Response to the “Letter to the Editor by LJ Hobbs”
Version of Record online: 6 SEP 2012
2011 North American Association for the Study of Obesity (NAASO)
Volume 19, Issue 4, pages 687–688, April 2011
How to Cite
Goran, M. I., Ventura, E. E. and Davis, J. N. (2011), Response to the “Letter to the Editor by LJ Hobbs”. Obesity, 19: 687–688. doi: 10.1038/oby.2011.37
- Issue online: 6 SEP 2012
- Version of Record online: 6 SEP 2012
TO THE EDITOR: We are pleased to respond to the letter to the editor entitled “Response to ‘Sugar Content of Popular Sweetened Beverages Based on Objective Laboratory Analysis: Focus on the Fructose Content'” from Larry Hobbs (1), Executive Director of the International Society of Beverage Technologists, relating to our recent paper. This letter points out a possible methodological limitation of our study and that high fructose corn syrup (HFCS) is not a simple mixture of glucose and fructose. This letter is therefore helpful in correcting a commonly held assumption and clarifies that HFCS is a complex mixture of mono-, di-, and oligo-saccharides, and may contain up to 5% complex oligosaccharides as well as other sugars such as maltose. Since we did not specifically measure these sugars, our estimates of total sugar content may actually be underestimated. In addition, we are not disputing the sugar composition of HFCS but rather we are questioning the sugar composition of popular drinks in terms of gaining more insight into the sugar content of what is actually consumed.
However, since the method we used (Association of Analytical Communities (AOAC) 977.20) was specific for assaying glucose, fructose, and sucrose (and was verified for this purpose through the use of external blinded standards), we are unsure how our results could have overestimated the fructose content or the fructose:glucose ratio. The letter by Hobbs suggests that the presence of maltose was falsely detected, specifically as fructose, by our methodology, but this seems unlikely given the chemical/structural differences between fructose and maltose, and an assertion that was not directly tested. A much better comparison would have been to assay blinded standards and beverage samples by the two methods to see how the results would compare. Regardless of potential methodological limitations of the AOAC 977.20 method, our results still point to a potentially higher level of fructose in some popular beverages. For example, according to the findings of the Hobbs letter, a HFCS of 55% fructose tested at 58% using AOAC 977.20, suggesting that our method may have slightly overestimated fructose content. In contrast, we found that three of the major soft drink brands we tested had a fructose:glucose mixture in the ratio of 65:35, still much higher than would be expected even accounting for a possible overestimation of fructose. Given the very close chemical structures of fructose and glucose it seems unlikely that any methodological overestimation of sugars due to presence of maltose or other disaacharides, would be falsely detected only as fructose as asserted in the letter.
We certainly acknowledge that our results are exploratory and should be used as a starting point for future research. A more detailed and thorough analysis is required. Future studies should use the most sophisticated assay methods possible since both of the methods in discussion (AOAC 977.20 and AOAC 979.23) have limitations and could be improved upon for greater specificity. In addition, future studies should determine the influence of factors such as batch differences, storage, and where the product was made on sugar content and composition. Taken together, our study and the letter from Hobbs point to a common need for more detailed labeling of products in terms of sugar composition (including disclosure of fructose content) and more disclosure from the corn syrup industry regarding type of HFCS used as well as HFCS composition. These requirements can only be helpful to the research community as well as to consumers.