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Thursday, June 5, 2014

Fructose alarm?

I came across an article on the science blogging site Science 2.0 stating that soda and juice companies are lying about fructose levels (that's pretty much the headline). It is a parsed summary of an accepted manuscript for the journal Nutrition which analyzes the fructose content of popular packaged beverages made with and without high fructose corn syrup. The article is critical enough to note that the fructose to metabolic syndrome connection is at best tenuous (and a poor approximation of real diets), but the charge that manufacturers are intentionally misleading customers with regards to fructose is bothersome.

To make the charge that someone is lying (or in this case, whole cadres of manufacturers - which only eggs on conspiracy theorists) is a fairly serious interpretation of the case. Does the evidence support this? The authors of the paper purchased samples of the different drinks, and analyzed them with various methods to measure the sugar composition of each sample. A bit of introductory chemistry here: glucose and fructose are simple sugars - when combined, the form sucrose, what we all call table sugar. More importantly, glucose and fructose are isomers - basically, they use the same atoms, but are just arranged differently. In fact, one can convert glucose to fructose and vice versa through a process called isomerization.

Corn syrup is mostly glucose. High fructose corn syrup (HFCS) is made by isomerizing part of that glucose into fructose - in fact, what makes HFCS "high fructose" is usually just 55% fructose to 45% glucose, rather than the 50-50 mix in regular table sugar. There are different grades of HFCS, depending on the amount of fructose therein.

So, the authors claimed that a significant portion of the sodas supposedly made with sucrose still contained free fructose, and that for a good portion of the sodas made with HFCS, the fructose was proportionally higher than the 55% that should be in the food grade HFCS. Does the data bear this out? Fortunately, the paper included the raw data, and I replotted it (after discovering a minor summation mistake in it).

Red circles denote drinks made with sucrose, blue are drinks made with HFCS. 
First of all, they only sample 4 drinks with sucrose. The drink types vary widely in flavor and formulation, but most cluster around the 55% mark - even those made with sucrose. But we also know that sucrose degrades into the simple sugars simply by heating it into syrup - so the fructose content could easily be a byproduct of the processing. The paper actually takes this possibility into consideration - but quickly discards it as unlikely, without reference and any further explanation. Reviewers should have picked up on this contention.

This does lend credence to the idea that by the time it gets to market, HFCS and sucrose are functionally identical. There is the one outlier - the Sierra Mist Natural which seems to retain much undegraded sucrose. It could be something peculiar with that manufacturer: seems to me that there is reasonable doubt here contend that the manufacturers that claim to use sucrose are actually secretly substituting HFCS just based on this evidence alone.

The other is that the drinks are higher than 55% proportion of fructose - a reasonable number of them are also below this magic 55% mark. This is within statistical deviation, and could be explained by simple manufacturing variation or even storage isomerization. But even if they are consistently higher than 55% - I don't think the drinks are labeled to disclose that they are at most 55% fructose. Only that they are made with HFCS - which they do disclose. After all, even at 75% fructose - it would still be called HFCS.

How does this support the contention that there is "lying" going on? This is a potentially libelous situation, as none of this supports evidence of the intent to mislead, or failure to disclose. At best, there is a hint that a manufacturer may be taking shortcuts, but it won't be from this kind of analysis.

Words such as "lying" carry weight. I should hope that science reporting will be more analytical, rather than parroting the frame that the authors of the study wish inject, to bring some kind of ominous implication of conspiracy based on flimsy evidence.

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