A recent clinical trial published in Oxford University’s Journal of Nutrition identified a biomarker that researchers believe accurately represents a person’s added sugars intake, based on the results of a controlled feeding study.
 
The biomarker, called the carbon isotope ration (CIR) was initially proposed as a biomarker for added sugars intake, however, a CIR is also associated with meat intake. It has been proposed, however, that the CIR of amino acids has the potential to differentiate sugars from meat intakes, because essential amino acids must be derived from dietary protein, whereas some nonessential amino acids can be synthesized from sugars.
 
In a study of 145 postmenopausal women, participants were observed to determine if serum CIRS of amino acids could meet a prespecified biomarker standard for determining added sugars intake. The participants were administered individualized diets that approximated their habitual food intakes for two weeks, and it was found that added sugars consumption correlated with alanine, one of seven amino acids accounted for during a gas chromatography test over the duration of the trial.
 
It was found that a model of added sugars intake based on serum levels of carbon isotope ratios alanine, glycine, isoleucine, smoking, physical activity, and bodyweight met a biomarker criterion, which was R² = 0.37.
 
“The carbon isotope ratio has potential as a biomarker of AS intake because it is elevated in corn and sugar cane, which supply 70% of caloric sweeteners and nearly all sugar-sweetened beverages in the United States,” the authors wrote. “However, due to the widespread use of corn to feed livestock in the United States, the CIR is also associated with meat and/or animal protein, often more strongly than with added sugars or sugar-sweetened beverages. The consistent association of the CIR with animal protein/meat intake is a major limitation of the CIR as a candidate biomarker for AS.”
 
To make the isotope biomarker of added sugars more stable, the CIR of a suite of molecules was shown through statistical analysis to be a sufficient biomarker when taking into account the lifestyle characteristics of participants. They reported that a factor contributing to the validation of this dietary biomarker was “robustness” – it performed in similar ways across different diets and settings. The authors also proposed that CIR could be used as a biomarker for added sugars intake in conjunction with a 24-hour spot urine sample of fructose and sucrose as metabolites.
 
“Further evaluations are needed in U.S. populations, including those with greater variability in added sugars intake and in more diverse populations,” the authors concluded (most of the 145 participants were white postmenopausal women). “These findings highlight the potential for CIR of serum amino acids to provide an objective biomarker for added sugars intake in U.S. populations, and ultimately help to clarify associations with chronic disease risk.”