A Dual-Carbon-and-Nitrogen Stable Isotope Ratio Model Is Not Superior to a Single-Carbon Stable Isotope Ratio Model for Predicting Added Sugar Intake in Southwest Virginian Adults1,2

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An objective measure of added sugar (AS) and sugar-sweetened beverage (SSB) intake is needed. The δ13C value of finger-stick blood is a novel validated biomarker of AS/SSB intake; however, nonsweetener corn products and animal protein also carry a δ13C value similar to AS sources, which may affect blood δ13C values. The δ15N value of blood has been proposed as a “correction factor” for animal protein intake.


The objectives were to 1) identify foods associated with δ13C and δ15N blood values, 2) determine the contribution of nonsweetener corn to the diet relative to AS intake, and 3) determine if the dual-isotope model (δ13C and δ15N) is a better predictor of AS/SSB intake than δ13C alone.


A cross-sectional sample of southwest Virginian adults (n = 257; aged 42 ± 15 y; 74% overweight/obese) underwent dietary intake assessments and provided finger-stick blood samples, which were analyzed for δ13C and δ15N values by using natural abundance stable isotope mass spectrometry. Statistical analyses included ANOVAs, pairedsamples t tests, and multiple linear regressions.


The mean ± SD daily AS intake was 88 ± 59 g and nonsweetener corn intake was 13 ± 13 g. The mean δ13C valuewas -19.1 ± 0.9%o, which was significantly correlated with AS and SSB intakes (r = 0.32 and 0.39, respectively; P ≤ 0.01). The δ13C value and nonsweetener corn intake and the δ15N value and animal protein intake were not correlated. AS intake was significantly greater than nonsweetener corn intake (mean difference = 76.2 ± 57.2 g; P ≤ 0.001). The δ13C value was predictive of AS/SSB intake (β range: 0.28-0.35; P ≤ 0.01); however, δ15N was not predictive and minimal increases in R2 values were observed when the δ15N value was added to the model.


The data do not provide evidence that the dual-isotope method is superior for predicting AS/SSB intakes within a southwest Virginian population. Our results support the potential of the δ13C value of finger-stick blood to serve as an objective measure of AS/SSB intake. This trial was registered at clinicaltrials.gov as NCT02193009. J Nutr 2015;145:1362-9.

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