Study Shows Sharp Differences With Introduction, Withdrawal of Fructose

Patients on a high-fructose diet showed increases in conversion of sugar to fat, reduction of conversion of fat and an increase in liver fat, according to results released this week of a pilot study by researchers at UC-San Francisco and Touro University California in Vallejo.

The same patients exhibited a reversal of that pattern when switched off the high-fructose diet, researchers said — in just nine days for each diet.

“Nine days is not a lot of time to see differences,” said study lead investigator Jean-Marc Schwarz of Touro University California. “It says something that you see the effects so quickly — and the recovery [from those effects] so quickly.”

Schwarz said one of the purposes of the study was to isolate high-fructose products, because other research has suggested that overeating might be a contributing factor.

A bill in the state Legislature proposes health warning labels on sodas and energy drinks sold in California. Schwarz said fruit juices have a similar level of fructose to those drinks. “I’m not a policy person,” he said. “To me, it’s really the same thing.”

Researchers said they will expand the research to explore the impact of fructose restriction on obese children.

In the pilot study, adults stayed in a research ward at San Francisco General Hospital, and their diets were controlled and monitored over 18 days. In the first nine days, a certain number of calories were filled with fructose; in the second nine days, those calories were swapped out for the same exact number of calories in complex carbohydrates.

Not only did patients show a striking change between the two diets, Schwarz said, but all of the patients showed those changes.

“That was the big surprise to us,” he said. “What was very surprising is that every subject showed changes in the same way, they were all doing the same thing. You have every single subject showing an increase in converting sugar to fat, a reduction of the conversion of fat and an increase in liver fat.”

And he saw a mirror image of those changes in the second nine days, as their bodies recovered from the bursts of fructose, Schwarz said.

He said drinks with high-fructose corn syrup and high fructose in general can tax the liver with too much sugar.

“I call it the tsunami effect. It’s this sort of uncontrolled wave,” Schwarz said. “It’s a maverick of sugar, and that’s going to shock your liver.”

With fruit, he said, the fiber delays the absorption. But with juices, there’s more quantity of fructose, delivered in a concentrated way.

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