These words aren't from obscure researchers. In fact, Dr. Craig Thompson is president of Memorial Sloan-Kettering Cancer Center in NYC, one of the largest cancer hospitals in the world, and Dr. Lewis Cantley is the director of the Cancer Center at one of Harvard Medical School's hospital systems, and the quotes come from Mr. Gary Taubes' essay in the NY Times Magazine titled "Is Sugar Toxic?"
So, is sugar toxic? Depends. Like alcohol, refined sugar isn't toxic in small amounts. But lots of alcohol consumed every day for weeks on end is dangerous. So it is with refined sugar, whether we're talking sucrose (table sugar, which is roughly 50% glucose and 50% fructose) or high fructose corn syrup (HFCS, rough 55% fructose and the rest glucose), although the effects take longer to take root. The toxicity of sugar also depends on the person, as people respond differently.
Fructose, in contrast, doesn't cause the pancreas to release more insulin. But here's the thing. When the fructose load is high and fast, such as after drinking a can of Coca-Cola, it overwhelms the liver's ability to process it. Fructose is then broken down (or metabolized) and its parts used to make a fat molecule that's stored in the liver. If fructose hits the liver repeatedly, it becomes fatty. This is believed to give rise to insulin resistance.
Dr. Robert Lustig, a pediatric endocrinologist at UC-San Francisco, makes a convincing case that fructose in refined sugars is the worst part of modern diets, not glucose. By the way, there's fructose in fruits. But the fructose from fruit doesn't hit the bloodstream (and thus the liver) as hard as fast as fructose in refined foods like Starbucks pastries, and thus the "natural sugars" in fruits aren't as harmful. Here's Dr. Lustig's now-famous lecture on YouTube, made all the more popular by Mr. Taubes's essay.
Whether you blame glucose (which causes a rise in insulin) or fructose (which can cause the liver to become fatty), the underlying message is that refined sugars -- sucrose (table sugar) and HFCS -- are bad. Here's a telling sign: Sugar researchers themselves avoid eating table sugar, as the quotes at the beginning attest.
Note: Here's a Q&A with the Mr. Gary Taubes of the "Is Sugar Toxic?" essay. It's been eye-opening to learn how many people don't like to hear that sugar is bad for you.