Eating fruit is healthy, right? After all, is there any food that’s more synonymous with health than the apple? Fruit in general is always looked upon as the epitome of healthy eating. But new research says fructose—the sugar found in fruits—may actually lead us to crave higher calorie foods.
The study, published in the recent issue of the journal PNAS, looked at brain activity in 24 volunteers, comparing the brain reactions to consuming either glucose or fructose (fructose is also found in honey and in high-fructose corn syrup).
And according to the study results, the consumption of fructose increased the responses to images of food and “a tendency to choose eating a high-calorie food over a future monetary reward,” reports the New York Times.
The study subjects consumed ten ounces of a cherry-flavored liquid that contained either two and a half ounces of fructose or glucose. The researchers tested blood samples to measure the levels of fructose or glucose as well as the levels of insulin and enzymes used in signaling to the brain satiety or hunger (enzymes called leptin and ghrelin).
“Before having their drinks, the participants rated their desire to eat on a one-to-10 scale from ‘not at all’ to ‘very much.’ Then they drank the liquids and had functional magnetic resonance imaging brain scans while looking at images of food and of neutral objects like buildings or baskets,” reports the Times. “As they did so, they rated their hunger using the scale. The volunteers were then presented with images of high-calorie foods and asked whether they would like to have the food now, or a monetary award a month later instead.”
Compared to glucose, consumption of fructose “produced greater responses to food cues in the orbital frontal cortex of the brain, a region that plays an important role in reward processing,” the Times explains. “The fructose drink also produced greater activity in the visual cortex when volunteers looked at images of food, a finding that suggests increased craving compared with glucose.”
While the enzymes leptin and ghrelin were the same in fructose and glucose groups, the insulin response was significantly lower in the fructose group—which may impact our food choices, according to study author Dr. Kathleen Page, assistant professor of clinical medicine at the Keck School of Medicine of the University of Southern California.
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“Insulin is released when we consume glucose,” she said. “The pancreas secretes insulin, and insulin drives glucose into cells so that it can be used for energy. But it also sends a signal to the brain that says ‘you’ve eaten.’ Fructose doesn’t stimulate insulin secretion, and if there’s no insulin, you don’t get the information that you’re full.”
But Dr. Page says it doesn’t mean people should stop consuming fruit—it’s still a healthier choice than processed foods. But do beware of fructose-sweetened foods and beverages, which may be more likely to cause problems.
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Fruit image via Shutterstock