Optimising nuclear techniques to assess accurate quantitative biomarkers of added sugar intake in adults

The proposed CRP will contribute to a better understanding of the appropriate use of natural abundance stable isotope ratios of carbon (13C/12C, hereafter the “CIR”) to develop a biomarker to assess free sugar intake in different populations. This is relevant in terms of the emerging evidence for the role of carbohydrate and free sugar intake in chronic disease, and the recent WHO guidelines which recommend restricting free sugar in the diet to less than 5% of total energy intake.
In many countries, the intake of refined carbohydrates and cane sugar is high in both adults and children. A biomarker of, for example, cane sugar intake, could offer very useful information in dietary surveys. It would allow to assess the association of added sugars with chronic disease, within the framework of body fat accumulation. However, it has become clear in recent years, based on comparisons with the few established dietary intake biomarkers, that available self reported dietary assessment approaches have limitations. Objective biochemical measurements provide a useful approach to characterizing dietary exposures; however, to be acceptable for scientific use, the objective measure must provide a suitably accurate estimate of intake variation in study populations. 
The natural abundance carbon isotope ratio (CIR, 13C/12C) has great potential as a biomarker for sugar intake due to the elevated CIR characteristic of sugar cane. Worldwide, there are many countries for which cane sugar is the predominant source of free sugars and for which corn is not a major component of either processed foods or animal feeds. In those countries, the CIR is likely to have higher validity and specificity as a biomarker of free sugar intake. The specificity of the CIR for free sugar intake can be improved when it is measured in molecules that favour the incorporation of glucose carbon, such as the amino acid alanine (CIR-ala). Studies in the USA have confirmed that CIR-ala has improved validity and specificity for free sugars/sugar sweetened beverage intake when compared with total CIR. However, measurement of CIR-ala is considerably more expensive and time consuming than measurement of total CIR. Whether those additional costs are justified depends on the relative performance of total CIR and CIR-ala as biomarkers of free sugars in a given population. This is unknown for populations outside the USA.
This CRP aims at testing the utility of total CIR and if additional funding becomes available CIR-ala as biomarkers of free sugar intake in adults, and to identify and gain knowledge of interfering dietary practices and other limitations. Therefore, adults from different populations outside the USA with different dietary background, including those who eat corn, millet or sorghum as a staple, will be assessed by comparing the biomarker with accurate measurements of the daily added sugar intake. The Doubly Labelled Water method will be used to validate the accuracy of the dietary recalls.