May 12, 2009 7:36 pm US/Pacific
Sugar Molecule Linked to Liver Damage
(CBS 5)
This is Part 2 of Dr. Kim Mulvihill's series on sugar. Click for:
Part 1: The Bittersweet Truth About Sugar
Part 3: How Sugar Hijacks Your Brain
Part 4: Waging War on Sugar to Win the Battle of the Bulge
Part 5: Experts Weigh In On Stopping the Obesity Crisis
Part 2:
Foie gras is french for fatty liver. The delicacy, often sold as pate, is made when ducks or geese are force fed, causing their livers to fatten up as much as twelve times the normal size. However, what's shoved down their throats is not fat, but corn.
Pediatric endocrinologist Dr. Robert Lustig of U.C. San Francisco Medical Center says he's starting to see fatty livers that look just like foie gras, but not in ducks or fancy restaurants. He's seeing them in the bodies of overweight and obese children.
"If you look at a kid's fatty liver, it looks just like pate," Dr. Lustig explains. "It's just got this glisteny white look to it, and you know it's not normal."
Fatty liver disease can lead to cirrhosis, liver failure, even death. At UCSF, surgeons have already performed liver transplants on two obese 15-year-olds. Dr. Lustig says these kids are different from than the geese in one regard.
"Instead of being force fed like the geese, they self-fed the carbohydrate in the soda," he says.
The carbohydrate in the soda are sugars and sweeteners. Dr. Lustig says the boys drank a lot of sugary beverages. What hurt their livers was not just excess calories, he says, but excess amounts of a molecule called fructose.
And the trouble in the liver is causing another problem called Acanthosis Nigricans, or a hyperpigmentation and thickening of the skin. Dr. Lustig explains acanthosis in overweight or obese children is a sign of excessive insulin, which he says is a precursor in many cases to diabetes.
Fructose is found naturally in fruits and vegetables. But it's also found in many sugars, from cane and beet to high fructose corn syrup. Dr. Lustig says excessive amounts of dietary fructose is a problem and that it doesn't matter if the sugar comes out of the ground or is made in a factory. He points out sugars and sweeteners used in processed foods are half fructose and it's the fructose which is the problem.
A century ago, Americans ate roughly three teaspoons of fructose a day, mainly from produce. Today, we eat five times that amount, or about 17 teaspoons of fructose a day. Most of that comes from processed foods and beverages. The main sources are sugary drinks, baked goods, cereals, snacks, and fruit juices.
And growing evidence suggests consuming too much fructose over time is harmful. In a new study published in April, adults fed fructose-sweetened beverages for just ten weeks gained toxic belly fat, boosted triglycerides, and became more insulin resistant.
Dr. Lustig explains our livers just can't handle the onslaught of too much fructose, that the liver turns the sugar into fat. The sugar and sweetener industries take issue with the research. The Sugar Association says the fructose in table sugar is biologically distinct from other forms of fructose. The Corn Refiners Association says these experiments used one hundred percent pure fructose and that since we don't eat 100 percent pure fructose in our diets, these fructose studies are totally irrelevant to human nutrition.
Cardiologist Dr. James Rippe speaks for the Corn Refiners Association. He says both table sugar and high fructose corn syrup are only 50% fructose.
"It's very unfortunate that people are doing these pure fructose experiments and then confusing the public to say 'Well, gee if pure fructose is bad, high fructose corn syrup must be bad,'" Dr. Rippe explains.
But these industries have another complaint: that these studies will discourage Americans from eating fruits and vegetables. Dr. Rippe explains that it's important to remember another source of fructose in the diet is fruit.
"Do we really want people to be afraid of consuming fruit?" he asks.
Dr. Lustig responds that there no reason to fear eating whole fruits and veggies. Unlike processed foods, he says, fruits and veggies have fiber. And fiber slows the absorption of fructose, so the liver can handle it. Dr. Lustig calls fiber "nature's antidote" to fructose, saying whenever there is fructose in nature, you will find way more fiber.
Think of fiber as one antidote. The other is exercise. That's because with fructose, you have two choices: either burn it off with exercise or metabolize it in your liver.
That's why the Michael Phelps of the world can eat 12,000 calories a day.
(© MMIX, CBS Broadcasting Inc. All Rights Reserved.)
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