The Natural 13C Abundance of Plasma Glucose Is a Useful Biomarker of Recent Dietary Caloric Sweetener Intake

There is a need for objective biomarkers of dietary intake, because self-reporting is often subject to bias. We tested the validity of a biomarker for the fraction of dietary carbohydrate (CHO) from cane sugar and high fructose corn syrup (C-4 sugars) using natural C-13 abundance of plasma glucose. In a randomized, single-blinded, crossover design, 5 participants consumed 3 weight-maintaining diets for 7 d, with a 2-wk washout between diet periods. Diets differed in the fraction of total CHO energy from C-4 sugars (5, 16, or 32%). During each diet period, blood samples were drawn at hours 0800 and 1600 on d 1, 3, and 5 and at 0800, 1000, 1200, 1400, and 1600 on d 7. The delta C-13 abundance of plasma glucose was analyzed via GC-isotope ratio MS. Within each diet period, delta C-13 abundance of the 0800 fasting glucose did not change from baseline with increasing time during a diet period; however, there was a strong positive correlation (R-2 = 0.89) between delta C-13 abundance of the glucose concentration at 1000 on d 7 and the percent of breakfast CHO from C-4 sugars. Also, delta C-13 abundance of the combined plasma glucose samples on d 7 demonstrated a strong positive correlation (R-2 = 0.90) with the percent of total daily CHO from C-4 sugars. The natural delta C-13 abundance of postprandial plasma glucose relative to dietary C-4 CHO content was a valid biomarker for contributions of C-4 caloric sweeteners from the previous meal. J. Nutr. 140: 333-337, 2010.