Carbon and Nitrogen Stable Isotope Ratios Predict Intake of Sweeteners in a Yup'ik Study Population

Abstract

The carbon isotope ratio (δ¹³C) is elevated in corn- and cane sugar-based foods and has recently shown associations with sweetener intake in multiple U.S. populations. However, a high carbon isotope ratio is not specific to corn- and sugar cane-based sweeteners, as other foods, including meats and fish, also have elevated δ¹³C. This study examines whether the inclusion of a second marker, the nitrogen isotope ratio (δ¹⁵N), can control for confounding dietary effects on δ¹³C and improve the validity of isotopic markers of sweetener intake. The study participants are from the Yup'ik population of southwest Alaska and consume large and variable amounts of fish and marine mammals known to have elevated carbon and nitrogen isotope ratios. Sixty-eight participants completed 4 weekly 24-h recalls followed by a blood draw. RBC δ¹³C and δ¹⁵N were used to predict sweetener intake, including total sugars, added sugars, and sugar-sweetened beverages. A model including both δ¹³C and δ¹⁵N explained more than 3 times as much of the variation in sweetener intake than did a model using only δ¹³C. Because carbon and nitrogen isotope ratios are simultaneously determined in a single, high-throughput analysis, this dual isotope marker provides a simple method to improve the validity of stable isotope markers of sweetener intake with no additional cost. We anticipate that this multi-isotope approach will have utility in any population where a stable isotope biomarker is elevated in several food groups and there are appropriate "covariate" isotopes to control for intake of foods not of research interest.

The δ13C Value of Fingerstick Blood Is a Valid, Reliable, and Sensitive Biomarker of Sugar-Sweetened Beverage Intake in Children and Adolescents

“…The δ 13 C biomarker demonstrated comparative validity as it was moderately correlated with AS intake, expressed in g and kcal, and SSB intake, expressed in mL and kcal. The association between δ 13 C and SSB intake was stronger than when compared with AS intake, consistent with the literature (29,(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). This is likely explained by SSBs being comprised of 99% corn and cane sweeteners (36), while AS could be derived from a wider variety of sugar sources (i.e., C4 or C3 plants) (35).…”

“…That investigation did not include a direct assessment of dietary intake, but used δ 13 C values from hair samples to demonstrate associations between biomarkerbased estimates of AS intake with carious tooth surfaces. In the present investigation, the biomarker demonstrated strong testretest reliability, similar to findings from previous investigations (29,32). The δ 13 C biomarker demonstrated comparative validity as it was moderately correlated with AS intake, expressed in g and kcal, and SSB intake, expressed in mL and kcal.…”

“…Blood samples were analyzed in triplicate for δ 13 C value via natural abundance stable isotope mass spectrometry (Isoprime; Micromass UK Ltd), as described previously (29). δ 15 N values, measuring the relative abundance of 15 N to 14 N, were also determined and evaluated as possible covariates to control for the potential confounders of meat (i.e., livestock consuming corn feed) consumption on δ 13 C values (32,40). Total variability across the 3 measurements was within 0.04‰.…”

“…Therefore, the consumption of corn and cane sugars and their derivatives is reflected in the δ 13 C value of adult human tissues using a variety of biological sample types, including a minimally invasive fingerstick blood sample (29,35). The δ 13 C AS biomarker has demonstrated promising preliminary evidence of validity and reliability in adults (26,29,(31)(32)(33)35). However, tissue turnover times may vary according to growth stage, which could impact biomarker values (35,36).…”

The Carbon Isotope Ratio of Alanine in Red Blood Cells Is a New Candidate Biomarker of Sugar-Sweetened Beverage Intake

“…A fundamental limitation of blood d 13 C as a measure of sweetener intake is that the carbon in blood occurs primarily in the form of proteins and thus tends to reflect the d 13 C of dietary protein sources. Our group recently showed that using the nitrogen isotope ratio to control for the confounding effects of dietary protein on d 13 C greatly improves its validity in an Alaska Native population (25). Although this approach dramatically improves the validity for sweeteners, it does not control for all dietary confounders, including commercial (cornfed) meat intake.…”