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Comment by scoofy | Hacker News Reader

Whenever i read much of this anti-carb stuff, i'm always concerned about how different carbs affect the body. Taubes always blames the whole lot, but people like Lustig distinctly go after fructose. I get that carbohydrates probably affect the body in a negative light, but I certainly wish they would study sugars independently.

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Lustig goes after fructose but points out that fructose and sugar are metabolically equivalent. I believe he does so because fructose is more prevalent in processed foods (cheaper, subsidized, and other policy-driven historical accidents behind this).

Slight correction: sucrose (table sugar) and fructose are not metabolically equivalent.

There's an enzyme in your duodenum which cleaves the sucrose molecule into one fructose and one glucose molecule semi-instantly. In both cases, your body ends up with a bunch of fructose. However, if you're eating table sugar, only half of the resulting calories are from fructose; the rest are from glucose.

"Fructose" in Lustig's case is HFCS. HFCS is (depending on the formulation) ~45% - 85% fructose, with the remainder being glucose, and a typical formulation being close enough to 50-50 that it's a wash. Sucrose is a bound molecule, HFCS is free fructose + glucose molecules.

So, while there are some differences (and I suspect there actually are significant differences between HFCS and table sugar), for the most part, eating a lot of foods formulated with HFCS is very, very similar, metabolically, to eating a lot of foods formulated with table sugar.

Indeed. Carbs are not the same just as fats are not all the same. If you spend your life eating crisco and sugar your body will be affected in much different ways than if you spend your life eating olive oil and whole wheat, even if the quantities are identical.

that's not quite true. He implicates sugar more than anything as well, and has come around to that more and more over time. His next book is going to be about sugar. Part of the thinking is that while fructose may be causing a lot of problems, the fructose/glucose combination may be especially bad.

This is partially why the "glycemic index" is bogus.

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