What’s good? What’s bad? How much sugar is too much? Here’s what the latest science says.
"There is no substitute for whole natural foods, a variety of foods, eaten in season. I read that xylitol, which is marketed as a natural sugar, is actually processed using toxic chemicals. "
“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).
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.