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I've been saying for ages that the sugar composition of high-fructose corn syrup (HFCS) is no different from that of table sugar (sucrose).

Oops. A new study in the journal Obesity actually measured the amounts and kinds of sugars in 23 kinds of HFCS-sweetened drinks (click here for the PDF).

The findings are summarized in a fact sheet (PDF):

    • The sugar content varied widely from amounts stated on labels. Some drinks had 15 percent less sugar than labeled, but others had as much as 30 percent more.

    • On average, the drinks had 18 percent more fructose than expected.

    • Several brands of sodas seemed to be made with HFCS that is 65 percent fructose, not 55 percent.

    • The average amount of fructose in the drinks was 59 percent.

The press release (full PDF here) points out one other finding. You know how everyone thinks Mexican Coca-Cola is so much more delicious than American Coke because it is made with table sugar (sucrose), not HFCS? Oops again. The investigators could not find any sucrose in the Coke, but did find plenty of glucose and fructose. This suggests that Mexican Coke is also made with HFCS (or it could also mean that the sucrose had been split into its constituent glucose and fructose).

To review the biochemistry: Sucrose is a double sugar of glucose and fructose bonded together. HFCS is glucose and fructose, separated. The sucrose bond is quickly split in the intestine and its glucose and fructose are the same as those in HFCS.

The metabolic problems that result from sugar intake are mostly due to the fructose content. Less is better for health. More is better for the soft drink industry, however. Fructose is sweeter than either glucose or sucrose, and sweetness is what sells sodas.

At most, HFCS is supposed to be 55 percent fructose, as compared to the 50 percent in table sugar. Most foods and drinks are supposed to be using HFCS that is 42 percent fructose. A percentage of 55 is not much different biologically than 50, which is why the assumption has been that there is no biologically meaningful difference between HFCS and table sugar. This study, if confirmed, means that this supposition may need some rethinking.

The study names the beverages that contain 65 percent fructose: Coke, Pepsi, Sprite. It identifies Dr. Pepper, Gatorade, and Arizona Iced Tea as containing close to 60 percent fructose.

If, in fact, the percentage of fructose is higher than advertised, it's another good reason to avoid sugar-sweetened beverages.

This post also appears on foodpolitics.com.