Is Sugar Toxic?

Introduction (via Gary Taubes)

On May 26, 2009, Robert Lustig gave a lecture called “Sugar: The Bitter Truth,” which was posted on YouTube the following July. Since then, it has been viewed well over 800,000 times, gaining new viewers at a rate of about 50,000 per month, fairly remarkable numbers for a 90-minute discussion of the nuances of fructose biochemistry and human physiology.

Lustig is a specialist on pediatric hormone disorders and the leading expert in childhood obesity at the University of California, San Francisco, School of Medicine, which is one of the best medical schools in the country. He published his first paper on childhood obesity a dozen years ago, and he has been treating patients and doing research on the disorder ever since.

The viral success of his lecture, though, has little to do with Lustig’s impressive credentials and far more with the persuasive case he makes that sugar is a “toxin” or a “poison,” terms he uses together 13 times through the course of the lecture, in addition to the five references to sugar as merely “evil.” And by “sugar,” Lustig means not only the white granulated stuff that we put in coffee and sprinkle on cereal — technically known as sucrose — but also high-fructose corn syrup, which has already become without Lustig’s help what he calls “the most demonized additive known to man.”

It doesn’t hurt Lustig’s cause that he is a compelling public speaker. His critics argue that what makes him compelling is his practice of taking suggestive evidence and insisting that it’s incontrovertible. Lustig certainly doesn’t dabble in shades of gray. Sugar is not just an empty calorie, he says; its effect on us is much more insidious. “It’s not about the calories,” he says. “It has nothing to do with the calories. It’s a poison by itself.”

If Lustig is right, then our excessive consumption of sugar is the primary reason that the numbers of obese and diabetic Americans have skyrocketed in the past 30 years. But his argument implies more than that. If Lustig is right, it would mean that sugar is also the likely dietary cause of several other chronic ailments widely considered to be diseases of Western lifestyles — heart disease, hypertension and many common cancers among them.

The number of viewers Lustig has attracted suggests that people are paying attention to his argument. When I set out to interview public health authorities and researchers for this article, they would often initiate the interview with some variation of the comment “surely you’ve spoken to Robert Lustig,” not because Lustig has done any of the key research on sugar himself, which he hasn’t, but because he’s willing to insist publicly and unambiguously, when most researchers are not, that sugar is a toxic substance that people abuse. In Lustig’s view, sugar should be thought of, like cigarettes and alcohol, as something that’s killing us.

This brings us to the salient question: Can sugar possibly be as bad as Lustig says it is?

Fascinating Excerpt (via Gary Taubes)

The phrase Lustig uses when he describes this concept is “isocaloric but not isometabolic.” This means we can eat 100 calories of glucose (from a potato or bread or other starch) or 100 calories of sugar (half glucose and half fructose), and they will be metabolized differently and have a different effect on the body. The calories are the same, but the metabolic consequences are quite different.

The fructose component of sugar and H.F.C.S. is metabolized primarily by the liver, while the glucose from sugar and starches is metabolized by every cell in the body. Consuming sugar (fructose and glucose) means more work for the liver than if you consumed the same number of calories of starch (glucose). And if you take that sugar in liquid form — soda or fruit juices — the fructose and glucose will hit the liver more quickly than if you consume them, say, in an apple (or several apples, to get what researchers would call the equivalent dose of sugar). The speed with which the liver has to do its work will also affect how it metabolizes the fructose and glucose.

In animals, or at least in laboratory rats and mice, it’s clear that if the fructose hits the liver in sufficient quantity and with sufficient speed, the liver will convert much of it to fat. This apparently induces a condition known as insulin resistance, which is now considered the fundamental problem in obesity, and the underlying defect in heart disease and in the type of diabetes, type 2, that is common to obese and overweight individuals. It might also be the underlying defect in many cancers.

When Glinsmann and his F.D.A. co-authors decided no conclusive evidence demonstrated harm at the levels of sugar then being consumed, they estimated those levels at 40 pounds per person per year beyond what we might get naturally in fruits and vegetables — 40 pounds per person per year of “added sugars” as nutritionists now call them. This is 200 calories per day of sugar, which is less than the amount in a can and a half of Coca-Cola or two cups of apple juice. If that’s indeed all we consume, most nutritionists today would be delighted, including Lustig.

But 40 pounds per year happened to be 35 pounds less than what Department of Agriculture analysts said we were consuming at the time — 75 pounds per person per year — and the U.S.D.A. estimates are typically considered to be the most reliable. By the early 2000s, according to the U.S.D.A., we had increased our consumption to more than 90 pounds per person per year.

That this increase happened to coincide with the current epidemics of obesity and diabetes is one reason that it’s tempting to blame sugars — sucrose and high-fructose corn syrup — for the problem. In 1980, roughly one in seven Americans was obese, and almost six million were diabetic, and the obesity rates, at least, hadn’t changed significantly in the 20 years previously. By the early 2000s, when sugar consumption peaked, one in every three Americans was obese, and 14 million were diabetic.

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13. April 2011 by Miguel Barbosa
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