated. Everybody metabolizes food differently, so what's healthy for one person might actually be unhealthy for another, suggests convention-upending new research.
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Take the tomato.
A woman with prediabetes who participated in the study ate tomatoes several times a week. Tomatoes are considered low glycemic, or a food that won't significantly raise blood sugar. When she ate tomatoes, however, her blood sugar soared.
"For this person, an individualized tailored diet would not have included tomatoes but may have included other ingredients that many of us would not consider healthy, but are in fact healthy for her," said study lead Eran Elinav in a release.
Elevated blood sugar is closely associated with chronic conditions like obesity, diabetes, and cardiovascular disease, and this study looked specifically at how certain foods affect blood sugar.
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The data showed that the glycemic index of food, long thought to be a fixed number, actually differs significantly from person to person, while a person's individual response to a specific food remained consistent from day to day.
"Measuring such a large cohort [they measured responses to over 45,000 meals] without any prejudice really enlightened us on how inaccurate we all were about one of the most basic concepts of our existence, which is what we eat and how we integrate nutrition into our daily life," said Elinav.
While it's unlikely that the new landscape of healthy eating will ever include Twinkies, the definition of "health food" is likely to become more nuanced. And personalized medicine will play a larger role in health maintenance.
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Another welcome change? The findings may help remove some of the stigma that comes with being overweight and diabetic.
"After seeing this data, I think about the possibility that maybe we're really conceptually wrong in our thinking about the obesity and diabetes epidemic," coauthor Eran Segal said in the release. "The intuition of people is that we know how to treat these conditions, and it's just that people are not listening and are eating out of control - but maybe people are actually compliant but in many cases we were giving them wrong advice."