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‘Healthy’ Foods May Be Better for Some People Than Others

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People with diabetes have long known that the same food can affect different people’s blood sugar differently. Now, for the first time, there’s scientific proof: Scientists report that a food’s effect on blood sugar depends not just on the food, but on the person eating it.

Blood glucose, commonly known as blood sugar, may be best known for its association with diabetes, but it’s important for everyone to understand. Glucose travels through your bloodstream, delivering energy to every part of your body. Every time you eat, your blood sugar jumps up. Scientists call this jump a postprandial glycemic response (PPGR).

There are two popular methods for predicting how a given food will affect a person’s PPGR: the number of carbs in a food and the glycemic index. Both strategies assume that a food creates the same PPGR response no matter how it’s eaten—or who eats it.

That assumption may be flawed, says a team of researchers from Israel’s Weizmann Institute. Their new report, published last week in the journal Cell, argues that universal guidelines may actually be encouraging people to eat foods that make their blood sugar worse.

“Ascribing a single PPGR to each food … assumes that the response is solely an intrinsic property of the food,” study co-author Eran Segal told The Atlantic. “But there are very striking differences between people's responses to identical meals.” 

Segal and his colleagues recruited 800 healthy volunteers and gave them questionnaires on their eating habits and medical histories. The volunteers provided stool samples so the researchers could check out their gut bacteria. For one week, they tracked their meals and sleep using a mobile app, while a continuous glucose monitor measured their blood sugar. Everyone ate the same breakfast, but beyond that, what they ate was completely up to them. 

Studying people’s eating habits can be tricky, especially when the data is self-reported. People tend to slack or fudge the numbers when tracking their food. That wasn’t a problem for this experiment, Segal told The Atlantic. These volunteers were motivated: “They joined because we explained that we'd be able to tell them which of the foods they normally eat spike their glucose levels. They came because they wanted to know and we said that if they didn't log properly, we wouldn't be able to tell them.”

The results were dramatic, and completely unique to each volunteer. Foods that caused PPRG spikes in one person had little to no effect on another. The data showed that what and how much you eat matters, of course, but just how it matters varies immensely.

These results weren’t limited to high-carb junk food. One middle-aged woman was working hard to stick to a healthy diet that included lots of vegetables, including tomatoes. But data from her glucose monitor showed that her blood sugar spiked each time she ate tomatoes. The good-for-you produce wasn’t good for her at all.

The researchers’ next step was to turn their results into an algorithm. They recruited a fresh round of volunteers and provided each one with two customized meal plans: one “good” and one “bad.” Half of the meal plans came from nutrition experts, and the other half were generated by the algorithm.

Sure enough, the volunteers’ PPRGs improved during the “good” week—even though each person was eating something different. Even their gut bacteria changed for the better. This was true of both the man-made meal plans and those suggested by the computer; in fact, the algorithm's customized recommendations were slightly more effective than those made by the experts.

The researchers hope their results will inspire a new approach to nutrition and weight management. Co-author Eran Elinav said in a press release that the study "really enlightened us on how inaccurate we all were about one of the most basic concepts of our existence, which is how we eat and how we integrate nutrition into our daily life."

Our scientific and cultural approaches to obesity and diabetes may just be “really conceptually wrong,” he said. Scientists and medical professionals believe “we know how to treat these conditions, and it's just that people are not listening and are eating out of control," Segal said, "but maybe people are actually compliant and in many cases we were giving them the wrong advice."

Other researchers believe it may be too early to draw such strong conclusions, and note that Elinav, Segal, and their colleagues never directly compared their results to the glycemic index.

Still, these findings are making waves. The team won’t have any trouble finding volunteers for their next experiment; the wait list currently includes more than 4000 people.

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Food
Researchers Pinpoint the Genes Behind the Durian's Foul Stench
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Durian is a popular fruit in parts of southeast Asia. It's also known for having the most putrid, off-putting odor of any item sold in the produce section. Even fans of durian know why the fruit gets a bad rap, but what exactly causes its divisive scent is less obvious. Determined to find the answer, a team of researchers funded by "a group of anonymous durian lovers" mapped the fruit's genome, as reported by the BBC.

The study, published in the journal Nature Genetics [PDF], contains data from the first-ever complete genetic mapping of a durian fruit. It confirms that durian's excess stinkiness comes from sulfur, a chemical element whose scent is often compared to that of rotten eggs.

Analysis of the fruit's chemical makeup has been done in the past, so the idea that sulfur is a major contributor to its signature smell is nothing new. What is new is the identification of the specific class of sulfur-producing genes. These genes pump out sulfur at a "turbocharged" rate, which explains why the stench is powerful enough to have durian banned in some public areas. It may seem like the smell is a defense mechanism to ward off predators, but the study authors write that it's meant to have the opposite effect. According to the paper, "it is possible that linking odor and ripening may provide an evolutionary advantage for durian in facilitating fruit dispersal." In other words, the scent attracts hungry primates that help spread the seeds of ripe durian fruits by consuming them.

The revelation opens the door to genetically modified durian that are tweaked to produce less sulfur and therefore have a milder taste and smell. But such a product would likely inspire outrage from the food's passionate fans. While the flavor profile has been compared to rotten garbage and dead animal meat, it's also been praised for its "overtones of hazelnut, apricot, caramelized banana, and egg custard" by those who appreciate its unique character.

[h/t BBC]

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Big Questions
What Is Pumpkin Spice?
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Pumpkin Spice season seems to come earlier every year, but today marks its official arrival, as October 1 is National Pumpkin Spice Day. Before you reach for a cup, drink this in: The flavor can be composed of more than 300 elements—and pumpkin isn’t one of them.

Most recipes include cinnamon, nutmeg, allspice, ginger, and vanilla, but not every incarnation of the concoction is the same, according to a video by food scientist and spokesperson for The Institute of Food Technologists, Kantha Shelke, Ph.D, C.F.S.

So what’s the connection to the season’s most beloved orange fruit? (Yes, pumpkin is a fruit!) Flavor companies also add in skillfully designed compounds that mimic the taste of pumpkin pie. Each chemical is carefully reviewed by the U.S. Food and Drug Administration and approved at concentrations of about 20 to 50 times the normal consumption level. And even though the full flavor contains 340 compounds, combining only five to 10 percent of those molecules in a mix is enough to trick our brains into thinking, “Mmm, just like Thanksgiving!”

But beware: attempting to recreate the magic in the average kitchen isn't as easy as pie. With only the spices available at a supermarket, the final product will likely taste more like Chai than the seasonal treat on professional menus. “Pumpkin Spice isn’t set in stone,” Shelke says. “Everyone has their secret recipe.”

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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