Solving The Suger Puzzle (Part 2) - Sweet Choices

The Other Side of the Story

Lustig’s idea sounds appealingly logical, but many experts don’t buy his toxic-sugar theory. David Katz, M.D., M.P.H., is one such expert. He has written and spoken extensively on the subject. “That talk, what made it so viral was the extreme position,” says Katz, director of the Yale University Prevention Research Center and an EatingWell advisor. “Vilifying a certain nutrient is a good-versus-evil worldview. It’s easy to get people excited if you say the most extreme thing.”

ABC News Nightline correspondent John Donvan interviews pediatric endocrinologist Robert Lustig about the dangers of consuming fructose

Though Lustig is a respected physician, he isn’t a fructose researcher (he has only one original scientific paper on the subject, based on government-generated not lab-generated data). Most of his 90-plus published scientific papers focus on overweight children. And before his infamous lecture, only two mentioned fructose at all; since 2009, he’s published six papers that mention fructose, mostly editorials, reviews and commentaries on his theory.

But he’s not the only one to theorize that fructose is causing some of our modern health problems. In 2004, George Bray, M.D., at the Pennington Biomedical Research Center in Louisiana, and Barry Popkin, Ph.D., at the University of North Carolina at Chapel Hill, noticed that rising rates of obesity paralleled an increase in sugar consumption and they loosely attributed this to the harmful way our body metabolizes fructose. Other studies have since more strongly linked consuming sugar-sweetened beverages like sodas and juices with obesity, at least in children and adolescents, and for years researchers have been giving animals extremely high doses of fructose to create metabolic syndrome.

Why, then, is Lustig famous for the theory?

“Lustig takes a very evangelical and sensational approach to the data,” says John Sievenpiper, M.D., Ph.D., a researcher at St. Michael’s Hospital and McMaster University in Ontario who has analyzed many of the fructose studies; he comes to a conclusion that is the opposite of Lustig’s. “He puts up these really wonderful, very seductive models. But, really, they’re just hypotheses.”

Hypotheses are unproven ideas that scientists can test, and many scientists have already tested whether consuming a lot of fructose alters the cholesterol and fats in the blood, the fats in the liver, blood pressure. Data from animal models, on which Lustig’s hypothesis is firmly based, is clear: when animals consume very high levels of fructose, say, 60 percent of their calories, they do seem to have the symptoms of metabolic syndrome: high levels of triglycerides in their blood, high blood pressure, insulin resistance and weight gain.

But, say Sievenpiper and others, there are obvious problems with transposing animal experiments to human health: in animal studies, the researchers give the animals three times more than the highest amount of fructose most humans ever eat. Plus, animals process carbohydrates very differently from humans (their livers are naturally geared to make fat from carbohydrate).

daily consuming one (or more) sugar sweetened beverages, which also contain a lot of fructose, raises risk of heart disease.

In addition, human studies, at this point, don’t even all point to the same answer. Supporting Lustig’s theory are a few epidemiological studies (these studies follow large groups of people over time) that show increased health risks for people who frequently consume drinks high in sugars. The Nurses Health Study, one of the biggest epidemiological studies around, found that drinking a small glass of fruit juice daily (full of fructose) is associated with higher incidence of type 2 diabetes; daily consuming one (or more) sugar-sweetened beverages, which also contain a lot of fructose, raises risk of heart disease. The Framingham Heart Study showed that people who drank more than a can of soda a day were more likely to have metabolic syndrome.

Sweet Choices

Confused in the sugar aisle? Use this handy comparison chart to help you decide which sweetener to choose and how to use it.