"Telling people the problem is all fructose is completely wrong," says Walter Willett, chair of the nutrition department at the Harvard School of Public Health. "In the amounts being consumed, sugar can lead to serious damage and premature death. I think it's fair to say that's toxic," he says. "But it doesn't mean everything else is good."
Read Lustig's book carefully, and it's clear that his position isn't as radical as his sound bite implies: He believes that moderate consumption of fructose is safe. The "likely" safe threshold, he says, is 50 grams per day — which translates to 100 grams, or a quarter-cup, of sugar that's half fructose. Average daily American consumption of added sweeteners, according to the USDA, is 95 grams — just under Lustig's threshold.