A friend just forwarded the new Gary Taubes NYT Magazine article on Robert Lustig’s claims that sugar is “toxic.” It’s an interesting article, worth a read, and Taubes is reasonably circumspect in acknowledging the uncertainties in the current evidence. He starts with this acknowledgment:
The viral success of [Lustig's] 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.”[...]
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.
Indeed, that’s precisely what’s at issue with Lustig’s lecture: not whether sugar is a problem, but whether it’s the problem. And to make that case, Taubes stacks the deck with statements like this:
The conventional wisdom has long been that the worst that can be said about sugars of any kind is that they cause tooth decay and represent “empty calories” that we eat in excess because they taste so good.
Who the heck claims this? (In journalistic jargon, phrases like “The conventional wisdom has long been…” are known as “weasel words,” because they allow you to make statements that help your argument without finding anyone stupid enough to actually say them.) It’s a convenient distortion, because it lends some misplaced novelty to the “Men Land on the Moon!” discussion that follows, about the links between sugar and metabolic syndrome. Come on, we’ve been talking about “glycemic index,” in which glucose is assigned the nominal maximum value, since the early 1980s. This is an important topic, and perhaps one that not everyone fully appreciates, but it’s tangential to Lustig’s central claim that sugar (and fructose in particular) is a “toxin.”
The central question here is really about dose. Is sugar “unsafe at any dose,” as Ralph Nader might put it? Or is it only unsafe when consumed to excess? And if the latter, what constitutes “excess”? To his credit, Taubes makes this point, though he weakens it by putting it in the mouth of someone he identifies as a lobbyist for the corn refining industry:
[S]ugar and high-fructose corn syrup might be toxic, as Lustig argues, but so might any substance if it’s consumed in ways or in quantities that are unnatural for humans. The question is always at what dose does a substance go from being harmless to harmful? How much do we have to consume before this happens?
Much of the rest of Taubes’s article explores how much sugar we’re now eating, how much it has increased, and how diseases like diabetes and cancer have increased in parallel. It makes a strong case for eating less added sugar — pretty much exactly the same case that Taubes made in his 2007 book Good Calories, Bad Calories, as far as I can tell. Heck, I was convinced in 2007, and I’ve been very conscious of my sugar intake — along with other highly refined carbohydrates — ever since then. What I don’t see here is any reason to be more scared of sugar than I was before on the basis of Lustig’s “sugar is a toxin” argument.
Taubes describes the mechanism of fructose’s action as follows:
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…
Again, scary stuff. But how is this different from, say, glucose, or even refined carbs from white bread, which are thought to stimulate insulin resistance if they enter the body “in sufficient quantity and with sufficient speed”? If we’re concluding that fructose is “toxic,” shouldn’t we also conclude that glucose and white bread and all other refined carbs are too? Oh wait, that’s what Gary Taubes proposed in 2007. So what has Lustig added? Fructose causes the same problems as other foods, but through a different biochemical pathway.
What would get my attention is evidence that cumulative exposure to fructose — independent of the rate of intake — accumulates over time to produce problems. In other words, does eating 50 pounds of sugar spread out over 30 years ultimately produce essentially the same bad effects as eating 50 pounds of sugar in a single year? Or is it only a problem when the dose comes “in sufficient quantity and with sufficient speed”?
To be clear, I have no doubt whatsoever that Lustig is right that we eat too much sugar and it’s causing health problems. I just wonder if there’s actually anyone in the country who didn’t already think that.