(P26-021-23) The Carbon Stable Isotope Ratio as an Objective Biomarker of Added Sugar Intake: A Scoping Review of Evidence in Human Nutrition

Objectives: Review evidence on the carbon stable isotope ratio (CIR) as a biomarker of added sugar (AS) intake and inform future directions in nutrition research.

Methods: A systematic scoping review was conducted. Studies in English that reported associations between CIR and AS intake (including total sugars, AS, and sugar-sweetened beverages (SSB)) were eligible.

Results: Search results yielded 4,387 studies; 26 articles were included, with earliest work published in 2010. Studies used observational (n=16) or controlled feeding (n=9) designs, and two studies examined dietary interventions (n=2). Eight studies included youth participants. Studies sampled blood (n=23), hair (n=5), and/or breath (n= 3). Most studies were conducted in two concentrated geographic regions (n=7 Virginia; n=6 Alaska) and only two studies were conducted outside the U.S. CIR measured in amino acids (n=4) showed that CIR-alanine in hair and blood provided the most robust evidence for CIR as a biomarker of AS intake. Studies examining breath CIR (n=3) also demonstrated positive associations with AS intake. Most of the remaining studies using hair or blood showed positive, but modest, associations with AS and SSB intake. Associations were generally stronger for SSB than AS intake. Associations varied by study design, dietary outcome of interest, dietary assessment instrument used (e.g., 24-hour recall vs. food frequency questionnaire), AS intake levels (high vs. low), and whether animal protein intake was considered (CIR is also associated with meat intake). Three studies demonstrated no association between CIR and AS intake; one study was conducted in an international sample and two in samples with low AS/SSB intake. Finally, studies demonstrated potential for CIR to capture short-term variation in sugar intake (n=3) and response to intervention (n=2).

Conclusions: Breath CIR and CIR of non-essential amino acids, namely alanine, show the strongest evidence as indicators of AS and SSB intake. The role of animal protein needs to be considered as it relates to the application of CIR, and more diverse samples should be included since underlying dietary patterns appear to influence the ability of CIR to reflect AS. Additionally, the potential for CIR to examine dietary intervention adherence and monitoring remains understudied.

Funding Sources: National Heart, Lung, and Blood Institute (NHLBI)